ChangeScreen2: Make diff against revision persistent

2d2a3c405e added diff against to the change
screen2. However base revision is lost when side by side view is closed.

This change fixes that.

Conflicts:
	gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.java

Change-Id: I7f74760fde96469a60556f657923a3936d6516c7

gerrit-gwtui/src/main/java/com/google/gerrit/client/Dispatcher.java

@@ -482,7 +482,7 @@ public class Dispatcher {
     if (rest.isEmpty()) {
       Gerrit.display(token, panel== null
           ? (isChangeScreen2()
-              ? new ChangeScreen2(id, null, false)
+              ? new ChangeScreen2(id, null, null, false)
               : new ChangeScreen(id))
           : new NotFoundScreen());
       return;
@@ -515,7 +515,11 @@ public class Dispatcher {
     } else {
       if (panel == null) {
         Gerrit.display(token, isChangeScreen2()
-            ? new ChangeScreen2(id, String.valueOf(ps.get()), false)
+            ? new ChangeScreen2(id,
+                base != null
+                    ? String.valueOf(base.get())
+                    : null,
+                String.valueOf(ps.get()), false)
             : new ChangeScreen(id));
       } else if ("publish".equals(panel)) {
         publish(ps);

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.java

@@ -116,6 +116,7 @@ public class ChangeScreen2 extends Screen {
   }
 
   private final Change.Id changeId;
+  private String base;
   private String revision;
   private ChangeInfo changeInfo;
   private CommentLinkProcessor commentLinkProcessor;
@@ -172,9 +173,10 @@ public class ChangeScreen2 extends Screen {
   private RevisionsAction revisionsAction;
   private DownloadAction downloadAction;
 
-  public ChangeScreen2(Change.Id changeId, String revision, boolean openReplyBox) {
+  public ChangeScreen2(Change.Id changeId, String base, String revision, boolean openReplyBox) {
     this.changeId = changeId;
-    this.revision = revision != null && !revision.isEmpty() ? revision : null;
+    this.base = normalize(base);
+    this.revision = normalize(revision);
     this.openReplyBox = openReplyBox;
     add(uiBinder.createAndBindUi(this));
   }
@@ -190,7 +192,7 @@ public class ChangeScreen2 extends Screen {
       @Override
       public void onSuccess(ChangeInfo info) {
         info.init();
-        loadConfigInfo(info, null);
+        loadConfigInfo(info, base);
       }
     });
   }
@@ -459,9 +461,10 @@ public class ChangeScreen2 extends Screen {
   private void loadConfigInfo(final ChangeInfo info, final String base) {
     info.revisions().copyKeysIntoChildren("name");
     final RevisionInfo rev = resolveRevisionToDisplay(info);
+    final RevisionInfo b = resolveRevisionOrPatchSetId(info, base, null);
 
     CallbackGroup group = new CallbackGroup();
-    loadDiff(info.revisions().get(base), rev, myLastReply(info), group);
+    loadDiff(b, rev, myLastReply(info), group);
     loadCommit(rev, group);
 
     if (loaded) {
@@ -644,19 +647,57 @@ public class ChangeScreen2 extends Screen {
   }
 
