diff --git a/Documentation/config-labels.txt b/Documentation/config-labels.txt
index f5346c1..b4e65b0 100644
--- a/Documentation/config-labels.txt
+++ b/Documentation/config-labels.txt
@@ -280,7 +280,7 @@
 
 Gerrit currently supports the following predicates:
 
-==== change-kind:{REWORK,TRIVIAL_REBASE,MERGE_FIRST_PARENT_UPDATE,NO_CODE_CHANGE,NO_CHANGE}
+==== changekind:{REWORK,TRIVIAL_REBASE,MERGE_FIRST_PARENT_UPDATE,NO_CODE_CHANGE,NO_CHANGE}
 
 Matches if the diff between two patch sets was of a certain change kind.
 
diff --git a/java/com/google/gerrit/server/CommentsUtil.java b/java/com/google/gerrit/server/CommentsUtil.java
index b752791..344549e 100644
--- a/java/com/google/gerrit/server/CommentsUtil.java
+++ b/java/com/google/gerrit/server/CommentsUtil.java
@@ -42,8 +42,9 @@
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.notedb.ChangeUpdate;
-import com.google.gerrit.server.patch.PatchListCache;
-import com.google.gerrit.server.patch.PatchListNotAvailableException;
+import com.google.gerrit.server.patch.DiffNotAvailableException;
+import com.google.gerrit.server.patch.DiffOperations;
+import com.google.gerrit.server.patch.filediff.FileDiffOutput;
 import com.google.gerrit.server.update.ChangeContext;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
@@ -52,6 +53,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
@@ -108,21 +110,21 @@
 
   private static final Ordering<Comparable<?>> NULLS_FIRST = Ordering.natural().nullsFirst();
 
+  private final DiffOperations diffOperations;
   private final GitRepositoryManager repoManager;
   private final AllUsersName allUsers;
   private final String serverId;
-  private final PatchListCache patchListCache;
 
   @Inject
   CommentsUtil(
+      DiffOperations diffOperations,
       GitRepositoryManager repoManager,
       AllUsersName allUsers,
-      @GerritServerId String serverId,
-      PatchListCache patchListCache) {
+      @GerritServerId String serverId) {
+    this.diffOperations = diffOperations;
     this.repoManager = repoManager;
     this.allUsers = allUsers;
     this.serverId = serverId;
-    this.patchListCache = patchListCache;
   }
 
   public HumanComment newHumanComment(
@@ -411,7 +413,7 @@
         int parentNumber = Math.abs(side);
         return resolveParentCommit(change.getProject(), patchset, parentNumber);
       }
-      return Optional.of(resolveAutoMergeCommit(change, patchset));
+      return Optional.ofNullable(resolveAutoMergeCommit(change, patchset));
     }
     return Optional.of(patchset.commitId());
   }
@@ -429,12 +431,18 @@
     }
   }
 
+  @Nullable
   private ObjectId resolveAutoMergeCommit(Change change, PatchSet patchset) {
     try {
       // TODO(ghareeb): Adjust after the auto-merge code was moved out of the diff caches. Also
       // unignore the test in PortedCommentsIT.
-      return patchListCache.getOldId(change, patchset, null);
-    } catch (PatchListNotAvailableException e) {
+      Map<String, FileDiffOutput> modifiedFiles =
+          diffOperations.listModifiedFilesAgainstParent(
+              change.getProject(), patchset.commitId(), /* parentNum= */ null);
+      return modifiedFiles.isEmpty()
+          ? null
+          : modifiedFiles.values().iterator().next().oldCommitId();
+    } catch (DiffNotAvailableException e) {
       throw new StorageException(e);
     }
   }
diff --git a/java/com/google/gerrit/server/patch/AutoMerger.java b/java/com/google/gerrit/server/patch/AutoMerger.java
index b99e2d2..8d1e0ff 100644
--- a/java/com/google/gerrit/server/patch/AutoMerger.java
+++ b/java/com/google/gerrit/server/patch/AutoMerger.java
@@ -31,6 +31,8 @@
 import com.google.gerrit.server.logging.Metadata;
 import com.google.gerrit.server.update.RepoView;
 import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.util.Optional;
 import org.eclipse.jgit.dircache.DirCache;
@@ -70,6 +72,7 @@
  * <p>The second point means that these commits are referenced from NoteDb. The consequence of this
  * is that these refs should never be deleted.
  */
+@Singleton
 public class AutoMerger {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
@@ -88,7 +91,7 @@
 
