Merge changes from topic 'reviewers-by-email'

* changes:
  Add reviewers by email to REST API and Email sender
  Add reviewer.enableByEmail to ProjectConfig
  Add reviewers by email to NoteDb

Documentation/config-project-config.txt

@@ -291,6 +291,18 @@ Branches not listed in this section will not be included in the mergeability
 check. If the `branchOrder` section is not defined then the mergeability of a
 change into other branches will not be done.
 
+[[reviewer-section]]
+=== reviewer section
+
+Defines config options to adjust a project's reviewer workflow such as enabling
+reviewers and CCs by email.
+
+[[reviewer.enableByEmail]]reviewer.enableByEmail::
++
+A boolean indicating if reviewers and CCs that do not currently have a Gerrit
+account can be added to a change by providing their email address.
+
+Defaults to `false`.
 
 [[file-groups]]
 == The file +groups+

Documentation/rest-api-changes.txt

@@ -2805,6 +2805,41 @@ To confirm the addition of the reviewers, resend the request with the
   }
 ----
 
+If link:config-project-config.html#reviewer.enableByEmail[reviewer.enableByEmail] is set
+for the project, reviewers and CCs are not required to have a Gerrit account. If you POST
+an email address of a reviewer or CC then, they will be added to the change even if they
+don't have a Gerrit account.
+
+If this option is disabled, the request would fail with `400 Bad Request` if the email
+address can't be resolved to an active Gerrit account.
+
+Note that the name is optional so both "un.registered@reviewer.com" and
+"John Doe <un.registered@reviewer.com>" are valid inputs.
+
+Reviewers without Gerrit accounts can only be added on changes visible to anonymous users.
+
+.Request
+----
+  POST /changes/myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940/reviewers HTTP/1.0
+  Content-Type: application/json; charset=UTF-8
+
+  {
+    "reviewer": "John Doe <un.registered@reviewer.com>"
+  }
+----
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+  )]}'
+  {
+    "input": "John Doe <un.registered@reviewer.com>"
+  }
+----
+
 [[delete-reviewer]]
 === Delete Reviewer
 --
@@ -6183,6 +6218,10 @@ In addition `ReviewerInfo` has the following fields:
 |`approvals`   |
 The approvals of the reviewer as a map that maps the label names to the
 approval values ("`-2`", "`-1`", "`0`", "`+1`", "`+2`").
+|`_account_id`   |
+This field is inherited from `AccountInfo` but is optional here if an
+unregistered reviewer was added by email. See
+link:rest-api-changes.html#add-reviewer[add-reviewer] for details.
 |==========================
 
 [[reviewer-input]]

gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/AbstractDaemonTest.java

@@ -88,6 +88,7 @@ import com.google.gerrit.server.group.SystemGroupBackend;
 import com.google.gerrit.server.index.change.ChangeIndex;
 import com.google.gerrit.server.index.change.ChangeIndexCollection;
 import com.google.gerrit.server.index.change.ChangeIndexer;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.mail.send.EmailHeader;
 import com.google.gerrit.server.notedb.ChangeNoteUtil;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -1200,21 +1201,29 @@ public abstract class AbstractDaemonTest {
   }
 
   protected void assertNotifyTo(TestAccount expected) {
+    assertNotifyTo(expected.emailAddress);
+  }
+
+  protected void assertNotifyTo(Address expected) {
     assertThat(sender.getMessages()).hasSize(1);
     Message m = sender.getMessages().get(0);
-    assertThat(m.rcpt()).containsExactly(expected.emailAddress);
+    assertThat(m.rcpt()).containsExactly(expected);
     assertThat(((EmailHeader.AddressList) m.headers().get("To")).getAddressList())
-        .containsExactly(expected.emailAddress);
+        .containsExactly(expected);
     assertThat(m.headers().get("CC").isEmpty()).isTrue();
   }
 
   protected void assertNotifyCc(TestAccount expected) {
+    assertNotifyCc(expected.emailAddress);
+  }
+
+  protected void assertNotifyCc(Address expected) {
     assertThat(sender.getMessages()).hasSize(1);
     Message m = sender.getMessages().get(0);
-    assertThat(m.rcpt()).containsExactly(expected.emailAddress);
+    assertThat(m.rcpt()).containsExactly(expected);
     assertThat(m.headers().get("To").isEmpty()).isTrue();
     assertThat(((EmailHeader.AddressList) m.headers().get("CC")).getAddressList())
-        .containsExactly(expected.emailAddress);
+        .containsExactly(expected);
   }
 
   protected void assertNotifyBcc(TestAccount expected) {

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/ChangeReviewersByEmailIT.java

@@ -0,0 +1,245 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.acceptance.rest.change;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.TruthJUnit.assume;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.NoHttpd;
+import com.google.gerrit.acceptance.PushOneCommit;
+import com.google.gerrit.extensions.api.changes.AddReviewerInput;
+import com.google.gerrit.extensions.api.changes.ReviewInput;
+import com.google.gerrit.extensions.client.ListChangesOption;
+import com.google.gerrit.extensions.client.ReviewerState;
+import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
+import com.google.gerrit.server.git.ProjectConfig;
+import com.google.gerrit.server.mail.Address;
+import com.google.gerrit.testutil.FakeEmailSender.Message;
+import java.util.EnumSet;
+import java.util.List;
+import org.junit.Before;
+import org.junit.Test;
+
+@NoHttpd
+public class ChangeReviewersByEmailIT extends AbstractDaemonTest {
+
+  @Before
+  public void setUp() throws Exception {
+    ProjectConfig cfg = projectCache.checkedGet(project).getConfig();
+    cfg.setEnableReviewerByEmail(true);
+    saveProjectConfig(project, cfg);
+  }
+
+  @Test
+  public void addByEmail() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    for (ReviewerState state : ImmutableList.of(ReviewerState.CC, ReviewerState.REVIEWER)) {
+      PushOneCommit.Result r = createChange();
+
+      AddReviewerInput input = new AddReviewerInput();
+      input.reviewer = toRfcAddressString(acc);
+      input.state = state;
+      gApi.changes().id(r.getChangeId()).addReviewer(input);
+
+      ChangeInfo info =
+          gApi.changes().id(r.getChangeId()).get(EnumSet.of(ListChangesOption.DETAILED_LABELS));
+      assertThat(info.reviewers).isEqualTo(ImmutableMap.of(state, ImmutableList.of(acc)));
+      // All reviewers added by email should be removable
+      assertThat(info.removableReviewers).isEqualTo(ImmutableList.of(acc));
+    }
+  }
+
+  @Test
+  public void removeByEmail() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    for (ReviewerState state : ImmutableList.of(ReviewerState.CC, ReviewerState.REVIEWER)) {
+      PushOneCommit.Result r = createChange();
+
+      AddReviewerInput addInput = new AddReviewerInput();
+      addInput.reviewer = toRfcAddressString(acc);
+      addInput.state = state;
+      gApi.changes().id(r.getChangeId()).addReviewer(addInput);
+
+      gApi.changes().id(r.getChangeId()).reviewer(acc.email).remove();
+
+      ChangeInfo info =
+          gApi.changes().id(r.getChangeId()).get(EnumSet.of(ListChangesOption.DETAILED_LABELS));
+      assertThat(info.reviewers).isEmpty();
+    }
+  }
+
+  @Test
+  public void convertFromCCToReviewer() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    PushOneCommit.Result r = createChange();
+
+    AddReviewerInput addInput = new AddReviewerInput();
+    addInput.reviewer = toRfcAddressString(acc);
+    addInput.state = ReviewerState.CC;
+    gApi.changes().id(r.getChangeId()).addReviewer(addInput);
+
+    AddReviewerInput modifyInput = new AddReviewerInput();
+    modifyInput.reviewer = addInput.reviewer;
+    modifyInput.state = ReviewerState.REVIEWER;
+    gApi.changes().id(r.getChangeId()).addReviewer(modifyInput);
+
+    ChangeInfo info =
+        gApi.changes().id(r.getChangeId()).get(EnumSet.of(ListChangesOption.DETAILED_LABELS));
+    assertThat(info.reviewers)
+        .isEqualTo(ImmutableMap.of(ReviewerState.REVIEWER, ImmutableList.of(acc)));
+  }
+
+  @Test
+  public void addedReviewersGetNotified() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    for (ReviewerState state : ImmutableList.of(ReviewerState.CC, ReviewerState.REVIEWER)) {
+      PushOneCommit.Result r = createChange();
+
+      AddReviewerInput input = new AddReviewerInput();
+      input.reviewer = toRfcAddressString(acc);
+      input.state = state;
+      gApi.changes().id(r.getChangeId()).addReviewer(input);
+
+      List<Message> messages = sender.getMessages();
+      assertThat(messages).hasSize(1);
+      assertThat(messages.get(0).rcpt()).containsExactly(Address.parse(input.reviewer));
+      sender.clear();
+    }
+  }
+
+  @Test
+  public void removingReviewerTriggersNotification() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    for (ReviewerState state : ImmutableList.of(ReviewerState.CC, ReviewerState.REVIEWER)) {
+      PushOneCommit.Result r = createChange();
+
+      AddReviewerInput addInput = new AddReviewerInput();
+      addInput.reviewer = toRfcAddressString(acc);
+      addInput.state = state;
+      gApi.changes().id(r.getChangeId()).addReviewer(addInput);
+
+      // Review change as user
+      ReviewInput reviewInput = new ReviewInput();
+      reviewInput.message = "I have a comment";
+      setApiUser(user);
+      revision(r).review(reviewInput);
+      setApiUser(admin);
+
+      sender.clear();
+
+      // Delete as admin
+      gApi.changes().id(r.getChangeId()).reviewer(addInput.reviewer).remove();
+
+      List<Message> messages = sender.getMessages();
+      assertThat(messages).hasSize(1);
+      assertThat(messages.get(0).rcpt())
+          .containsExactly(Address.parse(addInput.reviewer), user.emailAddress);
+      sender.clear();
+    }
+  }
+
+  @Test
+  public void reviewerAndCCReceiveRegularNotification() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    AccountInfo acc = new AccountInfo("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    for (ReviewerState state : ImmutableList.of(ReviewerState.CC, ReviewerState.REVIEWER)) {
+      PushOneCommit.Result r = createChange();
+
+      AddReviewerInput input = new AddReviewerInput();
+      input.reviewer = toRfcAddressString(acc);
+      input.state = state;
+      gApi.changes().id(r.getChangeId()).addReviewer(input);
+      sender.clear();
+
+      gApi.changes()
+          .id(r.getChangeId())
+          .revision(r.getCommit().name())
+          .review(ReviewInput.approve());
+
+      if (state == ReviewerState.CC) {
+        assertNotifyCc(Address.parse(input.reviewer));
+      } else {
+        assertNotifyTo(Address.parse(input.reviewer));
+      }
+    }
+  }
+
+  @Test
+  public void rejectMissingEmail() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    PushOneCommit.Result r = createChange();
+
+    exception.expect(UnprocessableEntityException.class);
+    exception.expectMessage("email invalid");
+    gApi.changes().id(r.getChangeId()).addReviewer("");
+  }
+
+  @Test
+  public void rejectMalformedEmail() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    PushOneCommit.Result r = createChange();
+
+    exception.expect(UnprocessableEntityException.class);
+    exception.expectMessage("email invalid");
+    gApi.changes().id(r.getChangeId()).addReviewer("Foo Bar <foo.bar@");
+  }
+
+  @Test
+  public void rejectOnNonPublicChange() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+    PushOneCommit.Result r = createDraftChange();
+
+    exception.expect(BadRequestException.class);
+    exception.expectMessage("change is not publicly visible");
+    gApi.changes().id(r.getChangeId()).addReviewer("Foo Bar <foo.bar@gerritcodereview.com>");
+  }
+
+  @Test
+  public void rejectWhenFeatureIsDisabled() throws Exception {
+    assume().that(notesMigration.readChanges()).isTrue();
+
+    ProjectConfig cfg = projectCache.checkedGet(project).getConfig();
+    cfg.setEnableReviewerByEmail(false);
+    saveProjectConfig(project, cfg);
+
+    PushOneCommit.Result r = createChange();
+
+    exception.expect(UnprocessableEntityException.class);
+    exception.expectMessage(
+        "Foo Bar <foo.bar@gerritcodereview.com> does not identify a registered user or group");
+    gApi.changes().id(r.getChangeId()).addReviewer("Foo Bar <foo.bar@gerritcodereview.com>");
+  }
+
+  private static String toRfcAddressString(AccountInfo info) {
+    return (new Address(info.name, info.email)).toString();
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewerInfo.java