   private RevisionInfo resolveRevisionToDisplay(ChangeInfo info) {
-    if (revision == null) {
-      revision = info.current_revision();
-    } else if (!info.revisions().containsKey(revision)) {
+    RevisionInfo rev = resolveRevisionOrPatchSetId(info, revision,
+        info.current_revision());
+    if (rev != null) {
+      revision = rev.name();
+      return rev;
+    }
+
+    // the revision is not visible to the calling user (maybe it is a draft?)
+    // or the change is corrupt, take the last revision that was returned,
+    // if no revision was returned display an error
+    JsArray<RevisionInfo> revisions = info.revisions().values();
+    if (revisions.length() > 0) {
+      RevisionInfo.sortRevisionInfoByNumber(revisions);
+      rev = revisions.get(revisions.length() - 1);
+      revision = rev.name();
+      return rev;
+    } else {
+      new ErrorDialog(
+          Resources.M.changeWithNoRevisions(info.legacy_id().get())).center();
+      throw new IllegalStateException("no revision, cannot proceed");
+    }
+  }
+
+  /**
+   *
+   * Resolve a revision or patch set id string to RevisionInfo.
+   * When this view is created from the changes table, revision
+   * is passed as a real revision.
+   * When this view is created from side by side (by closing it with 'u')
+   * patch set id is passed.
+   *
+   * @param info change info
+   * @param revOrId revision or patch set id
+   * @param defaultValue value returned when rev is null
+   * @return resolved revision or default value
+   */
+  private RevisionInfo resolveRevisionOrPatchSetId(ChangeInfo info,
+      String revOrId, String defaultValue) {
+    if (revOrId == null) {
+      revOrId = defaultValue;
+    } else if (!info.revisions().containsKey(revOrId)) {
       JsArray<RevisionInfo> list = info.revisions().values();
       for (int i = 0; i < list.length(); i++) {
         RevisionInfo r = list.get(i);
-        if (revision.equals(String.valueOf(r._number()))) {
-          revision = r.name();
+        if (revOrId.equals(String.valueOf(r._number()))) {
+          revOrId = r.name();
           break;
         }
       }
     }
-    return info.revision(revision);
+    return revOrId != null ? info.revision(revOrId) : null;
   }
 
   private void renderChangeInfo(ChangeInfo info) {
@@ -753,6 +794,7 @@ public class ChangeScreen2 extends Screen {
   private void renderDiffBaseListBox(ChangeInfo info) {
     JsArray<RevisionInfo> list = info.revisions().values();
     RevisionInfo.sortRevisionInfoByNumber(list);
+    int selectedIdx = list.length();
     for (int i = list.length() - 1; i >= 0; i--) {
       RevisionInfo r = list.get(i);
       diffBase.addItem(
@@ -762,6 +804,9 @@ public class ChangeScreen2 extends Screen {
         SelectElement.as(diffBase.getElement()).getOptions()
             .getItem(diffBase.getItemCount() - 1).setDisabled(true);
       }
+      if (base != null && base.equals(String.valueOf(r._number()))) {
+        selectedIdx = diffBase.getItemCount() - 1;
+      }
     }
 
     RevisionInfo rev = info.revisions().get(revision);
@@ -769,7 +814,8 @@ public class ChangeScreen2 extends Screen {
     diffBase.addItem(
       parents.length() > 1 ? Util.C.autoMerge() : Util.C.baseDiffItem(),
       "");
-    diffBase.setSelectedIndex(diffBase.getItemCount() - 1);
+
+    diffBase.setSelectedIndex(selectedIdx);
   }
 
   void showUpdates(ChangeInfo newInfo) {
@@ -814,4 +860,8 @@ public class ChangeScreen2 extends Screen {
       handlers.add(UserActivityMonitor.addValueChangeHandler(updateCheck));
     }
   }
+
+  private static String normalize(String r) {
+    return r != null && !r.isEmpty() ? r : null;
+  }
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/Header.java

@@ -80,6 +80,7 @@ class Header extends Composite {
     SafeHtml.setInnerHTML(filePath, formatPath(path));
     up.setTargetHistoryToken(PageLinks.toChange(
         patchSetId.getParentKey(),
+        base != null ? String.valueOf(base.get()) : null,
         String.valueOf(patchSetId.get())));
   }
 

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/SideBySide2.java

@@ -1054,10 +1054,11 @@ public class SideBySide2 extends Screen {
   private Runnable upToChange(final boolean openReplyBox) {
     return new Runnable() {
       public void run() {
+        String b = base != null ? String.valueOf(base.get()) : null;
         String rev = String.valueOf(revision.get());
         Gerrit.display(
           PageLinks.toChange(changeId, rev),
-          new ChangeScreen2(changeId, rev, openReplyBox));
+          new ChangeScreen2(changeId, b, rev, openReplyBox));
       }
     };
   }