   private final Counter1<OperationType> counter;
   private final Timer1<OperationType> latency;
-  private final PersonIdent gerritIdent;
+  private final Provider<PersonIdent> gerritIdentProvider;
   private final boolean save;
   private final ThreeWayMergeStrategy configuredMergeStrategy;
 
@@ -96,7 +99,7 @@
   AutoMerger(
       MetricMaker metricMaker,
       @GerritServerConfig Config cfg,
-      @GerritPersonIdent PersonIdent gerritIdent) {
+      @GerritPersonIdent Provider<PersonIdent> gerritIdentProvider) {
     this.counter =
         metricMaker.newCounter(
             "git/auto-merge/num_operations",
@@ -110,7 +113,7 @@
                 .setUnit("milliseconds"),
             Field.ofEnum(OperationType.class, "type", Metadata.Builder::operationName).build());
     this.save = cacheAutomerge(cfg);
-    this.gerritIdent = gerritIdent;
+    this.gerritIdentProvider = gerritIdentProvider;
     this.configuredMergeStrategy = MergeUtil.getMergeStrategy(cfg);
   }
 
@@ -224,7 +227,9 @@
     // the input commit, using the server name and timezone.
     PersonIdent ident =
         new PersonIdent(
-            gerritIdent, merge.getCommitterIdent().getWhen(), gerritIdent.getTimeZone());
+            gerritIdentProvider.get(),
+            merge.getCommitterIdent().getWhen(),
+            gerritIdentProvider.get().getTimeZone());
     CommitBuilder cb = new CommitBuilder();
     cb.setAuthor(ident);
     cb.setCommitter(ident);
diff --git a/java/com/google/gerrit/server/patch/BaseCommitUtil.java b/java/com/google/gerrit/server/patch/BaseCommitUtil.java
index 7c06a62..dd930378 100644
--- a/java/com/google/gerrit/server/patch/BaseCommitUtil.java
+++ b/java/com/google/gerrit/server/patch/BaseCommitUtil.java
@@ -21,6 +21,7 @@
 import com.google.gerrit.server.git.InMemoryInserter;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Constants;
@@ -34,6 +35,7 @@
 import org.eclipse.jgit.revwalk.RevWalk;
 