@@ -25,6 +25,13 @@ public class ReviewerInfo extends AccountInfo {
    */
   @Nullable public Map<String, String> approvals;
 
+  public static ReviewerInfo byEmail(@Nullable String name, String email) {
+    ReviewerInfo info = new ReviewerInfo();
+    info.name = name;
+    info.email = email;
+    return info;
+  }
+
   public ReviewerInfo(Integer id) {
     super(id);
   }
@@ -33,4 +40,6 @@ public class ReviewerInfo extends AccountInfo {
   public String toString() {
     return username;
   }
+
+  private ReviewerInfo() {}
 }

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/projects/ConfigInfo.java

@@ -31,6 +31,7 @@ public class ConfigInfo {
   public InheritedBooleanInfo enableSignedPush;
   public InheritedBooleanInfo requireSignedPush;
   public InheritedBooleanInfo rejectImplicitMerges;
+  public InheritedBooleanInfo enableReviewerByEmail;
   public MaxObjectSizeLimitInfo maxObjectSizeLimit;
   public SubmitType submitType;
   public ProjectState state;

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/AccountInfo.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.extensions.common;
 
 import java.util.List;
+import java.util.Objects;
 
 public class AccountInfo {
   public Integer _accountId;
@@ -29,4 +30,34 @@ public class AccountInfo {
   public AccountInfo(Integer id) {
     this._accountId = id;
   }
+
+  /** To be used ONLY in connection with unregistered reviewers and CCs. */
+  public AccountInfo(String name, String email) {
+    this.name = name;
+    this.email = email;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o instanceof AccountInfo) {
+      AccountInfo accountInfo = (AccountInfo) o;
+      return Objects.equals(_accountId, accountInfo._accountId)
+          && Objects.equals(name, accountInfo.name)
+          && Objects.equals(email, accountInfo.email)
+          && Objects.equals(secondaryEmails, accountInfo.secondaryEmails)
+          && Objects.equals(username, accountInfo.username)
+          && Objects.equals(avatars, accountInfo.avatars)
+          && Objects.equals(_moreAccounts, accountInfo._moreAccounts)
+          && Objects.equals(status, accountInfo.status);
+    }
+    return false;
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(
+        _accountId, name, email, secondaryEmails, username, avatars, _moreAccounts, status);
+  }
+
+  protected AccountInfo() {}
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/admin/ProjectInfoScreen.java

@@ -86,6 +86,7 @@ public class ProjectInfoScreen extends ProjectScreen {
   private ListBox enableSignedPush;
   private ListBox requireSignedPush;
   private ListBox rejectImplicitMerges;
+  private ListBox enableReviewerByEmail;
   private NpTextBox maxObjectSizeLimit;
   private Label effectiveMaxObjectSizeLimit;
   private Map<String, Map<String, HasEnabled>> pluginConfigWidgets;
@@ -191,6 +192,7 @@ public class ProjectInfoScreen extends ProjectScreen {
     requireChangeID.setEnabled(isOwner);
     rejectImplicitMerges.setEnabled(isOwner);
     maxObjectSizeLimit.setEnabled(isOwner);
+    enableReviewerByEmail.setEnabled(isOwner);
 
     if (pluginConfigWidgets != null) {
       for (Map<String, HasEnabled> widgetMap : pluginConfigWidgets.values()) {
@@ -264,6 +266,10 @@ public class ProjectInfoScreen extends ProjectScreen {
     saveEnabler.listenTo(rejectImplicitMerges);
     grid.addHtml(AdminConstants.I.rejectImplicitMerges(), rejectImplicitMerges);
 
+    enableReviewerByEmail = newInheritedBooleanBox();
+    saveEnabler.listenTo(enableReviewerByEmail);
+    grid.addHtml(AdminConstants.I.rejectImplicitMerges(), enableReviewerByEmail);
+
     maxObjectSizeLimit = new NpTextBox();
     saveEnabler.listenTo(maxObjectSizeLimit);
     effectiveMaxObjectSizeLimit = new Label();
@@ -395,6 +401,7 @@ public class ProjectInfoScreen extends ProjectScreen {
       setBool(requireSignedPush, result.requireSignedPush());
     }
     setBool(rejectImplicitMerges, result.rejectImplicitMerges());
+    setBool(enableReviewerByEmail, result.enableReviewerByEmail());
     setSubmitType(result.submitType());
     setState(result.state());
     maxObjectSizeLimit.setText(result.maxObjectSizeLimit().configuredValue());

gerrit-gwtui/src/main/java/com/google/gerrit/client/projects/ConfigInfo.java

@@ -57,6 +57,9 @@ public class ConfigInfo extends JavaScriptObject {
   public final native InheritedBooleanInfo rejectImplicitMerges()
       /*-{ return this.reject_implicit_merges; }-*/ ;
 
+  public final native InheritedBooleanInfo enableReviewerByEmail()
+      /*-{ return this.enable_reviewer_by_email; }-*/ ;
+
   public final SubmitType submitType() {
     return SubmitType.valueOf(submitTypeRaw());
   }

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/Project.java

@@ -99,6 +99,8 @@ public final class Project {
 
   protected InheritableBoolean rejectImplicitMerges;
 
+  protected InheritableBoolean enableReviewerByEmail;
+
   protected Project() {}
 
   public Project(Project.NameKey nameKey) {
@@ -112,6 +114,7 @@ public final class Project {
     createNewChangeForAllNotInTarget = InheritableBoolean.INHERIT;
     enableSignedPush = InheritableBoolean.INHERIT;
     requireSignedPush = InheritableBoolean.INHERIT;
+    enableReviewerByEmail = InheritableBoolean.INHERIT;
   }
 
   public Project.NameKey getNameKey() {
@@ -154,6 +157,10 @@ public final class Project {
     return rejectImplicitMerges;
   }
 
+  public InheritableBoolean getEnableReviewerByEmail() {
+    return enableReviewerByEmail;
+  }
+
   public void setUseContributorAgreements(final InheritableBoolean u) {
     useContributorAgreements = u;
   }

gerrit-server/src/main/java/com/google/gerrit/server/ReviewerByEmailSet.java

@@ -0,0 +1,79 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Table;
+import com.google.gerrit.server.mail.Address;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
+import java.sql.Timestamp;
+
+/**
+ * Set of reviewers on a change that do not have a Gerrit account and were added by email instead.
+ *
+ * <p>A given account may appear in multiple states and at different timestamps. No reviewers with
+ * state {@link ReviewerStateInternal#REMOVED} are ever exposed by this interface.
+ */
+public class ReviewerByEmailSet {
+  private static final ReviewerByEmailSet EMPTY = new ReviewerByEmailSet(ImmutableTable.of());
+
+  public static ReviewerByEmailSet fromTable(
+      Table<ReviewerStateInternal, Address, Timestamp> table) {
+    return new ReviewerByEmailSet(table);
+  }
+
+  public static ReviewerByEmailSet empty() {
+    return EMPTY;
+  }
+
+  private final ImmutableTable<ReviewerStateInternal, Address, Timestamp> table;
+  private ImmutableSet<Address> users;
+
+  private ReviewerByEmailSet(Table<ReviewerStateInternal, Address, Timestamp> table) {
+    this.table = ImmutableTable.copyOf(table);
+  }
+
+  public ImmutableSet<Address> all() {
+    if (users == null) {
+      // Idempotent and immutable, don't bother locking.
+      users = ImmutableSet.copyOf(table.columnKeySet());
+    }
+    return users;
+  }
+
+  public ImmutableSet<Address> byState(ReviewerStateInternal state) {
+    return table.row(state).keySet();
+  }
+
+  public ImmutableTable<ReviewerStateInternal, Address, Timestamp> asTable() {
+    return table;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return (o instanceof ReviewerByEmailSet) && table.equals(((ReviewerByEmailSet) o).table);
+  }
+
+  @Override
+  public int hashCode() {
+    return table.hashCode();
+  }
+
+  @Override
+  public String toString() {
+    return getClass().getSimpleName() + table;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java

@@ -108,6 +108,7 @@ import com.google.gerrit.server.git.LabelNormalizer;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.index.change.ChangeField;
 import com.google.gerrit.server.index.change.ChangeIndexCollection;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
@@ -531,6 +532,12 @@ public class ChangeJson {
           cd.reviewers().asTable().rowMap().entrySet()) {
         out.reviewers.put(e.getKey().asReviewerState(), toAccountInfo(e.getValue().keySet()));
       }
+      // TODO(hiesel) Load from ChangeData instead after the data was added there
+      for (Map.Entry<ReviewerStateInternal, Map<Address, Timestamp>> e :
+          cd.notes().getReviewersByEmail().asTable().rowMap().entrySet()) {
+        out.reviewers.put(
+            e.getKey().asReviewerState(), toAccountInfoByEmail(e.getValue().keySet()));
+      }
 
       out.removableReviewers = removableReviewers(ctl, out);
     }
@@ -1075,12 +1082,14 @@ public class ChangeJson {
     Collection<AccountInfo> ccs = out.reviewers.get(ReviewerState.CC);
     if (ccs != null) {
       for (AccountInfo ai : ccs) {
+        if (ai._accountId != null) {
           Account.Id id = new Account.Id(ai._accountId);
           if (ctl.canRemoveReviewer(id, 0)) {
             removable.add(id);
           }
         }
       }
+    }
 
     // Subtract any reviewers with non-removable approvals from the "removable"
     // set. This also subtracts any CCs that for some reason also hold
@@ -1091,6 +1100,14 @@ public class ChangeJson {
     for (Account.Id id : removable) {
       result.add(accountLoader.get(id));
     }
+    // Reviewers added by email are always removable
+    for (Collection<AccountInfo> infos : out.reviewers.values()) {
+      for (AccountInfo info : infos) {
+        if (info._accountId == null) {
+          result.add(info);
+        }
+      }
+    }
     return result;
   }
 
@@ -1102,6 +1119,14 @@ public class ChangeJson {
         .collect(toList());
   }
 
+  private Collection<AccountInfo> toAccountInfoByEmail(Collection<Address> addresses) {
+    return addresses
+        .stream()
+        .map(a -> new AccountInfo(a.getName(), a.getEmail()))
+        .sorted(AccountInfoComparator.ORDER_NULLS_FIRST)
+        .collect(toList());
+  }
+
   @Nullable
   private Repository openRepoIfNecessary(ChangeControl ctl) throws IOException {
     if (has(ALL_COMMITS) || has(CURRENT_COMMIT) || has(COMMIT_FOOTERS)) {

gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteReviewer.java

@@ -14,92 +14,38 @@
 
 package com.google.gerrit.server.change;
 
