Fix browser NPE when ChangeCache is incomplete

The ChangeCache is buggy and does not always populate its
contents. Unfortunately it is also designed to be unable to
load missing contents on demand, causing consumers to NPE.
ConfigInfoCache is a better design for this sort of lazy
loading and reuse of data.

ChangeCache can be missing information if:

  1) opens side-by-side view in a new tab;
  2) user presses 'r' to open publish comment screen

Instead of using the unreliable ChangeCache, stub out a
ChangeDetail to feed to the info block on the publish
comments screen.

Bug: issue 2039
Change-Id: Id542528d93af1cab49b001ca5e90addfc5d05b78
(cherry picked from commit f646aa77fb67b73c8724d7a632cafd441365e901)

4 files changed, 15 insertions, 12 deletions

diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDescriptionBlock.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDescriptionBlock.java
index 5cd6cdb131..8395907a3e 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDescriptionBlock.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDescriptionBlock.java
@@ -15,8 +15,8 @@
 package com.google.gerrit.client.changes;
 
 import com.google.gerrit.common.data.AccountInfoCache;
+import com.google.gerrit.common.data.ChangeDetail;
 import com.google.gerrit.common.data.SubmitTypeRecord;
-import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSetInfo;
 import com.google.gwt.user.client.ui.Composite;
 import com.google.gwt.user.client.ui.HorizontalPanel;
@@ -36,11 +36,11 @@ public class ChangeDescriptionBlock extends Composite {
     initWidget(hp);
   }
 
-  public void display(Change chg, Boolean starred, Boolean canEditCommitMessage,
+  public void display(ChangeDetail chg, Boolean starred, Boolean canEditCommitMessage,
       PatchSetInfo info,
       final AccountInfoCache acc, SubmitTypeRecord submitTypeRecord) {
     infoBlock.display(chg, acc, submitTypeRecord);
-    messageBlock.display(chg.currentPatchSetId(), starred,
+    messageBlock.display(chg.getChange().currentPatchSetId(), starred,
       canEditCommitMessage,  info.getMessage());
   }
 }
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeInfoBlock.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeInfoBlock.java
index e4dbc3218d..afc17f7c60 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeInfoBlock.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeInfoBlock.java
@@ -95,8 +95,9 @@ public class ChangeInfoBlock extends Composite {
     table.getCellFormatter().addStyleName(row, 0, Gerrit.RESOURCES.css().header());
   }
 
-  public void display(final Change chg, final AccountInfoCache acc,
-      SubmitTypeRecord submitTypeRecord) {
+  public void display(final ChangeDetail changeDetail,
+      final AccountInfoCache acc, SubmitTypeRecord submitTypeRecord) {
+    final Change chg = changeDetail.getChange();
     final Branch.NameKey dst = chg.getDest();
 
     CopyableLabel changeIdLabel =
@@ -114,7 +115,7 @@ public class ChangeInfoBlock extends Composite {
 
     table.setWidget(R_BRANCH, 1, new BranchLink(dst.getShortName(), chg
         .getProject(), chg.getStatus(), dst.get(), null));
-    table.setWidget(R_TOPIC, 1, topic(chg));
+    table.setWidget(R_TOPIC, 1, topic(changeDetail));
     table.setText(R_UPLOADED, 1, mediumFormat(chg.getCreatedOn()));
     table.setText(R_UPDATED, 1, mediumFormat(chg.getLastUpdatedOn()));
     table.setText(R_STATUS, 1, Util.toLongString(chg.getStatus()));
@@ -146,7 +147,8 @@ public class ChangeInfoBlock extends Composite {
     }
   }
 
-  public Widget topic(final Change chg) {
+  public Widget topic(final ChangeDetail changeDetail) {
+    final Change chg = changeDetail.getChange();
     final Branch.NameKey dst = chg.getDest();
 
     FlowPanel fp = new FlowPanel();
@@ -154,9 +156,6 @@ public class ChangeInfoBlock extends Composite {
     fp.add(new BranchLink(chg.getTopic(), chg.getProject(), chg.getStatus(),
            dst.get(), chg.getTopic()));
 
-    ChangeDetailCache detailCache = ChangeCache.get(chg.getId()).getChangeDetailCache();
-    ChangeDetail changeDetail = detailCache.get();
-
     if (changeDetail.canEditTopicName()) {
       final Image edit = new Image(Gerrit.RESOURCES.edit());
       edit.addStyleName(Gerrit.RESOURCES.css().link());
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeScreen.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeScreen.java
index 7983512898..91c885691a 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeScreen.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeScreen.java
@@ -301,7 +301,7 @@ public class ChangeScreen extends Screen
 
     dependencies.setAccountInfoCache(detail.getAccounts());
 
-    descriptionBlock.display(detail.getChange(),
+    descriptionBlock.display(detail,
         detail.isStarred(),
         detail.canEditCommitMessage(),
         detail.getCurrentPatchSetDetail().getInfo(),
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PublishCommentScreen.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PublishCommentScreen.java
index 97949e3b8b..7f61977c38 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PublishCommentScreen.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/PublishCommentScreen.java
@@ -30,6 +30,7 @@ import com.google.gerrit.client.ui.CommentLinkProcessor;
 import com.google.gerrit.client.ui.PatchLink;
 import com.google.gerrit.client.ui.SmallHeading;
 import com.google.gerrit.common.PageLinks;
+import com.google.gerrit.common.data.ChangeDetail;
 import com.google.gerrit.common.data.PatchSetPublishDetail;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Patch;
@@ -298,9 +299,12 @@ public class PublishCommentScreen extends AccountScreen implements
   }
 
   private void display(final PatchSetPublishDetail r) {
+    ChangeDetail changeDetail = new ChangeDetail();
+    changeDetail.setChange(r.getChange());
+
     setPageTitle(Util.M.publishComments(r.getChange().getKey().abbreviate(),
         patchSetId.get()));
-    descBlock.display(r.getChange(), null, false, r.getPatchSetInfo(), r.getAccounts(),
+    descBlock.display(changeDetail, null, false, r.getPatchSetInfo(), r.getAccounts(),
         r.getSubmitTypeRecord());
 
     if (r.getChange().getStatus().isOpen()) {