 /** A utility class for computing the base commit / parent for a specific patchset commit. */
+@Singleton
 class BaseCommitUtil {
   private final AutoMerger autoMerger;
   private final ThreeWayMergeStrategy mergeStrategy;
diff --git a/java/com/google/gerrit/server/patch/DiffOperationsImpl.java b/java/com/google/gerrit/server/patch/DiffOperationsImpl.java
index dbbb7a6..fd30868 100644
--- a/java/com/google/gerrit/server/patch/DiffOperationsImpl.java
+++ b/java/com/google/gerrit/server/patch/DiffOperationsImpl.java
@@ -44,6 +44,7 @@
 import com.google.gerrit.server.patch.gitfilediff.GitFileDiffCacheImpl.DiffAlgorithm;
 import com.google.inject.Inject;
 import com.google.inject.Module;
+import com.google.inject.Singleton;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
@@ -60,6 +61,7 @@
  * Provides different file diff operations. Uses the underlying Git/Gerrit caches to speed up the
  * diff computation.
  */
+@Singleton
 public class DiffOperationsImpl implements DiffOperations {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
diff --git a/java/com/google/gerrit/server/patch/diff/ModifiedFilesCacheImpl.java b/java/com/google/gerrit/server/patch/diff/ModifiedFilesCacheImpl.java
index 6023c0e..e168386 100644
--- a/java/com/google/gerrit/server/patch/diff/ModifiedFilesCacheImpl.java
+++ b/java/com/google/gerrit/server/patch/diff/ModifiedFilesCacheImpl.java
@@ -34,6 +34,7 @@
 import com.google.gerrit.server.patch.gitdiff.ModifiedFile;
 import com.google.inject.Inject;
 import com.google.inject.Module;
+import com.google.inject.Singleton;
 import com.google.inject.TypeLiteral;
 import com.google.inject.name.Named;
 import java.io.IOException;
@@ -56,6 +57,7 @@
  * and the result will be exactly the same as the caller can get from {@link
  * GitModifiedFilesCache#get(GitModifiedFilesCacheKey)}
  */
+@Singleton
 public class ModifiedFilesCacheImpl implements ModifiedFilesCache {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
diff --git a/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java b/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
index 2133474..0794775 100644
--- a/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
+++ b/java/com/google/gerrit/server/patch/filediff/FileDiffCacheImpl.java
@@ -44,6 +44,7 @@
 import com.google.gerrit.server.patch.gitfilediff.GitFileDiffCacheImpl.DiffAlgorithmFactory;
 import com.google.inject.Inject;
 import com.google.inject.Module;
+import com.google.inject.Singleton;
 import com.google.inject.name.Named;
 import java.io.IOException;
 import java.util.ArrayList;
@@ -76,6 +77,7 @@
  * org.eclipse.jgit.lib.Constants#EMPTY_TREE_ID}, the git diff will be evaluated against the empty
  * tree.
  */
+@Singleton
 public class FileDiffCacheImpl implements FileDiffCache {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
diff --git a/java/com/google/gerrit/server/patch/gitdiff/GitModifiedFilesCacheImpl.java b/java/com/google/gerrit/server/patch/gitdiff/GitModifiedFilesCacheImpl.java
index b3b82bb..9b96da1 100644
--- a/java/com/google/gerrit/server/patch/gitdiff/GitModifiedFilesCacheImpl.java
+++ b/java/com/google/gerrit/server/patch/gitdiff/GitModifiedFilesCacheImpl.java
@@ -29,6 +29,7 @@
 import com.google.gerrit.server.patch.DiffNotAvailableException;
 import com.google.inject.Inject;
 import com.google.inject.Module;
+import com.google.inject.Singleton;
 import com.google.inject.TypeLiteral;
 import com.google.inject.name.Named;
 import java.io.IOException;
@@ -43,6 +44,7 @@
 import org.eclipse.jgit.util.io.DisabledOutputStream;
 
 /** Implementation of the {@link GitModifiedFilesCache} */
+@Singleton
 public class GitModifiedFilesCacheImpl implements GitModifiedFilesCache {
   private static final String GIT_MODIFIED_FILES = "git_modified_files";
   private static final ImmutableMap<ChangeType, Patch.ChangeType> changeTypeMap =
diff --git a/java/com/google/gerrit/server/patch/gitfilediff/GitFileDiffCacheImpl.java b/java/com/google/gerrit/server/patch/gitfilediff/GitFileDiffCacheImpl.java
index 97cf37d32..4bc6b87 100644
--- a/java/com/google/gerrit/server/patch/gitfilediff/GitFileDiffCacheImpl.java
+++ b/java/com/google/gerrit/server/patch/gitfilediff/GitFileDiffCacheImpl.java
@@ -31,6 +31,7 @@
 import com.google.gerrit.server.patch.DiffNotAvailableException;
 import com.google.inject.Inject;
 import com.google.inject.Module;
+import com.google.inject.Singleton;
 import com.google.inject.name.Named;
 import java.io.IOException;
 import java.util.Collection;
@@ -52,6 +53,7 @@
 import org.eclipse.jgit.util.io.DisabledOutputStream;
 
 /** Implementation of the {@link GitFileDiffCache} */
+@Singleton
 public class GitFileDiffCacheImpl implements GitFileDiffCache {
   private static final String GIT_DIFF = "git_file_diff";
 
diff --git a/java/com/google/gerrit/server/query/approval/ApprovalQueryBuilder.java b/java/com/google/gerrit/server/query/approval/ApprovalQueryBuilder.java
index c3594f5..f412cc7 100644
--- a/java/com/google/gerrit/server/query/approval/ApprovalQueryBuilder.java
+++ b/java/com/google/gerrit/server/query/approval/ApprovalQueryBuilder.java
@@ -51,7 +51,7 @@
   }
 