-import com.google.common.collect.Iterables;
 import com.google.gerrit.common.TimeUtil;
-import com.google.gerrit.common.data.LabelType;
-import com.google.gerrit.common.data.LabelTypes;
 import com.google.gerrit.extensions.api.changes.DeleteReviewerInput;
 import com.google.gerrit.extensions.api.changes.NotifyHandling;
-import com.google.gerrit.extensions.restapi.AuthException;
-import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestModifyView;
-import com.google.gerrit.reviewdb.client.Account;
-import com.google.gerrit.reviewdb.client.Change;
-import com.google.gerrit.reviewdb.client.ChangeMessage;
-import com.google.gerrit.reviewdb.client.PatchSet;
-import com.google.gerrit.reviewdb.client.PatchSetApproval;
-import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
-import com.google.gerrit.reviewdb.server.ReviewDbUtil;
-import com.google.gerrit.server.ApprovalsUtil;
-import com.google.gerrit.server.ChangeMessagesUtil;
-import com.google.gerrit.server.IdentifiedUser;
-import com.google.gerrit.server.PatchSetUtil;
-import com.google.gerrit.server.extensions.events.ReviewerDeleted;
-import com.google.gerrit.server.mail.send.DeleteReviewerSender;
-import com.google.gerrit.server.notedb.ChangeUpdate;
-import com.google.gerrit.server.notedb.NoteDbChangeState.PrimaryStorage;
-import com.google.gerrit.server.notedb.NotesMigration;
 import com.google.gerrit.server.update.BatchUpdate;
 import com.google.gerrit.server.update.BatchUpdateOp;
-import com.google.gerrit.server.update.BatchUpdateReviewDb;
-import com.google.gerrit.server.update.ChangeContext;
-import com.google.gerrit.server.update.Context;
 import com.google.gerrit.server.update.UpdateException;
-import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 @Singleton
 public class DeleteReviewer implements RestModifyView<ReviewerResource, DeleteReviewerInput> {
-  private static final Logger log = LoggerFactory.getLogger(DeleteReviewer.class);
 
   private final Provider<ReviewDb> dbProvider;
-  private final ApprovalsUtil approvalsUtil;
-  private final PatchSetUtil psUtil;
-  private final ChangeMessagesUtil cmUtil;
   private final BatchUpdate.Factory batchUpdateFactory;
-  private final IdentifiedUser.GenericFactory userFactory;
+  private final DeleteReviewerOp.Factory deleteReviewerOpFactory;
-  private final ReviewerDeleted reviewerDeleted;
+  private final DeleteReviewerByEmailOp.Factory deleteReviewerByEmailOpFactory;
-  private final Provider<IdentifiedUser> user;
-  private final DeleteReviewerSender.Factory deleteReviewerSenderFactory;
-  private final NotesMigration migration;
-  private final NotifyUtil notifyUtil;
 
   @Inject
   DeleteReviewer(
       Provider<ReviewDb> dbProvider,
-      ApprovalsUtil approvalsUtil,
-      PatchSetUtil psUtil,
-      ChangeMessagesUtil cmUtil,
       BatchUpdate.Factory batchUpdateFactory,
-      IdentifiedUser.GenericFactory userFactory,
+      DeleteReviewerOp.Factory deleteReviewerOpFactory,
-      ReviewerDeleted reviewerDeleted,
+      DeleteReviewerByEmailOp.Factory deleteReviewerByEmailOpFactory) {
-      Provider<IdentifiedUser> user,
-      DeleteReviewerSender.Factory deleteReviewerSenderFactory,
-      NotesMigration migration,
-      NotifyUtil notifyUtil) {
     this.dbProvider = dbProvider;
-    this.approvalsUtil = approvalsUtil;
-    this.psUtil = psUtil;
-    this.cmUtil = cmUtil;
     this.batchUpdateFactory = batchUpdateFactory;
-    this.userFactory = userFactory;
+    this.deleteReviewerOpFactory = deleteReviewerOpFactory;
-    this.reviewerDeleted = reviewerDeleted;
+    this.deleteReviewerByEmailOpFactory = deleteReviewerByEmailOpFactory;
-    this.user = user;
-    this.deleteReviewerSenderFactory = deleteReviewerSenderFactory;
-    this.migration = migration;
-    this.notifyUtil = notifyUtil;
   }
 
   @Override
@@ -118,151 +64,15 @@ public class DeleteReviewer implements RestModifyView<ReviewerResource, DeleteRe
             rsrc.getChangeResource().getProject(),
             rsrc.getChangeResource().getUser(),
             TimeUtil.nowTs())) {
-      Op op = new Op(rsrc.getReviewerUser().getAccount(), input);
+      BatchUpdateOp op;
+      if (rsrc.isByEmail()) {
+        op = deleteReviewerByEmailOpFactory.create(rsrc.getReviewerByEmail(), input);
+      } else {
+        op = deleteReviewerOpFactory.create(rsrc.getReviewerUser().getAccount(), input);
+      }
       bu.addOp(rsrc.getChange().getId(), op);
       bu.execute();
     }
-
     return Response.none();
   }
-
-  private class Op implements BatchUpdateOp {
-    private final Account reviewer;
-    private final DeleteReviewerInput input;
-    ChangeMessage changeMessage;
-    Change currChange;
-    PatchSet currPs;
-    Map<String, Short> newApprovals = new HashMap<>();
-    Map<String, Short> oldApprovals = new HashMap<>();
-
-    Op(Account reviewerAccount, DeleteReviewerInput input) {
-      this.reviewer = reviewerAccount;
-      this.input = input;
-    }
-
-    @Override
-    public boolean updateChange(ChangeContext ctx)
-        throws AuthException, ResourceNotFoundException, OrmException {
-      Account.Id reviewerId = reviewer.getId();
-      if (!approvalsUtil.getReviewers(ctx.getDb(), ctx.getNotes()).all().contains(reviewerId)) {
-        throw new ResourceNotFoundException();
-      }
-      currChange = ctx.getChange();
-      currPs = psUtil.current(ctx.getDb(), ctx.getNotes());
-
-      LabelTypes labelTypes = ctx.getControl().getLabelTypes();
-      // removing a reviewer will remove all her votes
-      for (LabelType lt : labelTypes.getLabelTypes()) {
-        newApprovals.put(lt.getName(), (short) 0);
-      }
-
-      StringBuilder msg = new StringBuilder();
-      msg.append("Removed reviewer " + reviewer.getFullName());
-      StringBuilder removedVotesMsg = new StringBuilder();
-      removedVotesMsg.append(" with the following votes:\n\n");
-      List<PatchSetApproval> del = new ArrayList<>();
-      boolean votesRemoved = false;
-      for (PatchSetApproval a : approvals(ctx, reviewerId)) {
-        if (ctx.getControl().canRemoveReviewer(a)) {
-          del.add(a);
-          if (a.getPatchSetId().equals(currPs.getId()) && a.getValue() != 0) {
-            oldApprovals.put(a.getLabel(), a.getValue());
-            removedVotesMsg
-                .append("* ")
-                .append(a.getLabel())
-                .append(formatLabelValue(a.getValue()))
-                .append(" by ")
-                .append(userFactory.create(a.getAccountId()).getNameEmail())
-                .append("\n");
-            votesRemoved = true;
-          }
-        } else {
-          throw new AuthException("delete reviewer not permitted");
-        }
-      }
-
-      if (votesRemoved) {
-        msg.append(removedVotesMsg);
-      } else {
-        msg.append(".");
-      }
-      ctx.getDb().patchSetApprovals().delete(del);
-      ChangeUpdate update = ctx.getUpdate(currPs.getId());
-      update.removeReviewer(reviewerId);
-
-      changeMessage =
-          ChangeMessagesUtil.newMessage(
-              ctx, msg.toString(), ChangeMessagesUtil.TAG_DELETE_REVIEWER);
-      cmUtil.addChangeMessage(ctx.getDb(), update, changeMessage);
-
-      return true;
-    }
-
-    @Override
-    public void postUpdate(Context ctx) {
-      if (NotifyUtil.shouldNotify(input.notify, input.notifyDetails)) {
-        emailReviewers(ctx.getProject(), currChange, changeMessage);
-      }
-      reviewerDeleted.fire(
-          currChange,
-          currPs,
-          reviewer,
-          ctx.getAccount(),
-          changeMessage.getMessage(),
-          newApprovals,
-          oldApprovals,
-          input.notify,
-          ctx.getWhen());
-    }
-
-    private Iterable<PatchSetApproval> approvals(ChangeContext ctx, Account.Id accountId)
-        throws OrmException {
-      Change.Id changeId = ctx.getNotes().getChangeId();
-      Iterable<PatchSetApproval> approvals;
-      PrimaryStorage r = PrimaryStorage.of(ctx.getChange());
-
-      if (migration.readChanges() && r == PrimaryStorage.REVIEW_DB) {
-        // Because NoteDb and ReviewDb have different semantics for zero-value
-        // approvals, we must fall back to ReviewDb as the source of truth here.
-        ReviewDb db = ctx.getDb();
-
-        if (db instanceof BatchUpdateReviewDb) {
-          db = ((BatchUpdateReviewDb) db).unsafeGetDelegate();
-        }
-        db = ReviewDbUtil.unwrapDb(db);
-        approvals = db.patchSetApprovals().byChange(changeId);
-      } else {
-        approvals = approvalsUtil.byChange(ctx.getDb(), ctx.getNotes()).values();
-      }
-
-      return Iterables.filter(approvals, psa -> accountId.equals(psa.getAccountId()));
-    }
-
-    private String formatLabelValue(short value) {
-      if (value > 0) {
-        return "+" + value;
-      }
-      return Short.toString(value);
-    }
-
-    private void emailReviewers(
-        Project.NameKey projectName, Change change, ChangeMessage changeMessage) {
-      Account.Id userId = user.get().getAccountId();
-      if (userId.equals(reviewer.getId())) {
-        // The user knows they removed themselves, don't bother emailing them.
-        return;
-      }
-      try {
-        DeleteReviewerSender cm = deleteReviewerSenderFactory.create(projectName, change.getId());
-        cm.setFrom(userId);
-        cm.addReviewers(Collections.singleton(reviewer.getId()));
-        cm.setChangeMessage(changeMessage.getMessage(), changeMessage.getWrittenOn());
-        cm.setNotify(input.notify);
-        cm.setAccountsToNotify(notifyUtil.resolveAccounts(input.notifyDetails));
-        cm.send();
-      } catch (Exception err) {
-        log.error("Cannot email update for change " + change.getId(), err);
-      }
-    }
-  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteReviewerByEmailOp.java

@@ -0,0 +1,96 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import com.google.gerrit.extensions.api.changes.DeleteReviewerInput;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.ChangeMessage;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.ChangeUtil;
+import com.google.gerrit.server.mail.Address;
+import com.google.gerrit.server.mail.send.DeleteReviewerSender;
+import com.google.gerrit.server.update.BatchUpdateOp;
+import com.google.gerrit.server.update.ChangeContext;
+import com.google.gerrit.server.update.Context;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.assistedinject.Assisted;
+import java.util.Collections;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DeleteReviewerByEmailOp implements BatchUpdateOp {
+  private static final Logger log = LoggerFactory.getLogger(DeleteReviewer.class);
+
+  public interface Factory {
+    DeleteReviewerByEmailOp create(Address reviewer, DeleteReviewerInput input);
+  }
+
+  private final DeleteReviewerSender.Factory deleteReviewerSenderFactory;
+  private final NotifyUtil notifyUtil;
+  private final Address reviewer;
+  private final DeleteReviewerInput input;
+
+  private ChangeMessage changeMessage;
+  private Change.Id changeId;
+
+  @Inject
+  DeleteReviewerByEmailOp(
+      DeleteReviewerSender.Factory deleteReviewerSenderFactory,
+      NotifyUtil notifyUtil,
+      @Assisted Address reviewer,
+      @Assisted DeleteReviewerInput input) {
+    this.deleteReviewerSenderFactory = deleteReviewerSenderFactory;
+    this.notifyUtil = notifyUtil;
+    this.reviewer = reviewer;
+    this.input = input;
+  }
+
+  @Override
+  public boolean updateChange(ChangeContext ctx) throws OrmException {
+    changeId = ctx.getChange().getId();
+    PatchSet.Id psId = ctx.getChange().currentPatchSetId();
+    String msg = "Removed reviewer " + reviewer;
+    changeMessage =
+        new ChangeMessage(
+            new ChangeMessage.Key(changeId, ChangeUtil.messageUuid()),
+            ctx.getAccountId(),
+            ctx.getWhen(),
+            psId);
+    changeMessage.setMessage(msg);
+
+    ctx.getUpdate(psId).setChangeMessage(msg);
+    ctx.getUpdate(psId).removeReviewerByEmail(reviewer);
+    return true;
+  }
+
+  @Override
+  public void postUpdate(Context ctx) {
+    if (!NotifyUtil.shouldNotify(input.notify, input.notifyDetails)) {
+      return;
+    }
+    try {
+      DeleteReviewerSender cm = deleteReviewerSenderFactory.create(ctx.getProject(), changeId);
+      cm.setFrom(ctx.getAccountId());
+      cm.addReviewersByEmail(Collections.singleton(reviewer));
+      cm.setChangeMessage(changeMessage.getMessage(), changeMessage.getWrittenOn());
+      cm.setNotify(input.notify);
+      cm.setAccountsToNotify(notifyUtil.resolveAccounts(input.notifyDetails));
+      cm.send();
+    } catch (Exception err) {
+      log.error("Cannot email update for change " + changeId, err);
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteReviewerOp.java

