Disable capability endpoints when not using default backend

The capability names exposed by these endpoints are implementation
details of the DefaultPermissionBackend. A different implementation may
choose to hide the GlobalPermission enum names from the user entirely,
so it doesn't make sense to expose them.

Change-Id: I69ea38064ccbf1c04a976e7bcb4629ab5d66aeef

java/com/google/gerrit/server/permissions/DefaultPermissionBackend.java

@@ -84,6 +84,11 @@ public class DefaultPermissionBackend extends PermissionBackend {
     return new WithUserImpl(identifiedUser);
   }
 
+  @Override
+  public boolean usesDefaultCapabilities() {
+    return true;
+  }
+
   class WithUserImpl extends WithUser {
     private final CurrentUser user;
     private Boolean admin;

java/com/google/gerrit/server/permissions/PermissionBackend.java

@@ -23,6 +23,7 @@ import com.google.gerrit.common.data.LabelType;
 import com.google.gerrit.extensions.api.access.GlobalOrPluginPermission;
 import com.google.gerrit.extensions.conditions.BooleanCondition;
 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.Branch;
 import com.google.gerrit.reviewdb.client.Project;
@@ -112,6 +113,29 @@ public abstract class PermissionBackend {
    */
   public abstract WithUser absentUser(Account.Id user);
 
+  /**
+   * Check whether this {@code PermissionBackend} respects the same global capabilities as the
+   * {@link DefaultPermissionBackend}.
+   *
+   * <p>If true, then it makes sense for downstream callers to refer to built-in Gerrit capability
+   * names in user-facing error messages, for example.
+   *
+   * @return whether this is the default permission backend.
+   */
+  public boolean usesDefaultCapabilities() {
+    return false;
+  }
+
+  /**
+   * Throw {@link ResourceNotFoundException} if this backend does not use the default global
+   * capabilities.
+   */
+  public void checkUsesDefaultCapabilities() throws ResourceNotFoundException {
+    if (!usesDefaultCapabilities()) {
+      throw new ResourceNotFoundException("Gerrit capabilities not used on this server");
+    }
+  }
+
   /**
    * Bulk evaluate a set of {@link PermissionBackendCondition} for view handling.
    *

java/com/google/gerrit/server/restapi/account/Capabilities.java

@@ -60,6 +60,7 @@ class Capabilities implements ChildCollection<AccountResource, AccountResource.C
   @Override
   public Capability parse(AccountResource parent, IdString id)
       throws ResourceNotFoundException, AuthException, PermissionBackendException {
+    permissionBackend.checkUsesDefaultCapabilities();
     IdentifiedUser target = parent.getUser();
     if (self.get() != target) {
       permissionBackend.currentUser().check(GlobalPermission.ADMINISTRATE_SERVER);

java/com/google/gerrit/server/restapi/account/GetCapabilities.java

@@ -23,8 +23,9 @@ import com.google.gerrit.extensions.api.access.GlobalOrPluginPermission;
 import com.google.gerrit.extensions.api.access.PluginPermission;
 import com.google.gerrit.extensions.config.CapabilityDefinition;
 import com.google.gerrit.extensions.registration.DynamicMap;
-import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BinaryResult;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
+import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.OptionUtil;
@@ -75,7 +76,8 @@ class GetCapabilities implements RestReadView<AccountResource> {
   }
 
   @Override
-  public Object apply(AccountResource rsrc) throws AuthException, PermissionBackendException {
+  public Object apply(AccountResource rsrc) throws RestApiException, PermissionBackendException {
+    permissionBackend.checkUsesDefaultCapabilities();
     PermissionBackend.WithUser perm = permissionBackend.currentUser();
     if (self.get() != rsrc.getUser()) {
       perm.check(GlobalPermission.ADMINISTRATE_SERVER);
@@ -158,8 +160,16 @@ class GetCapabilities implements RestReadView<AccountResource> {
 
   @Singleton
   static class CheckOne implements RestReadView<AccountResource.Capability> {
+    private final PermissionBackend permissionBackend;
+
+    @Inject
+    CheckOne(PermissionBackend permissionBackend) {
+      this.permissionBackend = permissionBackend;
+    }
+
     @Override
-    public BinaryResult apply(Capability resource) {
+    public BinaryResult apply(Capability resource) throws ResourceNotFoundException {
+      permissionBackend.checkUsesDefaultCapabilities();
       return BinaryResult.create("ok\n");
     }
   }

java/com/google/gerrit/server/restapi/config/ListCapabilities.java

@@ -18,9 +18,11 @@ import com.google.common.collect.ImmutableMap;
 import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.extensions.config.CapabilityDefinition;
 import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.server.config.CapabilityConstants;
 import com.google.gerrit.server.config.ConfigResource;
+import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
@@ -36,16 +38,20 @@ public class ListCapabilities implements RestReadView<ConfigResource> {
   private static final Logger log = LoggerFactory.getLogger(ListCapabilities.class);
   private static final Pattern PLUGIN_NAME_PATTERN = Pattern.compile("^[a-zA-Z0-9-]+$");
 
+  private final PermissionBackend permissionBackend;
   private final DynamicMap<CapabilityDefinition> pluginCapabilities;
 
   @Inject
-  public ListCapabilities(DynamicMap<CapabilityDefinition> pluginCapabilities) {
+  public ListCapabilities(
+      PermissionBackend permissionBackend, DynamicMap<CapabilityDefinition> pluginCapabilities) {
+    this.permissionBackend = permissionBackend;
     this.pluginCapabilities = pluginCapabilities;
   }
 
   @Override
   public Map<String, CapabilityInfo> apply(ConfigResource resource)
-      throws IllegalAccessException, NoSuchFieldException {
+      throws ResourceNotFoundException, IllegalAccessException, NoSuchFieldException {
+    permissionBackend.checkUsesDefaultCapabilities();
     return ImmutableMap.<String, CapabilityInfo>builder()
         .putAll(collectCoreCapabilities())
         .putAll(collectPluginCapabilities())

javatests/com/google/gerrit/server/config/ListCapabilitiesTest.java

@@ -20,11 +20,15 @@ import com.google.gerrit.common.data.GlobalCapability;
 import com.google.gerrit.extensions.annotations.Exports;
 import com.google.gerrit.extensions.config.CapabilityDefinition;
 import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.reviewdb.client.Account.Id;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.permissions.PermissionBackend;
 import com.google.gerrit.server.restapi.config.ListCapabilities;
 import com.google.gerrit.server.restapi.config.ListCapabilities.CapabilityInfo;
 import com.google.inject.AbstractModule;
 import com.google.inject.Guice;
 import com.google.inject.Injector;
+import com.google.inject.Singleton;
 import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
@@ -48,6 +52,7 @@ public class ListCapabilitiesTest {
                         return "Print Hello";
                       }
                     });
+            bind(PermissionBackend.class).to(FakePermissionBackend.class);
           }
         };
     injector = Guice.createInjector(mod);
@@ -68,4 +73,27 @@ public class ListCapabilitiesTest {
     assertThat(m.get(pluginCapability).id).isEqualTo(pluginCapability);
     assertThat(m.get(pluginCapability).name).isEqualTo("Print Hello");
   }
+
+  @Singleton
+  private static class FakePermissionBackend extends PermissionBackend {
+    @Override
+    public WithUser currentUser() {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public WithUser user(CurrentUser user) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public WithUser absentUser(Id user) {
+      throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean usesDefaultCapabilities() {
+      return true;
+    }
+  }
 }