   @Operator
-  public Predicate<ApprovalContext> changeKind(String term) throws QueryParseException {
+  public Predicate<ApprovalContext> changekind(String term) throws QueryParseException {
     return new ChangeKindPredicate(toEnumValue(ChangeKind.class, term));
   }
 
diff --git a/java/com/google/gerrit/server/restapi/change/CommentPorter.java b/java/com/google/gerrit/server/restapi/change/CommentPorter.java
index d1d4544..35d512a 100644
--- a/java/com/google/gerrit/server/restapi/change/CommentPorter.java
+++ b/java/com/google/gerrit/server/restapi/change/CommentPorter.java
@@ -29,7 +29,6 @@
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Project;
-import com.google.gerrit.extensions.client.DiffPreferencesInfo.Whitespace;
 import com.google.gerrit.metrics.Counter0;
 import com.google.gerrit.metrics.Description;
 import com.google.gerrit.metrics.MetricMaker;
@@ -39,16 +38,17 @@
 import com.google.gerrit.server.logging.TraceContext.TraceTimer;
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.patch.DiffMappings;
+import com.google.gerrit.server.patch.DiffNotAvailableException;
+import com.google.gerrit.server.patch.DiffOperations;
 import com.google.gerrit.server.patch.GitPositionTransformer;
 import com.google.gerrit.server.patch.GitPositionTransformer.BestPositionOnConflict;
 import com.google.gerrit.server.patch.GitPositionTransformer.FileMapping;
 import com.google.gerrit.server.patch.GitPositionTransformer.Mapping;
 import com.google.gerrit.server.patch.GitPositionTransformer.Position;
 import com.google.gerrit.server.patch.GitPositionTransformer.PositionedEntity;
-import com.google.gerrit.server.patch.PatchList;
-import com.google.gerrit.server.patch.PatchListCache;
-import com.google.gerrit.server.patch.PatchListKey;
-import com.google.gerrit.server.patch.PatchListNotAvailableException;
+import com.google.gerrit.server.patch.filediff.FileDiffOutput;
+import com.google.gerrit.server.patch.filediff.FileEdits;
+import com.google.gerrit.server.patch.filediff.TaggedEdit;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.util.List;
@@ -102,15 +102,15 @@
     }
   }
 
+  private final DiffOperations diffOperations;
   private final GitPositionTransformer positionTransformer =
       new GitPositionTransformer(BestPositionOnConflict.INSTANCE);
-  private final PatchListCache patchListCache;
   private final CommentsUtil commentsUtil;
   private final Metrics metrics;
 
   @Inject
-  public CommentPorter(PatchListCache patchListCache, CommentsUtil commentsUtil, Metrics metrics) {
-    this.patchListCache = patchListCache;
+  public CommentPorter(DiffOperations diffOperations, CommentsUtil commentsUtil, Metrics metrics) {
+    this.diffOperations = diffOperations;
     this.commentsUtil = commentsUtil;
     this.metrics = metrics;
   }
@@ -283,7 +283,7 @@
       PatchSet originalPatchset,
       PatchSet targetPatchset,
       short side)
-      throws PatchListNotAvailableException {
+      throws DiffNotAvailableException {
     try (TraceTimer ignored =
         TraceContext.newTimer(
             "Loading commit mappings",
@@ -311,18 +311,26 @@
 
   private ImmutableSet<Mapping> loadCommitMappings(
       Project.NameKey project, ObjectId originalCommit, ObjectId targetCommit)
-      throws PatchListNotAvailableException {
+      throws DiffNotAvailableException {
     try (TraceTimer ignored =
         TraceContext.newTimer(
             "Computing diffs", Metadata.builder().commit(originalCommit.name()).build())) {
-      PatchList patchList =
-          patchListCache.get(
-              PatchListKey.againstCommit(originalCommit, targetCommit, Whitespace.IGNORE_NONE),
-              project);
-      return patchList.getPatches().stream().map(DiffMappings::toMapping).collect(toImmutableSet());
+      Map<String, FileDiffOutput> modifiedFiles =
+          diffOperations.listModifiedFiles(project, originalCommit, targetCommit);
+      return modifiedFiles.values().stream()
+          .map(CommentPorter::getFileEdits)
+          .map(DiffMappings::toMapping)
+          .collect(toImmutableSet());
     }
   }
 