@@ -0,0 +1,232 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.change;
+
+import com.google.common.collect.Iterables;
+import com.google.gerrit.common.data.LabelType;
+import com.google.gerrit.common.data.LabelTypes;
+import com.google.gerrit.extensions.api.changes.DeleteReviewerInput;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.ChangeMessage;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.reviewdb.server.ReviewDbUtil;
+import com.google.gerrit.server.ApprovalsUtil;
+import com.google.gerrit.server.ChangeMessagesUtil;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.extensions.events.ReviewerDeleted;
+import com.google.gerrit.server.mail.send.DeleteReviewerSender;
+import com.google.gerrit.server.notedb.ChangeUpdate;
+import com.google.gerrit.server.notedb.NoteDbChangeState.PrimaryStorage;
+import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.update.BatchUpdateOp;
+import com.google.gerrit.server.update.BatchUpdateReviewDb;
+import com.google.gerrit.server.update.ChangeContext;
+import com.google.gerrit.server.update.Context;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.assistedinject.Assisted;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class DeleteReviewerOp implements BatchUpdateOp {
+  private static final Logger log = LoggerFactory.getLogger(DeleteReviewer.class);
+
+  public interface Factory {
+    DeleteReviewerOp create(Account reviewerAccount, DeleteReviewerInput input);
+  }
+
+  private final ApprovalsUtil approvalsUtil;
+  private final PatchSetUtil psUtil;
+  private final ChangeMessagesUtil cmUtil;
+  private final IdentifiedUser.GenericFactory userFactory;
+  private final ReviewerDeleted reviewerDeleted;
+  private final Provider<IdentifiedUser> user;
+  private final DeleteReviewerSender.Factory deleteReviewerSenderFactory;
+  private final NotesMigration migration;
+  private final NotifyUtil notifyUtil;
+
+  private final Account reviewer;
+  private final DeleteReviewerInput input;
+
+  ChangeMessage changeMessage;
+  Change currChange;
+  PatchSet currPs;
+  Map<String, Short> newApprovals = new HashMap<>();
+  Map<String, Short> oldApprovals = new HashMap<>();
+
+  @Inject
+  DeleteReviewerOp(
+      ApprovalsUtil approvalsUtil,
+      PatchSetUtil psUtil,
+      ChangeMessagesUtil cmUtil,
+      IdentifiedUser.GenericFactory userFactory,
+      ReviewerDeleted reviewerDeleted,
+      Provider<IdentifiedUser> user,
+      DeleteReviewerSender.Factory deleteReviewerSenderFactory,
+      NotesMigration migration,
+      NotifyUtil notifyUtil,
+      @Assisted Account reviewerAccount,
+      @Assisted DeleteReviewerInput input) {
+    this.approvalsUtil = approvalsUtil;
+    this.psUtil = psUtil;
+    this.cmUtil = cmUtil;
+    this.userFactory = userFactory;
+    this.reviewerDeleted = reviewerDeleted;
+    this.user = user;
+    this.deleteReviewerSenderFactory = deleteReviewerSenderFactory;
+    this.migration = migration;
+    this.notifyUtil = notifyUtil;
+
+    this.reviewer = reviewerAccount;
+    this.input = input;
+  }
+
+  @Override
+  public boolean updateChange(ChangeContext ctx)
+      throws AuthException, ResourceNotFoundException, OrmException {
+    Account.Id reviewerId = reviewer.getId();
+    if (!approvalsUtil.getReviewers(ctx.getDb(), ctx.getNotes()).all().contains(reviewerId)) {
+      throw new ResourceNotFoundException();
+    }
+    currChange = ctx.getChange();
+    currPs = psUtil.current(ctx.getDb(), ctx.getNotes());
+
+    LabelTypes labelTypes = ctx.getControl().getLabelTypes();
+    // removing a reviewer will remove all her votes
+    for (LabelType lt : labelTypes.getLabelTypes()) {
+      newApprovals.put(lt.getName(), (short) 0);
+    }
+
+    StringBuilder msg = new StringBuilder();
+    msg.append("Removed reviewer " + reviewer.getFullName());
+    StringBuilder removedVotesMsg = new StringBuilder();
+    removedVotesMsg.append(" with the following votes:\n\n");
+    List<PatchSetApproval> del = new ArrayList<>();
+    boolean votesRemoved = false;
+    for (PatchSetApproval a : approvals(ctx, reviewerId)) {
+      if (ctx.getControl().canRemoveReviewer(a)) {
+        del.add(a);
+        if (a.getPatchSetId().equals(currPs.getId()) && a.getValue() != 0) {
+          oldApprovals.put(a.getLabel(), a.getValue());
+          removedVotesMsg
+              .append("* ")
+              .append(a.getLabel())
+              .append(formatLabelValue(a.getValue()))
+              .append(" by ")
+              .append(userFactory.create(a.getAccountId()).getNameEmail())
+              .append("\n");
+          votesRemoved = true;
+        }
+      } else {
+        throw new AuthException("delete reviewer not permitted");
+      }
+    }
+
+    if (votesRemoved) {
+      msg.append(removedVotesMsg);
+    } else {
+      msg.append(".");
+    }
+    ctx.getDb().patchSetApprovals().delete(del);
+    ChangeUpdate update = ctx.getUpdate(currPs.getId());
+    update.removeReviewer(reviewerId);
+
+    changeMessage =
+        ChangeMessagesUtil.newMessage(ctx, msg.toString(), ChangeMessagesUtil.TAG_DELETE_REVIEWER);
+    cmUtil.addChangeMessage(ctx.getDb(), update, changeMessage);
+
+    return true;
+  }
+
+  @Override
+  public void postUpdate(Context ctx) {
+    if (NotifyUtil.shouldNotify(input.notify, input.notifyDetails)) {
+      emailReviewers(ctx.getProject(), currChange, changeMessage);
+    }
+    reviewerDeleted.fire(
+        currChange,
+        currPs,
+        reviewer,
+        ctx.getAccount(),
+        changeMessage.getMessage(),
+        newApprovals,
+        oldApprovals,
+        input.notify,
+        ctx.getWhen());
+  }
+
+  private Iterable<PatchSetApproval> approvals(ChangeContext ctx, Account.Id accountId)
+      throws OrmException {
+    Change.Id changeId = ctx.getNotes().getChangeId();
+    Iterable<PatchSetApproval> approvals;
+    PrimaryStorage r = PrimaryStorage.of(ctx.getChange());
+
+    if (migration.readChanges() && r == PrimaryStorage.REVIEW_DB) {
+      // Because NoteDb and ReviewDb have different semantics for zero-value
+      // approvals, we must fall back to ReviewDb as the source of truth here.
+      ReviewDb db = ctx.getDb();
+
+      if (db instanceof BatchUpdateReviewDb) {
+        db = ((BatchUpdateReviewDb) db).unsafeGetDelegate();
+      }
+      db = ReviewDbUtil.unwrapDb(db);
+      approvals = db.patchSetApprovals().byChange(changeId);
+    } else {
+      approvals = approvalsUtil.byChange(ctx.getDb(), ctx.getNotes()).values();
+    }
+
+    return Iterables.filter(approvals, psa -> accountId.equals(psa.getAccountId()));
+  }
+
+  private String formatLabelValue(short value) {
+    if (value > 0) {
+      return "+" + value;
+    }
+    return Short.toString(value);
+  }
+
+  private void emailReviewers(
+      Project.NameKey projectName, Change change, ChangeMessage changeMessage) {
+    Account.Id userId = user.get().getAccountId();
+    if (userId.equals(reviewer.getId())) {
+      // The user knows they removed themselves, don't bother emailing them.
+      return;
+    }
+    try {
+      DeleteReviewerSender cm = deleteReviewerSenderFactory.create(projectName, change.getId());
+      cm.setFrom(userId);
+      cm.addReviewers(Collections.singleton(reviewer.getId()));
+      cm.setChangeMessage(changeMessage.getMessage(), changeMessage.getWrittenOn());
+      cm.setNotify(input.notify);
+      cm.setAccountsToNotify(notifyUtil.resolveAccounts(input.notifyDetails));
+      cm.send();
+    } catch (Exception err) {
+      log.error("Cannot email update for change " + change.getId(), err);
+    }
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/change/ListReviewers.java

@@ -19,6 +19,7 @@ import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
+import com.google.gerrit.server.mail.Address;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -48,11 +49,16 @@ class ListReviewers implements RestReadView<ChangeResource> {
 
   @Override
   public List<ReviewerInfo> apply(ChangeResource rsrc) throws OrmException {
-    Map<Account.Id, ReviewerResource> reviewers = new LinkedHashMap<>();
+    Map<String, ReviewerResource> reviewers = new LinkedHashMap<>();
     ReviewDb db = dbProvider.get();
     for (Account.Id accountId : approvalsUtil.getReviewers(db, rsrc.getNotes()).all()) {
-      if (!reviewers.containsKey(accountId)) {
+      if (!reviewers.containsKey(accountId.toString())) {
-        reviewers.put(accountId, resourceFactory.create(rsrc, accountId));
+        reviewers.put(accountId.toString(), resourceFactory.create(rsrc, accountId));
+      }
+    }
+    for (Address adr : rsrc.getNotes().getReviewersByEmail().all()) {
+      if (!reviewers.containsKey(adr.toString())) {
+        reviewers.put(adr.toString(), new ReviewerResource(rsrc, adr));
       }
     }
     return json.format(reviewers.values());

gerrit-server/src/main/java/com/google/gerrit/server/change/ListRevisionReviewers.java

@@ -20,6 +20,7 @@ import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
+import com.google.gerrit.server.mail.Address;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -54,11 +55,16 @@ class ListRevisionReviewers implements RestReadView<RevisionResource> {
       throw new MethodNotAllowedException("Cannot list reviewers on non-current patch set");
     }
 
-    Map<Account.Id, ReviewerResource> reviewers = new LinkedHashMap<>();
+    Map<String, ReviewerResource> reviewers = new LinkedHashMap<>();
     ReviewDb db = dbProvider.get();
     for (Account.Id accountId : approvalsUtil.getReviewers(db, rsrc.getNotes()).all()) {
-      if (!reviewers.containsKey(accountId)) {
+      if (!reviewers.containsKey(accountId.toString())) {
-        reviewers.put(accountId, resourceFactory.create(rsrc, accountId));
+        reviewers.put(accountId.toString(), resourceFactory.create(rsrc, accountId));
+      }
+    }
+    for (Address address : rsrc.getNotes().getReviewersByEmail().all()) {
+      if (!reviewers.containsKey(address.toString())) {
+        reviewers.put(address.toString(), new ReviewerResource(rsrc, address));
       }
     }
     return json.format(reviewers.values());

gerrit-server/src/main/java/com/google/gerrit/server/change/Module.java

@@ -161,5 +161,7 @@ public class Module extends RestApiModule {
     factory(SetAssigneeOp.Factory.class);
     factory(SetHashtagsOp.Factory.class);
     factory(ChangeResource.Factory.class);
+    factory(DeleteReviewerOp.Factory.class);
+    factory(DeleteReviewerByEmailOp.Factory.class);
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java

@@ -86,6 +86,7 @@ import com.google.gerrit.server.PatchSetUtil;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.account.AccountsCollection;
 import com.google.gerrit.server.extensions.events.CommentAdded;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ChangeUpdate;
 import com.google.gerrit.server.notedb.NotesMigration;
@@ -313,14 +314,18 @@ public class PostReview implements RestModifyView<RevisionResource, ReviewInput>
       ListMultimap<RecipientType, Account.Id> accountsToNotify) {
     List<Account.Id> to = new ArrayList<>();
     List<Account.Id> cc = new ArrayList<>();
+    List<Address> toByEmail = new ArrayList<>();
+    List<Address> ccByEmail = new ArrayList<>();
     for (PostReviewers.Addition addition : reviewerAdditions) {
       if (addition.op.state == ReviewerState.REVIEWER) {
         to.addAll(addition.op.reviewers.keySet());
+        toByEmail.addAll(addition.op.reviewersByEmail);
       } else if (addition.op.state == ReviewerState.CC) {
         cc.addAll(addition.op.reviewers.keySet());
+        ccByEmail.addAll(addition.op.reviewersByEmail);
       }
     }
-    postReviewers.emailReviewers(change, to, cc, notify, accountsToNotify);
+    postReviewers.emailReviewers(change, to, cc, toByEmail, ccByEmail, notify, accountsToNotify);
   }
 
   private RevisionResource onBehalfOf(RevisionResource rev, ReviewInput in)

gerrit-server/src/main/java/com/google/gerrit/server/change/PostReviewers.java

@@ -23,6 +23,7 @@ import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Lists;
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.common.data.GroupDescription;
 import com.google.gerrit.common.errors.NoSuchGroupException;
@@ -32,6 +33,7 @@ import com.google.gerrit.extensions.api.changes.NotifyHandling;
 import com.google.gerrit.extensions.api.changes.RecipientType;
 import com.google.gerrit.extensions.api.changes.ReviewerInfo;
 import com.google.gerrit.extensions.client.ReviewerState;
+import com.google.gerrit.extensions.common.AccountInfo;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestModifyView;
@@ -42,6 +44,7 @@ import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.AnonymousUser;
 import com.google.gerrit.server.ApprovalsUtil;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
@@ -52,12 +55,17 @@ import com.google.gerrit.server.account.AccountsCollection;
 import com.google.gerrit.server.account.GroupMembers;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.extensions.events.ReviewerAdded;
+import com.google.gerrit.server.git.ProjectConfig;
 import com.google.gerrit.server.group.GroupsCollection;
 import com.google.gerrit.server.group.SystemGroupBackend;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.mail.send.AddReviewerSender;
+import com.google.gerrit.server.mail.send.OutgoingEmailValidator;
 import com.google.gerrit.server.notedb.NotesMigration;
+import com.google.gerrit.server.notedb.ReviewerStateInternal;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.NoSuchProjectException;
+import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.update.BatchUpdate;
 import com.google.gerrit.server.update.BatchUpdateOp;
 import com.google.gerrit.server.update.ChangeContext;
@@ -104,6 +112,8 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
   private final NotesMigration migration;
   private final AccountCache accountCache;
   private final NotifyUtil notifyUtil;
+  private final ProjectCache projectCache;
+  private final Provider<AnonymousUser> anonymousProvider;
 
   @Inject
   PostReviewers(
@@ -124,7 +134,9 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
       ReviewerAdded reviewerAdded,
       NotesMigration migration,
       AccountCache accountCache,
-      NotifyUtil notifyUtil) {
+      NotifyUtil notifyUtil,
+      ProjectCache projectCache,
+      Provider<AnonymousUser> anonymousProvider) {
     this.accounts = accounts;
     this.reviewerFactory = reviewerFactory;
     this.approvalsUtil = approvalsUtil;
@@ -143,6 +155,8 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     this.migration = migration;
     this.accountCache = accountCache;
     this.notifyUtil = notifyUtil;
+    this.projectCache = projectCache;
+    this.anonymousProvider = anonymousProvider;
   }
 
   @Override
@@ -167,6 +181,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     return addition.result;
   }
 
+  // TODO(hiesel) Refactor this as it starts to become unreadable
   public Addition prepareApplication(
       ChangeResource rsrc, AddReviewerInput input, boolean allowGroup)
       throws OrmException, RestApiException, IOException {
@@ -174,18 +189,29 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     try {
       accountId = accounts.parse(input.reviewer).getAccountId();
     } catch (UnprocessableEntityException e) {
+      ProjectConfig projectConfig = projectCache.checkedGet(rsrc.getProject()).getConfig();
       if (allowGroup) {
         try {
           return putGroup(rsrc, input);
         } catch (UnprocessableEntityException e2) {
+          if (!projectConfig.getEnableReviewerByEmail()) {
             throw new UnprocessableEntityException(
                 MessageFormat.format(
                     ChangeMessages.get().reviewerNotFoundUserOrGroup, input.reviewer));
           }
         }
+      }
+      if (!projectConfig.getEnableReviewerByEmail()) {
         throw new UnprocessableEntityException(
             MessageFormat.format(ChangeMessages.get().reviewerNotFoundUser, input.reviewer));
       }
+      return putAccountByEmail(
+          input.reviewer,
+          rsrc,
+          input.state(),
+          input.notify,
+          notifyUtil.resolveAccounts(input.notifyDetails));
+    }
     return putAccount(
         input.reviewer,
         reviewerFactory.create(rsrc, accountId),
@@ -199,6 +225,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
         user.getUserName(),
         revision.getChangeResource(),
         ImmutableMap.of(user.getAccountId(), revision.getControl()),
+        null,
         CC,
         NotifyHandling.NONE,
         ImmutableListMultimap.of());
@@ -218,6 +245,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
           reviewer,
           rsrc.getChangeResource(),
           ImmutableMap.of(member.getId(), control),
+          null,
           state,
           notify,
           accountsToNotify);
@@ -228,6 +256,32 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     throw new UnprocessableEntityException(String.format("Account of %s is inactive.", reviewer));
   }
 
+  private Addition putAccountByEmail(
+      String reviewer,
+      ChangeResource rsrc,
+      ReviewerState state,
+      NotifyHandling notify,
+      ListMultimap<RecipientType, Account.Id> accountsToNotify)
+      throws UnprocessableEntityException, OrmException, BadRequestException {
+    if (!rsrc.getControl().forUser(anonymousProvider.get()).isVisible(dbProvider.get())) {
+      throw new BadRequestException("change is not publicly visible");
+    }
+    if (!migration.readChanges()) {
+      throw new BadRequestException("feature only supported in NoteDb");
+    }
+    Address adr;
+    try {
+      adr = Address.parse(reviewer);
+    } catch (IllegalArgumentException e) {
+      throw new UnprocessableEntityException(String.format("email invalid %s", reviewer));
+    }
+    if (!OutgoingEmailValidator.isValid(adr.getEmail())) {
+      throw new UnprocessableEntityException(String.format("email invalid %s", reviewer));
+    }
+    return new Addition(
+        reviewer, rsrc, null, ImmutableList.of(adr), state, notify, accountsToNotify);
+  }
+
   private Addition putGroup(ChangeResource rsrc, AddReviewerInput input)
       throws RestApiException, OrmException, IOException {
     GroupDescription.Basic group = groupsCollection.parseInternal(input.reviewer);
@@ -283,6 +337,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
         input.reviewer,
         rsrc,
         reviewers,
+        null,
         input.state(),
         input.notify,
         notifyUtil.resolveAccounts(input.notifyDetails));
@@ -314,26 +369,28 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     final Op op;
 
     private final Map<Account.Id, ChangeControl> reviewers;
+    private final Collection<Address> reviewersByEmail;
 
     protected Addition(String reviewer) {
-      this(reviewer, null, null, REVIEWER, null, ImmutableListMultimap.of());
+      this(reviewer, null, null, null, REVIEWER, null, ImmutableListMultimap.of());
     }
 
     protected Addition(
         String reviewer,
         ChangeResource rsrc,
-        Map<Account.Id, ChangeControl> reviewers,
+        @Nullable Map<Account.Id, ChangeControl> reviewers,
+        @Nullable Collection<Address> reviewersByEmail,
         ReviewerState state,
         NotifyHandling notify,
         ListMultimap<RecipientType, Account.Id> accountsToNotify) {
       result = new AddReviewerResult(reviewer);
-      if (reviewers == null) {
+      this.reviewers = reviewers == null ? ImmutableMap.of() : reviewers;
-        this.reviewers = ImmutableMap.of();
+      this.reviewersByEmail = reviewersByEmail == null ? ImmutableList.of() : reviewersByEmail;
+      if (reviewers == null && reviewersByEmail == null) {
         op = null;
         return;
       }
-      this.reviewers = reviewers;
+      op = new Op(rsrc, this.reviewers, this.reviewersByEmail, state, notify, accountsToNotify);
-      op = new Op(rsrc, reviewers, state, notify, accountsToNotify);
     }
 
     void gatherResults() throws OrmException {
@@ -345,6 +402,9 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
           result.ccs.add(json.format(new ReviewerInfo(accountId.get()), reviewers.get(accountId)));
         }
         accountLoaderFactory.create(true).fill(result.ccs);
+        for (Address a : reviewersByEmail) {
+          result.ccs.add(new AccountInfo(a.getName(), a.getEmail()));
+        }
       } else {
         result.reviewers = Lists.newArrayListWithCapacity(op.addedReviewers.size());
         for (PatchSetApproval psa : op.addedReviewers) {
@@ -356,17 +416,22 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
                   ImmutableList.of(psa)));
         }
         accountLoaderFactory.create(true).fill(result.reviewers);
+        for (Address a : reviewersByEmail) {
+          result.reviewers.add(ReviewerInfo.byEmail(a.getName(), a.getEmail()));
+        }
       }
     }
   }
 
   public class Op implements BatchUpdateOp {
     final Map<Account.Id, ChangeControl> reviewers;
+    final Collection<Address> reviewersByEmail;
     final ReviewerState state;
     final NotifyHandling notify;
     final ListMultimap<RecipientType, Account.Id> accountsToNotify;
-    List<PatchSetApproval> addedReviewers;
+    List<PatchSetApproval> addedReviewers = new ArrayList<>();
-    Collection<Account.Id> addedCCs;
+    Collection<Account.Id> addedCCs = new ArrayList<>();
+    Collection<Address> addedCCsByEmail = new ArrayList<>();
 
     private final ChangeResource rsrc;
     private PatchSet patchSet;
@@ -374,11 +439,13 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     Op(
         ChangeResource rsrc,
         Map<Account.Id, ChangeControl> reviewers,
+        Collection<Address> reviewersByEmail,
         ReviewerState state,
         NotifyHandling notify,
         ListMultimap<RecipientType, Account.Id> accountsToNotify) {
       this.rsrc = rsrc;
       this.reviewers = reviewers;
+      this.reviewersByEmail = reviewersByEmail;
       this.state = state;
       this.notify = notify;
       this.accountsToNotify = checkNotNull(accountsToNotify);
@@ -387,6 +454,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
     @Override
     public boolean updateChange(ChangeContext ctx)
         throws RestApiException, OrmException, IOException {
+      if (!reviewers.isEmpty()) {
         if (migration.readChanges() && state == CC) {
           addedCCs =
               approvalsUtil.addCcs(
@@ -409,6 +477,12 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
             return false;
           }
         }
+      }
+
+      for (Address a : reviewersByEmail) {
+        ctx.getUpdate(ctx.getChange().currentPatchSetId())
+            .putReviewerByEmail(a, ReviewerStateInternal.fromReviewerState(state));
+      }
 
       patchSet = psUtil.current(dbProvider.get(), rsrc.getNotes());
       return true;
@@ -416,26 +490,19 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
 
     @Override
     public void postUpdate(Context ctx) throws Exception {
-      if (addedReviewers != null || addedCCs != null) {
-        if (addedReviewers == null) {
-          addedReviewers = new ArrayList<>();
-        }
-        if (addedCCs == null) {
-          addedCCs = new ArrayList<>();
-        }
       emailReviewers(
           rsrc.getChange(),
           Lists.transform(addedReviewers, r -> r.getAccountId()),
-            addedCCs,
+          addedCCs == null ? ImmutableList.of() : addedCCs,
+          reviewersByEmail,
+          addedCCsByEmail,
           notify,
           accountsToNotify);
       if (!addedReviewers.isEmpty()) {
         List<Account> reviewers =
             Lists.transform(
                 addedReviewers, psa -> accountCache.get(psa.getAccountId()).getAccount());
-          reviewerAdded.fire(
+        reviewerAdded.fire(rsrc.getChange(), patchSet, reviewers, ctx.getAccount(), ctx.getWhen());
-              rsrc.getChange(), patchSet, reviewers, ctx.getAccount(), ctx.getWhen());
-        }
       }
     }
   }
@@ -444,9 +511,11 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
       Change change,
       Collection<Account.Id> added,
       Collection<Account.Id> copied,
+      Collection<Address> addedByEmail,
+      Collection<Address> copiedByEmail,
       NotifyHandling notify,
       ListMultimap<RecipientType, Account.Id> accountsToNotify) {
-    if (added.isEmpty() && copied.isEmpty()) {
+    if (added.isEmpty() && copied.isEmpty() && addedByEmail.isEmpty() && copiedByEmail.isEmpty()) {
       return;
     }
 