+  private static FileEdits getFileEdits(FileDiffOutput fileDiffOutput) {
+    return FileEdits.create(
+        fileDiffOutput.edits().stream().map(TaggedEdit::edit).collect(toImmutableList()),
+        fileDiffOutput.oldPath(),
+        fileDiffOutput.newPath());
+  }
+
   private ImmutableSet<Mapping> getFallbackMappings(List<HumanComment> comments) {
     // Consider all files as deleted. -> Comments will be ported to the fallback destination, which
     // currently are patchset-level comments.
diff --git a/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java b/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
index ebb2f38..46f9c5a 100644
--- a/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
+++ b/javatests/com/google/gerrit/server/restapi/change/CommentPorterTest.java
@@ -22,6 +22,7 @@
 import static org.mockito.Mockito.when;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.truth.Correspondence;
 import com.google.gerrit.entities.Account;
@@ -35,12 +36,8 @@
 import com.google.gerrit.metrics.DisabledMetricMaker;
 import com.google.gerrit.server.CommentsUtil;
 import com.google.gerrit.server.notedb.ChangeNotes;
-import com.google.gerrit.server.patch.ComparisonType;
-import com.google.gerrit.server.patch.PatchList;
-import com.google.gerrit.server.patch.PatchListCache;
-import com.google.gerrit.server.patch.PatchListEntry;
-import com.google.gerrit.server.patch.PatchListKey;
-import com.google.gerrit.server.patch.PatchListNotAvailableException;
+import com.google.gerrit.server.patch.DiffNotAvailableException;
+import com.google.gerrit.server.patch.DiffOperations;
 import com.google.gerrit.server.restapi.change.CommentPorter.Metrics;
 import com.google.gerrit.truth.NullAwareCorrespondence;
 import java.sql.Timestamp;
@@ -60,7 +57,7 @@
 
   @Rule public final MockitoRule mockito = MockitoJUnit.rule();
 
-  @Mock private PatchListCache patchListCache;
+  @Mock private DiffOperations diffOperations;
   @Mock private CommentsUtil commentsUtil;
 