@@ -466,7 +535,7 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
         toCopy.add(id);
       }
     }
-    if (toMail.isEmpty() && toCopy.isEmpty()) {
+    if (toMail.isEmpty() && toCopy.isEmpty() && addedByEmail.isEmpty() && copiedByEmail.isEmpty()) {
       return;
     }
 
@@ -478,7 +547,9 @@ public class PostReviewers implements RestModifyView<ChangeResource, AddReviewer
       cm.setAccountsToNotify(accountsToNotify);
       cm.setFrom(userId);
       cm.addReviewers(toMail);
+      cm.addReviewersByEmail(addedByEmail);
       cm.addExtraCC(toCopy);
+      cm.addExtraCCByEmail(copiedByEmail);
       cm.send();
     } catch (Exception err) {
       log.error("Cannot send email to new reviewers of change " + change.getId(), err);

gerrit-server/src/main/java/com/google/gerrit/server/change/ReviewerResource.java

@@ -14,11 +14,15 @@
 
 package com.google.gerrit.server.change;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.gerrit.common.Nullable;
 import com.google.gerrit.extensions.restapi.RestResource;
 import com.google.gerrit.extensions.restapi.RestView;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.inject.TypeLiteral;
 import com.google.inject.assistedinject.Assisted;
@@ -36,7 +40,8 @@ public class ReviewerResource implements RestResource {
 
   private final ChangeResource change;
   private final RevisionResource revision;
-  private final IdentifiedUser user;
+  @Nullable private final IdentifiedUser user;
+  @Nullable private final Address address;
 
   @AssistedInject
   ReviewerResource(
@@ -44,8 +49,9 @@ public class ReviewerResource implements RestResource {
       @Assisted ChangeResource change,
       @Assisted Account.Id id) {
     this.change = change;
-    this.revision = null;
     this.user = userFactory.create(id);
+    this.revision = null;
+    this.address = null;
   }
 
   @AssistedInject
@@ -56,6 +62,21 @@ public class ReviewerResource implements RestResource {
     this.revision = revision;
     this.change = revision.getChangeResource();
     this.user = userFactory.create(id);
+    this.address = null;
+  }
+
+  ReviewerResource(ChangeResource change, Address address) {
+    this.change = change;
+    this.address = address;
+    this.revision = null;
+    this.user = null;
+  }
+
+  ReviewerResource(RevisionResource revision, Address address) {
+    this.revision = revision;
+    this.change = revision.getChangeResource();
+    this.address = address;
+    this.user = null;
   }
 
   public ChangeResource getChangeResource() {
@@ -75,10 +96,28 @@ public class ReviewerResource implements RestResource {
   }
 
   public IdentifiedUser getReviewerUser() {
+    checkArgument(user != null, "no user provided");
     return user;
   }
 
+  public Address getReviewerByEmail() {
+    checkArgument(address != null, "no address provided");
+    return address;
+  }
+
   /**
+   * Check if this resource was constructed by email or by {@code Account.Id}.
+   *
+   * @return true if the resource was constructed by providing an {@code Address}; false if the
+   *     resource was constructed by providing an {@code Account.Id}.
+   */
+  public boolean isByEmail() {
+    return user == null;
+  }
+
+  /**
+   * Get the control for the caller's user.
+   *
    * @return the control for the caller's user (as opposed to the reviewer's user as returned by
    *     {@link #getReviewerControl()}).
    */
@@ -87,10 +126,13 @@ public class ReviewerResource implements RestResource {
   }
 
   /**
+   * Get the control for the reviewer's user.
+   *
    * @return the control for the reviewer's user (as opposed to the caller's user as returned by
    *     {@link #getControl()}).
    */
   public ChangeControl getReviewerControl() {
+    checkArgument(user != null, "no user provided");
     return change.getControl().forUser(user);
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/Reviewers.java

@@ -25,6 +25,7 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
 import com.google.gerrit.server.account.AccountsCollection;
+import com.google.gerrit.server.mail.Address;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -69,12 +70,26 @@ public class Reviewers implements ChildCollection<ChangeResource, ReviewerResour
   @Override
   public ReviewerResource parse(ChangeResource rsrc, IdString id)
       throws OrmException, ResourceNotFoundException, AuthException {
-    Account.Id accountId = accounts.parse(TopLevelResource.INSTANCE, id).getUser().getAccountId();
+    Address address = Address.tryParse(id.get());
 
+    Account.Id accountId = null;
+    try {
+      accountId = accounts.parse(TopLevelResource.INSTANCE, id).getUser().getAccountId();
+    } catch (ResourceNotFoundException e) {
+      if (address == null) {
+        throw e;
+      }
+    }
     // See if the id exists as a reviewer for this change
-    if (fetchAccountIds(rsrc).contains(accountId)) {
+    if (accountId != null && fetchAccountIds(rsrc).contains(accountId)) {
       return resourceFactory.create(rsrc, accountId);
     }
+
+    // See if the address exists as a reviewer on the change
+    if (address != null && rsrc.getNotes().getReviewersByEmail().all().contains(address)) {
+      return new ReviewerResource(rsrc, address);
+    }
+
     throw new ResourceNotFoundException(id);
   }
 

gerrit-server/src/main/java/com/google/gerrit/server/change/RevisionReviewers.java

@@ -26,6 +26,7 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.ApprovalsUtil;
 import com.google.gerrit.server.account.AccountsCollection;
+import com.google.gerrit.server.mail.Address;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
@@ -73,14 +74,28 @@ public class RevisionReviewers implements ChildCollection<RevisionResource, Revi
     if (!rsrc.isCurrent()) {
       throw new MethodNotAllowedException("Cannot access on non-current patch set");
     }
+    Address address = Address.tryParse(id.get());
 
-    Account.Id accountId = accounts.parse(TopLevelResource.INSTANCE, id).getUser().getAccountId();
+    Account.Id accountId = null;
-
+    try {
+      accountId = accounts.parse(TopLevelResource.INSTANCE, id).getUser().getAccountId();
+    } catch (ResourceNotFoundException e) {
+      if (address == null) {
+        throw e;
+      }
+    }
     Collection<Account.Id> reviewers =
         approvalsUtil.getReviewers(dbProvider.get(), rsrc.getNotes()).all();
+    // See if the id exists as a reviewer for this change
     if (reviewers.contains(accountId)) {
       return resourceFactory.create(rsrc, accountId);
     }
+
+    // See if the address exists as a reviewer on the change
+    if (address != null && rsrc.getNotes().getReviewersByEmail().all().contains(address)) {
+      return new ReviewerResource(rsrc, address);
+    }
+
     throw new ResourceNotFoundException(id);
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/git/ProjectConfig.java

@@ -155,6 +155,9 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
       ImmutableSet.of(
           "MaxWithBlock", "AnyWithBlock", "MaxNoBlock", "NoBlock", "NoOp", "PatchSetLock");
 
+  private static final String REVIEWER = "reviewer";
+  private static final String KEY_ENABLE_REVIEWER_BY_EMAIL = "enableByEmail";
+
   private static final String LEGACY_PERMISSION_PUSH_TAG = "pushTag";
   private static final String LEGACY_PERMISSION_PUSH_SIGNED_TAG = "pushSignedTag";
 
@@ -182,6 +185,7 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
   private boolean checkReceivedObjects;
   private Set<String> sectionsWithUnknownPermissions;
   private boolean hasLegacyPermissions;
+  private boolean enableReviewerByEmail;
 
   public static ProjectConfig read(MetaDataUpdate update)
       throws IOException, ConfigInvalidException {
@@ -435,6 +439,16 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     return checkReceivedObjects;
   }
 
+  /** @return the enableReviewerByEmail for this project, default is false. */
+  public boolean getEnableReviewerByEmail() {
+    return enableReviewerByEmail;
+  }
+
+  /** Set enableReviewerByEmail for this project, default is false. */
+  public void setEnableReviewerByEmail(boolean val) {
+    enableReviewerByEmail = val;
+  }
+
   /**
    * Check all GroupReferences use current group name, repairing stale ones.
    *
@@ -526,6 +540,7 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     mimeTypes = new ConfiguredMimeTypes(projectName.get(), rc);
     loadPluginSections(rc);
     loadReceiveSection(rc);
+    loadReviewerSection(rc);
   }
 
   private void loadAccountsSection(Config rc, Map<String, GroupReference> groupsByName) {
@@ -933,6 +948,10 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     maxObjectSizeLimit = rc.getLong(RECEIVE, null, KEY_MAX_OBJECT_SIZE_LIMIT, 0);
   }
 
+  private void loadReviewerSection(Config rc) {
+    enableReviewerByEmail = rc.getBoolean(REVIEWER, null, KEY_ENABLE_REVIEWER_BY_EMAIL, false);
+  }
+
   private void loadPluginSections(Config rc) {
     pluginConfigs = new HashMap<>();
     for (String plugin : rc.getSubsections(PLUGIN)) {
@@ -1067,6 +1086,7 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     saveAccessSections(rc, keepGroups);
     saveNotifySections(rc, keepGroups);
     savePluginSections(rc, keepGroups);
+    saveReviewerSection(rc);
     groupList.retainUUIDs(keepGroups);
     saveLabelSections(rc);
     saveSubscribeSections(rc);
@@ -1288,40 +1308,55 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
 
       setBooleanConfigKey(
           rc,
+          LABEL,
           name,
           KEY_ALLOW_POST_SUBMIT,
           label.allowPostSubmit(),
           LabelType.DEF_ALLOW_POST_SUBMIT);
       setBooleanConfigKey(
-          rc, name, KEY_COPY_MIN_SCORE, label.isCopyMinScore(), LabelType.DEF_COPY_MIN_SCORE);
+          rc,
-      setBooleanConfigKey(
+          LABEL,
-          rc, name, KEY_COPY_MAX_SCORE, label.isCopyMaxScore(), LabelType.DEF_COPY_MAX_SCORE);
+          name,
+          KEY_COPY_MIN_SCORE,
+          label.isCopyMinScore(),
+          LabelType.DEF_COPY_MIN_SCORE);
       setBooleanConfigKey(
           rc,
+          LABEL,
+          name,
+          KEY_COPY_MAX_SCORE,
+          label.isCopyMaxScore(),
+          LabelType.DEF_COPY_MAX_SCORE);
+      setBooleanConfigKey(
+          rc,
+          LABEL,
           name,
           KEY_COPY_ALL_SCORES_ON_TRIVIAL_REBASE,
           label.isCopyAllScoresOnTrivialRebase(),
           LabelType.DEF_COPY_ALL_SCORES_ON_TRIVIAL_REBASE);
       setBooleanConfigKey(
           rc,
+          LABEL,
           name,
           KEY_COPY_ALL_SCORES_IF_NO_CODE_CHANGE,
           label.isCopyAllScoresIfNoCodeChange(),
           LabelType.DEF_COPY_ALL_SCORES_IF_NO_CODE_CHANGE);
       setBooleanConfigKey(
           rc,
+          LABEL,
           name,
           KEY_COPY_ALL_SCORES_IF_NO_CHANGE,
           label.isCopyAllScoresIfNoChange(),
           LabelType.DEF_COPY_ALL_SCORES_IF_NO_CHANGE);
       setBooleanConfigKey(
           rc,
+          LABEL,
           name,
           KEY_COPY_ALL_SCORES_ON_MERGE_FIRST_PARENT_UPDATE,
           label.isCopyAllScoresOnMergeFirstParentUpdate(),
           LabelType.DEF_COPY_ALL_SCORES_ON_MERGE_FIRST_PARENT_UPDATE);
       setBooleanConfigKey(
-          rc, name, KEY_CAN_OVERRIDE, label.canOverride(), LabelType.DEF_CAN_OVERRIDE);
+          rc, LABEL, name, KEY_CAN_OVERRIDE, label.canOverride(), LabelType.DEF_CAN_OVERRIDE);
       List<String> values = Lists.newArrayListWithCapacity(label.getValues().size());
       for (LabelValue value : label.getValues()) {
         values.add(value.format());
@@ -1335,11 +1370,11 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
   }
 
   private static void setBooleanConfigKey(
-      Config rc, String name, String key, boolean value, boolean defaultValue) {
+      Config rc, String section, String name, String key, boolean value, boolean defaultValue) {
     if (value == defaultValue) {
-      rc.unset(LABEL, name, key);
+      rc.unset(section, name, key);
     } else {
-      rc.setBoolean(LABEL, name, key, value);
+      rc.setBoolean(section, name, key, value);
     }
   }
 