   private static final CommentPorter.Metrics metrics = new Metrics(new DisabledMetricMaker());
@@ -76,12 +73,13 @@
     PatchSet patchset2 = createPatchset(PatchSet.id(changeId, 2));
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset1, patchset2);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     HumanComment comment = createComment(patchset1.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenReturn(Optional.of(dummyObjectId));
-    when(patchListCache.get(any(PatchListKey.class), any(Project.NameKey.class)))
-        .thenThrow(PatchListNotAvailableException.class);
+    when(diffOperations.listModifiedFiles(
+            any(Project.NameKey.class), any(ObjectId.class), any(ObjectId.class)))
+        .thenThrow(DiffNotAvailableException.class);
     ImmutableList<HumanComment> portedComments =
         commentPorter.portComments(
             changeNotes, patchset2, ImmutableList.of(comment), ImmutableList.of());
@@ -98,11 +96,12 @@
     PatchSet patchset2 = createPatchset(PatchSet.id(changeId, 2));
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset1, patchset2);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     HumanComment comment = createComment(patchset1.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenReturn(Optional.of(dummyObjectId));
-    when(patchListCache.get(any(PatchListKey.class), any(Project.NameKey.class)))
+    when(diffOperations.listModifiedFiles(
+            any(Project.NameKey.class), any(ObjectId.class), any(ObjectId.class)))
         .thenThrow(IllegalStateException.class);
     ImmutableList<HumanComment> portedComments =
         commentPorter.portComments(
@@ -120,7 +119,7 @@
     PatchSet patchset2 = createPatchset(PatchSet.id(changeId, 2));
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset1, patchset2);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     HumanComment comment = createComment(patchset1.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenThrow(IllegalStateException.class);
@@ -140,11 +139,12 @@
     PatchSet patchset2 = createPatchset(PatchSet.id(changeId, 2));
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset1, patchset2);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     HumanComment comment = createComment(patchset1.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenReturn(Optional.of(dummyObjectId));
-    when(patchListCache.get(any(PatchListKey.class), any(Project.NameKey.class)))
+    when(diffOperations.listModifiedFiles(
+            any(Project.NameKey.class), any(ObjectId.class), any(ObjectId.class)))
         .thenThrow(IllegalStateException.class);
     ImmutableList<HumanComment> portedComments =
         commentPorter.portComments(
@@ -165,17 +165,17 @@
     PatchSet patchset3 = createPatchset(PatchSet.id(changeId, 3));
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset1, patchset2, patchset3);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     // Place the comments on different patchsets to have two different diff requests.
     HumanComment comment1 = createComment(patchset1.id(), "myFile");
     HumanComment comment2 = createComment(patchset2.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenReturn(Optional.of(dummyObjectId));
-    PatchList emptyDiff = getEmptyDiff();
     // Throw an exception on the first diff request but return an actual value on the second.
-    when(patchListCache.get(any(PatchListKey.class), any(Project.NameKey.class)))
+    when(diffOperations.listModifiedFiles(
+            any(Project.NameKey.class), any(ObjectId.class), any(ObjectId.class)))
         .thenThrow(IllegalStateException.class)
-        .thenReturn(emptyDiff);
+        .thenReturn(ImmutableMap.of());
     ImmutableList<HumanComment> portedComments =
         commentPorter.portComments(
             changeNotes, patchset3, ImmutableList.of(comment1, comment2), ImmutableList.of());
@@ -195,13 +195,13 @@
     // Leave out patchset 1 (e.g. reserved for draft patchsets in the past).
     ChangeNotes changeNotes = mockChangeNotes(project, change, patchset2);
 
-    CommentPorter commentPorter = new CommentPorter(patchListCache, commentsUtil, metrics);
+    CommentPorter commentPorter = new CommentPorter(diffOperations, commentsUtil, metrics);
     HumanComment comment = createComment(patchset1.id(), "myFile");
     when(commentsUtil.determineCommitId(any(), any(), anyShort()))
         .thenReturn(Optional.of(dummyObjectId));
-    PatchList emptyDiff = getEmptyDiff();
-    when(patchListCache.get(any(PatchListKey.class), any(Project.NameKey.class)))
-        .thenReturn(emptyDiff);
+    when(diffOperations.listModifiedFiles(
+            any(Project.NameKey.class), any(ObjectId.class), any(ObjectId.class)))
+        .thenReturn(ImmutableMap.of());
     ImmutableList<HumanComment> portedComments =
         commentPorter.portComments(
             changeNotes, patchset2, ImmutableList.of(comment), ImmutableList.of());
@@ -260,13 +260,4 @@
   private Correspondence<HumanComment, String> hasFilePath() {
     return NullAwareCorrespondence.transforming(comment -> comment.key.filename, "hasFilePath");
   }
-
-  private PatchList getEmptyDiff() {
-    return new PatchList(
-        dummyObjectId,
-        dummyObjectId,
-        false,
-        ComparisonType.againstOtherPatchSet(),
-        new PatchListEntry[0]);
-  }
 }
diff --git a/polygerrit-ui/app/api/diff.ts b/polygerrit-ui/app/api/diff.ts
index ad83fb8..724141f 100644
--- a/polygerrit-ui/app/api/diff.ts
+++ b/polygerrit-ui/app/api/diff.ts
@@ -406,17 +406,26 @@
   ): void;
 }
 
-// The current setup requires API users to register GrDiff instances with the
-// cursor, but we do not at this point want to expose the API that GrDiffCursor
-// uses to the public as it is likely to change. So for now, we allow any type
-// and cast. This works fine so long as API users do provide whatever the
-// gr-diff tag creates.
-export type GrDiff = unknown;
+/** An instance of the GrDiff Webcomponent */
+export interface GrDiff extends HTMLElement {
+  /**
+   * Return line number element for reading only,
+   *
+   * This is useful e.g. to determine where on screen certain lines are,
+   * whether they are covered up etc.
+   */
+  getLineNumEls(side: Side): readonly HTMLElement[];
+}
 
 /** A service to interact with the line cursor in gr-diff instances. */
 export declare interface GrDiffCursor {
-  replaceDiffs(diffs: GrDiff[]): void;
-  unregisterDiff(diff: GrDiff): void;
+  // The current setup requires API users to register GrDiff instances with the
+  // cursor, but we do not at this point want to expose the API that GrDiffCursor
+  // uses to the public as it is likely to change. So for now, we allow any type
+  // and cast. This works fine so long as API users do provide whatever the
+  // gr-diff tag creates.
+  replaceDiffs(diffs: unknown[]): void;
+  unregisterDiff(diff: unknown): void;
 
   isAtStart(): boolean;
   isAtEnd(): boolean;
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.ts
index 06087ed..8ee6a3f 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-item/gr-change-list-item_html.ts
@@ -158,7 +158,7 @@
     hidden$="[[isColumnHidden('Owner', visibleChangeTableColumns)]]"
   >
     <gr-account-link
-      highlight-attention
+      highlightAttention
       change="[[change]]"
       account="[[change.owner]]"
     ></gr-account-link>
@@ -189,10 +189,10 @@
         indexAs="index"
       >
         <gr-account-link
-          hide-avatar=""
-          hide-status=""
-          first-name
-          highlight-attention
+          hideAvatar=""
+          hideStatus=""
+          firstName
+          highlightAttention
           change="[[change]]"
           account="[[reviewer]]"
         ></gr-account-link
diff --git a/polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.js b/polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.ts
similarity index 77%
rename from polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.js
rename to polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.ts
index 9dbcd29..42aed07 100644
--- a/polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.js
+++ b/polygerrit-ui/app/elements/change-list/gr-create-commands-dialog/gr-create-commands-dialog_test.ts
@@ -17,11 +17,12 @@
 
 import '../../../test/common-test-setup-karma.js';
 import './gr-create-commands-dialog.js';
+import {GrCreateCommandsDialog} from './gr-create-commands-dialog.js';
 
 const basicFixture = fixtureFromElement('gr-create-commands-dialog');
 
 suite('gr-create-commands-dialog tests', () => {
-  let element;
+  let element: GrCreateCommandsDialog;
 
   setup(() => {
     element = basicFixture.instantiate();
@@ -29,12 +30,12 @@
 
   test('_computePushCommand', () => {
     element.branch = 'master';
-    assert.equal(element._pushCommand,
-        'git push origin HEAD:refs/for/master');
+    assert.equal(element._pushCommand, 'git push origin HEAD:refs/for/master');
 
     element.branch = 'stable-2.15';
-    assert.equal(element._pushCommand,
-        'git push origin HEAD:refs/for/stable-2.15');
+    assert.equal(
+      element._pushCommand,
+      'git push origin HEAD:refs/for/stable-2.15'
+    );
   });
 });
-
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_test.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_test.ts
index ab8e404..516a31e 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata_test.ts
@@ -939,7 +939,7 @@
   });
 