@@ -1367,6 +1402,11 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
     }
   }
 
+  private void saveReviewerSection(Config rc) {
+    setBooleanConfigKey(
+        rc, REVIEWER, null, KEY_ENABLE_REVIEWER_BY_EMAIL, enableReviewerByEmail, false);
+  }
+
   private void saveGroupList() throws IOException {
     saveUTF8(GroupList.FILE_NAME, groupList.asText());
   }

gerrit-server/src/main/java/com/google/gerrit/server/mail/Address.java

@@ -42,6 +42,14 @@ public class Address {
     throw new IllegalArgumentException("Invalid email address: " + in);
   }
 
+  public static Address tryParse(String in) {
+    try {
+      return parse(in);
+    } catch (IllegalArgumentException e) {
+      return null;
+    }
+  }
+
   final String name;
   final String email;
 

gerrit-server/src/main/java/com/google/gerrit/server/mail/send/ChangeEmail.java

@@ -180,6 +180,20 @@ public abstract class ChangeEmail extends NotificationEmail {
     setHeader("X-Gerrit-Change-Number", "" + change.getChangeId());
     setChangeUrlHeader();
     setCommitIdHeader();
+
+    if (notify.ordinal() >= NotifyHandling.OWNER_REVIEWERS.ordinal()) {
+      try {
+        // TODO(hiesel) Load from index instead
+        addByEmail(
+            RecipientType.CC,
+            changeData.notes().getReviewersByEmail().byState(ReviewerStateInternal.CC));
+        addByEmail(
+            RecipientType.TO,
+            changeData.notes().getReviewersByEmail().byState(ReviewerStateInternal.REVIEWER));
+      } catch (OrmException e) {
+        throw new EmailException("Failed to add unregistered CCs " + change.getChangeId(), e);
+      }
+    }
   }
 
   private void setChangeUrlHeader() {

gerrit-server/src/main/java/com/google/gerrit/server/mail/send/DeleteReviewerSender.java

@@ -20,6 +20,7 @@ import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.server.account.WatchConfig.NotifyType;
+import com.google.gerrit.server.mail.Address;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.assistedinject.Assisted;
@@ -32,6 +33,7 @@ import java.util.Set;
 /** Let users know that a reviewer and possibly her review have been removed. */
 public class DeleteReviewerSender extends ReplyToChangeSender {
   private final Set<Account.Id> reviewers = new HashSet<>();
+  private final Set<Address> reviewersByEmail = new HashSet<>();
 
   public interface Factory extends ReplyToChangeSender.Factory<DeleteReviewerSender> {
     @Override
@@ -49,6 +51,10 @@ public class DeleteReviewerSender extends ReplyToChangeSender {
     reviewers.addAll(cc);
   }
 
+  public void addReviewersByEmail(Collection<Address> cc) {
+    reviewersByEmail.addAll(cc);
+  }
+
   @Override
   protected void init() throws EmailException {
     super.init();
@@ -58,6 +64,7 @@ public class DeleteReviewerSender extends ReplyToChangeSender {
     ccExistingReviewers();
     includeWatchers(NotifyType.ALL_COMMENTS);
     add(RecipientType.TO, reviewers);
+    addByEmail(RecipientType.TO, reviewersByEmail);
     removeUsersThatIgnoredTheChange();
   }
 
@@ -70,13 +77,16 @@ public class DeleteReviewerSender extends ReplyToChangeSender {
   }
 
   public List<String> getReviewerNames() {
-    if (reviewers.isEmpty()) {
+    if (reviewers.isEmpty() && reviewersByEmail.isEmpty()) {
       return null;
     }
     List<String> names = new ArrayList<>();
     for (Account.Id id : reviewers) {
       names.add(getNameFor(id));
     }
+    for (Address a : reviewersByEmail) {
+      names.add(a.toString());
+    }
     return names;
   }
 

gerrit-server/src/main/java/com/google/gerrit/server/mail/send/NewChangeSender.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.mail.send;
 import com.google.gerrit.common.errors.EmailException;
 import com.google.gerrit.extensions.api.changes.RecipientType;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.OrmException;
 import java.util.ArrayList;
@@ -28,7 +29,9 @@ import java.util.Set;
 /** Sends an email alerting a user to a new change for them to review. */
 public abstract class NewChangeSender extends ChangeEmail {
   private final Set<Account.Id> reviewers = new HashSet<>();
+  private final Set<Address> reviewersByEmail = new HashSet<>();
   private final Set<Account.Id> extraCC = new HashSet<>();
+  private final Set<Address> extraCCByEmail = new HashSet<>();
 
   protected NewChangeSender(EmailArguments ea, ChangeData cd) throws OrmException {
     super(ea, "newchange", cd);
@@ -38,10 +41,18 @@ public abstract class NewChangeSender extends ChangeEmail {
     reviewers.addAll(cc);
   }
 
+  public void addReviewersByEmail(final Collection<Address> cc) {
+    reviewersByEmail.addAll(cc);
+  }
+
   public void addExtraCC(final Collection<Account.Id> cc) {
     extraCC.addAll(cc);
   }
 
+  public void addExtraCCByEmail(final Collection<Address> cc) {
+    extraCCByEmail.addAll(cc);
+  }
+
   @Override
   protected void init() throws EmailException {
     super.init();
@@ -55,9 +66,11 @@ public abstract class NewChangeSender extends ChangeEmail {
       case ALL:
       default:
         add(RecipientType.CC, extraCC);
+        extraCCByEmail.stream().forEach(cc -> add(RecipientType.CC, cc));
         //$FALL-THROUGH$
       case OWNER_REVIEWERS:
         add(RecipientType.TO, reviewers);
+        addByEmail(RecipientType.TO, reviewersByEmail);
         break;
     }
 

gerrit-server/src/main/java/com/google/gerrit/server/mail/send/OutgoingEmail.java

@@ -441,6 +441,13 @@ public abstract class OutgoingEmail {
     }
   }
 
+  /** Schedule this message for delivery to the listed address. */
+  protected void addByEmail(final RecipientType rt, final Collection<Address> list) {
+    for (final Address id : list) {
+      add(rt, id);
+    }
+  }
+
   protected void add(final RecipientType rt, final UserIdentity who) {
     if (who != null && who.getAccount() != null) {
       add(rt, who.getAccount());

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotes.java

@@ -48,6 +48,7 @@ import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.client.RobotComment;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.reviewdb.server.ReviewDbUtil;
+import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.git.RefCache;
@@ -428,6 +429,11 @@ public class ChangeNotes extends AbstractChangeNotes<ChangeNotes> {
     return state.reviewers();
   }
 
+  /** @return reviewers that do not currently have a Gerrit account and were added by email. */
+  public ReviewerByEmailSet getReviewersByEmail() {
+    return state.reviewersByEmail();
+  }
+
   public ImmutableList<ReviewerStatusUpdate> getReviewerUpdates() {
     return state.reviewerUpdates();
   }

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesParser.java

@@ -63,8 +63,10 @@ import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.reviewdb.client.RevId;
 import com.google.gerrit.reviewdb.server.ReviewDbUtil;
+import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
 import com.google.gerrit.server.util.LabelVote;
 import java.io.IOException;
@@ -128,6 +130,7 @@ class ChangeNotesParser {
   // Private final but mutable members initialized in the constructor and filled
   // in during the parsing process.
   private final Table<Account.Id, ReviewerStateInternal, Timestamp> reviewers;
+  private final Table<Address, ReviewerStateInternal, Timestamp> reviewersByEmail;
   private final List<Account.Id> allPastReviewers;
   private final List<ReviewerStatusUpdate> reviewerUpdates;
   private final List<SubmitRecord> submitRecords;
@@ -174,6 +177,7 @@ class ChangeNotesParser {
     approvals = new LinkedHashMap<>();
     bufferedApprovals = new ArrayList<>();
     reviewers = HashBasedTable.create();
+    reviewersByEmail = HashBasedTable.create();
     allPastReviewers = new ArrayList<>();
     reviewerUpdates = new ArrayList<>();
     submitRecords = Lists.newArrayListWithExpectedSize(1);
@@ -201,6 +205,7 @@ class ChangeNotesParser {
       parseNotes();
       allPastReviewers.addAll(reviewers.rowKeySet());
       pruneReviewers();
+      pruneReviewersByEmail();
 
       updatePatchSetStates();
       checkMandatoryFooters();
@@ -234,6 +239,7 @@ class ChangeNotesParser {
         patchSets,
         buildApprovals(),
         ReviewerSet.fromTable(Tables.transpose(reviewers)),
+        ReviewerByEmailSet.fromTable(Tables.transpose(reviewersByEmail)),
         allPastReviewers,
         buildReviewerUpdates(),
         submitRecords,
@@ -374,6 +380,9 @@ class ChangeNotesParser {
       for (String line : commit.getFooterLineValues(state.getFooterKey())) {
         parseReviewer(ts, state, line);
       }
+      for (String line : commit.getFooterLineValues(state.getByEmailFooterKey())) {
+        parseReviewerByEmail(ts, state, line);
+      }
       // Don't update timestamp when a reviewer was added, matching RevewDb
       // behavior.
     }
@@ -917,6 +926,19 @@ class ChangeNotesParser {
     }
   }
 
+  private void parseReviewerByEmail(Timestamp ts, ReviewerStateInternal state, String line)
+      throws ConfigInvalidException {
+    Address adr;
+    try {
+      adr = Address.parse(line);
+    } catch (IllegalArgumentException e) {
+      throw invalidFooter(state.getByEmailFooterKey(), line);
+    }
+    if (!reviewersByEmail.containsRow(adr)) {
+      reviewersByEmail.put(adr, state, ts);
+    }
+  }
+
   private void parseReadOnlyUntil(ChangeNotesCommit commit) throws ConfigInvalidException {
     String raw = parseOneFooter(commit, FOOTER_READ_ONLY_UNTIL);
     if (raw == null) {
@@ -956,6 +978,17 @@ class ChangeNotesParser {
     }
   }
 
+  private void pruneReviewersByEmail() {
+    Iterator<Table.Cell<Address, ReviewerStateInternal, Timestamp>> rit =
+        reviewersByEmail.cellSet().iterator();
+    while (rit.hasNext()) {
+      Table.Cell<Address, ReviewerStateInternal, Timestamp> e = rit.next();
+      if (e.getColumnKey() == ReviewerStateInternal.REMOVED) {
+        rit.remove();
+      }
+    }
+  }
+
   private void updatePatchSetStates() {
     Set<PatchSet.Id> missing = new TreeSet<>(ReviewDbUtil.intKeyOrdering());
     for (Iterator<PatchSet> it = patchSets.values().iterator(); it.hasNext(); ) {

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeNotesState.java

@@ -34,6 +34,7 @@ import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.client.RevId;
+import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.notedb.NoteDbChangeState.PrimaryStorage;
@@ -65,6 +66,7 @@ public abstract class ChangeNotesState {
         ImmutableList.of(),
         ImmutableList.of(),
         ReviewerSet.empty(),
+        ReviewerByEmailSet.empty(),
         ImmutableList.of(),
         ImmutableList.of(),
         ImmutableList.of(),
@@ -95,6 +97,7 @@ public abstract class ChangeNotesState {
       Map<PatchSet.Id, PatchSet> patchSets,
       ListMultimap<PatchSet.Id, PatchSetApproval> approvals,
       ReviewerSet reviewers,
+      ReviewerByEmailSet reviewersByEmail,
       List<Account.Id> allPastReviewers,
       List<ReviewerStatusUpdate> reviewerUpdates,
       List<SubmitRecord> submitRecords,
@@ -128,6 +131,7 @@ public abstract class ChangeNotesState {
         ImmutableList.copyOf(patchSets.entrySet()),
         ImmutableList.copyOf(approvals.entries()),
         reviewers,
+        reviewersByEmail,
         ImmutableList.copyOf(allPastReviewers),
         ImmutableList.copyOf(reviewerUpdates),
         ImmutableList.copyOf(submitRecords),
@@ -204,6 +208,8 @@ public abstract class ChangeNotesState {
 
   abstract ReviewerSet reviewers();
 
+  abstract ReviewerByEmailSet reviewersByEmail();
+
   abstract ImmutableList<Account.Id> allPastReviewers();
 
   abstract ImmutableList<ReviewerStatusUpdate> reviewerUpdates();

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ChangeUpdate.java

@@ -61,6 +61,7 @@ import com.google.gerrit.server.GerritPersonIdent;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.config.AnonymousCowardName;
 import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.project.ChangeControl;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.util.LabelVote;
@@ -128,6 +129,7 @@ public class ChangeUpdate extends AbstractChangeUpdate {
 
   private final Table<String, Account.Id, Optional<Short>> approvals;
   private final Map<Account.Id, ReviewerStateInternal> reviewers = new LinkedHashMap<>();
+  private final Map<Address, ReviewerStateInternal> reviewersByEmail = new LinkedHashMap<>();
   private final List<Comment> comments = new ArrayList<>();
 
   private String commitSubject;
@@ -471,6 +473,15 @@ public class ChangeUpdate extends AbstractChangeUpdate {
     reviewers.put(reviewer, ReviewerStateInternal.REMOVED);
   }
 
+  public void putReviewerByEmail(Address reviewer, ReviewerStateInternal type) {
+    checkArgument(type != ReviewerStateInternal.REMOVED, "invalid ReviewerType");
+    reviewersByEmail.put(reviewer, type);
+  }
+
+  public void removeReviewerByEmail(Address reviewer) {
+    reviewersByEmail.put(reviewer, ReviewerStateInternal.REMOVED);
+  }
+
   public void setPatchSetState(PatchSetState psState) {
     this.psState = psState;
   }
@@ -660,6 +671,10 @@ public class ChangeUpdate extends AbstractChangeUpdate {
       addIdent(msg, e.getKey()).append('\n');
     }
 
+    for (Map.Entry<Address, ReviewerStateInternal> e : reviewersByEmail.entrySet()) {
+      addFooter(msg, e.getValue().getByEmailFooterKey(), e.getKey().toString());
+    }
+
     for (Table.Cell<String, Account.Id, Optional<Short>> c : approvals.cellSet()) {
       addFooter(msg, FOOTER_LABEL);
       // Label names/values are safe to append without sanitizing.
@@ -749,6 +764,7 @@ public class ChangeUpdate extends AbstractChangeUpdate {
         && changeMessage == null
         && comments.isEmpty()
         && reviewers.isEmpty()
+        && reviewersByEmail.isEmpty()
         && changeId == null
         && branch == null
         && status == null

gerrit-server/src/main/java/com/google/gerrit/server/notedb/ReviewerStateInternal.java

@@ -29,13 +29,17 @@ public enum ReviewerStateInternal {
   /** The user was previously a reviewer on the change, but was removed. */
   REMOVED(new FooterKey("Removed"), ReviewerState.REMOVED);
 
+  public static ReviewerStateInternal fromReviewerState(ReviewerState state) {
+    return ReviewerStateInternal.values()[state.ordinal()];
+  }
+
   static {
     boolean ok = true;
     if (ReviewerStateInternal.values().length != ReviewerState.values().length) {
       ok = false;
     }
-    for (ReviewerStateInternal s : ReviewerStateInternal.values()) {
+    for (int i = 0; i < ReviewerStateInternal.values().length; i++) {
-      ok &= s.name().equals(s.state.name());
+      ok &= ReviewerState.values()[i].equals(ReviewerStateInternal.values()[i].state);
     }
     if (!ok) {
       throw new IllegalStateException(
@@ -58,6 +62,10 @@ public enum ReviewerStateInternal {
     return footerKey;
   }
 
+  FooterKey getByEmailFooterKey() {
+    return new FooterKey(footerKey.getName() + "-email");
+  }
+
   public ReviewerState asReviewerState() {
     return state;
   }

gerrit-server/src/main/java/com/google/gerrit/server/project/ConfigInfoImpl.java

@@ -58,6 +58,7 @@ public class ConfigInfoImpl extends ConfigInfo {
     InheritedBooleanInfo enableSignedPush = new InheritedBooleanInfo();
     InheritedBooleanInfo requireSignedPush = new InheritedBooleanInfo();
     InheritedBooleanInfo rejectImplicitMerges = new InheritedBooleanInfo();
+    InheritedBooleanInfo enableReviewerByEmail = new InheritedBooleanInfo();
 
     useContributorAgreements.value = projectState.isUseContributorAgreements();
     useSignedOffBy.value = projectState.isUseSignedOffBy();
@@ -73,6 +74,7 @@ public class ConfigInfoImpl extends ConfigInfo {
     enableSignedPush.configuredValue = p.getEnableSignedPush();
     requireSignedPush.configuredValue = p.getRequireSignedPush();
     rejectImplicitMerges.configuredValue = p.getRejectImplicitMerges();
+    enableReviewerByEmail.configuredValue = p.getEnableReviewerByEmail();
 
     ProjectState parentState = Iterables.getFirst(projectState.parents(), null);
     if (parentState != null) {
@@ -85,6 +87,7 @@ public class ConfigInfoImpl extends ConfigInfo {
       enableSignedPush.inheritedValue = projectState.isEnableSignedPush();
       requireSignedPush.inheritedValue = projectState.isRequireSignedPush();
       rejectImplicitMerges.inheritedValue = projectState.isRejectImplicitMerges();
+      enableReviewerByEmail.inheritedValue = projectState.isEnableReviewerByEmail();
     }
 
     this.useContributorAgreements = useContributorAgreements;

gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectState.java

@@ -394,6 +394,10 @@ public class ProjectState {
     return getInheritableBoolean(Project::getRejectImplicitMerges);
   }
 
+  public boolean isEnableReviewerByEmail() {
+    return getInheritableBoolean(Project::getEnableReviewerByEmail);
+  }
+
   public LabelTypes getLabelTypes() {
     Map<String, LabelType> types = new LinkedHashMap<>();
     for (ProjectState s : treeInOrder()) {

gerrit-server/src/test/java/com/google/gerrit/server/git/ProjectConfigTest.java

@@ -105,7 +105,9 @@ public class ProjectConfigTest extends LocalDiskRepositoryTestCase {
                             + "  accepted = group Developers\n" //
                             + "  accepted = group Staff\n" //
                             + "  autoVerify = group Developers\n" //
-                            + "  agreementUrl = http://www.example.com/agree\n")) //
+                            + "  agreementUrl = http://www.example.com/agree\n" //
+                            + "[reviewer]\n" //
+                            + "  enableByEmail = true\n")) //
                 ));
 
     ProjectConfig cfg = read(rev);
@@ -132,6 +134,8 @@ public class ProjectConfigTest extends LocalDiskRepositoryTestCase {
     assertThat(submit.getExclusiveGroup()).isTrue();
     assertThat(read.getExclusiveGroup()).isTrue();
     assertThat(push.getExclusiveGroup()).isFalse();
+
+    assertThat(cfg.getEnableReviewerByEmail()).isTrue();
   }
 
   @Test

gerrit-server/src/test/java/com/google/gerrit/server/notedb/ChangeNotesTest.java

@@ -49,6 +49,7 @@ import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.config.GerritServerId;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
 import com.google.gerrit.server.util.RequestId;
 import com.google.gerrit.testutil.TestChanges;
@@ -3298,6 +3299,105 @@ public class ChangeNotesTest extends AbstractChangeNotesTest {
     assertThat(notes.isPrivate()).isFalse();
   }
 
+  @Test
+  public void defaultReviewersByEmailIsEmpty() throws Exception {
+    Change c = newChange();
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().all()).isEmpty();
+  }
+
+  @Test
+  public void putReviewerByEmail() throws Exception {
+    Address adr = new Address("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().all()).containsExactly(adr);
+  }
+
+  @Test
+  public void putAndRemoveReviewerByEmail() throws Exception {
+    Address adr = new Address("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    update = newUpdate(c, changeOwner);
+    update.removeReviewerByEmail(adr);
+    update.commit();
+
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().all()).isEmpty();
+  }
+
+  @Test
+  public void putRemoveAndAddBackReviewerByEmail() throws Exception {
+    Address adr = new Address("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    update = newUpdate(c, changeOwner);
+    update.removeReviewerByEmail(adr);
+    update.commit();
+
+    update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.CC);
+    update.commit();
+
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().all()).containsExactly(adr);
+  }
+
+  @Test
+  public void putReviewerByEmailAndCcByEmail() throws Exception {
+    Address adrReviewer = new Address("Foo Bar", "foo.bar@gerritcodereview.com");
+    Address adrCc = new Address("Foo Bor", "foo.bar.2@gerritcodereview.com");
+
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adrReviewer, ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adrCc, ReviewerStateInternal.CC);
+    update.commit();
+
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().byState(ReviewerStateInternal.REVIEWER))
+        .containsExactly(adrReviewer);
+    assertThat(notes.getReviewersByEmail().byState(ReviewerStateInternal.CC))
+        .containsExactly(adrCc);
+    assertThat(notes.getReviewersByEmail().all()).containsExactly(adrReviewer, adrCc);
+  }
+
+  @Test
+  public void putReviewerByEmailAndChangeToCc() throws Exception {
+    Address adr = new Address("Foo Bar", "foo.bar@gerritcodereview.com");
+
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(adr, ReviewerStateInternal.CC);
+    update.commit();
+
+    ChangeNotes notes = newNotes(c);
+    assertThat(notes.getReviewersByEmail().byState(ReviewerStateInternal.REVIEWER)).isEmpty();
+    assertThat(notes.getReviewersByEmail().byState(ReviewerStateInternal.CC)).containsExactly(adr);
+    assertThat(notes.getReviewersByEmail().all()).containsExactly(adr);
+  }
+
   private boolean testJson() {
     return noteUtil.getWriteJson();
   }

gerrit-server/src/test/java/com/google/gerrit/server/notedb/CommitMessageOutputTest.java

@@ -23,6 +23,7 @@ import com.google.gerrit.common.TimeUtil;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.mail.Address;
 import com.google.gerrit.server.util.RequestId;
 import com.google.gerrit.testutil.ConfigSuite;
 import com.google.gerrit.testutil.TestChanges;
@@ -382,6 +383,32 @@ public class CommitMessageOutputTest extends AbstractChangeNotesTest {
     assertBodyEquals("Update patch set 1\n\nPatch-set: 1\nCurrent: true\n", update.getResult());
   }
 
+  @Test
+  public void reviewerByEmail() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(
+        new Address("John Doe", "j.doe@gerritcodereview.com"), ReviewerStateInternal.REVIEWER);
+    update.commit();
+
+    assertBodyEquals(
+        "Update patch set 1\n\nPatch-set: 1\n"
+            + "Reviewer-email: John Doe <j.doe@gerritcodereview.com>\n",
+        update.getResult());
+  }
+
+  @Test
+  public void ccByEmail() throws Exception {
+    Change c = newChange();
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.putReviewerByEmail(new Address("j.doe@gerritcodereview.com"), ReviewerStateInternal.CC);
+    update.commit();
+
+    assertBodyEquals(
+        "Update patch set 1\n\nPatch-set: 1\nCC-email: j.doe@gerritcodereview.com\n",
+        update.getResult());
+  }
+
   private RevCommit parseCommit(ObjectId id) throws Exception {
     if (id instanceof RevCommit) {
       return (RevCommit) id;