   suite('plugin endpoints', () => {
-    test('endpoint params', done => {
+    test('endpoint params', async () => {
       element.change = createParsedChange();
       element.revision = createRevision();
       interface MetadataGrEndpointDecorator extends GrEndpointDecorator {
@@ -961,12 +961,10 @@
         'http://some/plugins/url.js'
       );
       getPluginLoader().loadPlugins([]);
-      flush(() => {
-        assert.strictEqual(hookEl!.plugin, plugin);
-        assert.strictEqual(hookEl!.change, element.change);
-        assert.strictEqual(hookEl!.revision, element.revision);
-        done();
-      });
+      await flush();
+      assert.strictEqual(hookEl!.plugin, plugin!);
+      assert.strictEqual(hookEl!.change, element.change);
+      assert.strictEqual(hookEl!.revision, element.revision);
     });
   });
 });
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
index 58cf489..8b37cf0 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
@@ -171,7 +171,7 @@
 import {takeUntil} from 'rxjs/operators';
 import {aPluginHasRegistered$} from '../../../services/checks/checks-model';
 import {Subject} from 'rxjs';
-import {debounce, DelayedTask} from '../../../utils/async-util';
+import {debounce, DelayedTask, throttleWrap} from '../../../utils/async-util';
 import {Interaction, Timing} from '../../../constants/reporting';
 import {ChangeStates} from '../../shared/gr-change-status/gr-change-status';
 import {getRevertCreatedChangeIds} from '../../../utils/message-util';
@@ -603,7 +603,7 @@
   /** @override */
   connectedCallback() {
     super.connectedCallback();
-    this._throttledToggleChangeStar = this._throttleWrap(e =>
+    this._throttledToggleChangeStar = throttleWrap(e =>
       this._handleToggleChangeStar(e as CustomKeyboardEvent)
     );
     this._getServerConfig().then(config => {
diff --git a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog_test.ts b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog_test.ts
index 52ec8af..ea3c01d 100644
--- a/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-download-dialog/gr-download-dialog_test.ts
@@ -31,6 +31,7 @@
   RepoName,
 } from '../../../types/common';
 import {GrDownloadDialog} from './gr-download-dialog';
+import {mockPromise} from '../../../test/test-utils';
 
 const basicFixture = fixtureFromElement('gr-download-dialog');
 
@@ -168,14 +169,16 @@
       );
     });
 
-    test('close event', done => {
+    test('close event', async () => {
+      const closeCalled = mockPromise();
       element.addEventListener('close', () => {
-        done();
+        closeCalled.resolve();
       });
       const closeButton = element.shadowRoot!.querySelector(
         '.closeButtonContainer gr-button'
       );
       tap(closeButton!);
+      await closeCalled;
     });
   });
 
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_html.ts b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_html.ts
index 8b9b80c..be3a0be 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header_html.ts
@@ -167,6 +167,30 @@
           <span class="separator"></span>
         </span>
       </template>
+      <div class="fileViewActions">
+        <span class="fileViewActionsLabel">Diff view:</span>
+        <gr-diff-mode-selector
+          id="modeSelect"
+          mode="{{diffViewMode}}"
+          save-on-change="[[!diffPrefsDisabled]]"
+        ></gr-diff-mode-selector>
+        <span
+          id="diffPrefsContainer"
+          class="hideOnEdit"
+          hidden$="[[_computePrefsButtonHidden(diffPrefs, diffPrefsDisabled)]]"
+          hidden=""
+        >
+          <gr-button
+            link=""
+            has-tooltip=""
+            title="Diff preferences"
+            class="prefsButton desktop"
+            on-click="_handlePrefsTap"
+            ><iron-icon icon="gr-icons:settings"></iron-icon
+          ></gr-button>
+        </span>
+      </div>
+      <span class="separator"></span>
       <span class="downloadContainer desktop">
         <gr-button
           link=""
@@ -209,30 +233,6 @@
           Bulk actions disabled because there are too many files.
         </div>
       </template>
-      <div class="fileViewActions">
-        <span class="separator"></span>
-        <span class="fileViewActionsLabel">Diff view:</span>
-        <gr-diff-mode-selector
-          id="modeSelect"
-          mode="{{diffViewMode}}"
-          save-on-change="[[!diffPrefsDisabled]]"
-        ></gr-diff-mode-selector>
-        <span
-          id="diffPrefsContainer"
-          class="hideOnEdit"
-          hidden$="[[_computePrefsButtonHidden(diffPrefs, diffPrefsDisabled)]]"
-          hidden=""
-        >
-          <gr-button
-            link=""
-            has-tooltip=""
-            title="Diff preferences"
-            class="prefsButton desktop"
-            on-click="_handlePrefsTap"
-            ><iron-icon icon="gr-icons:settings"></iron-icon
-          ></gr-button>
-        </span>
-      </div>
     </div>
   </div>
 `;
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
index ae9af4a..15bc6bf 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
@@ -599,7 +599,7 @@
       resetPlugins();
     });
 
-    test('endpoint params', done => {
+    test('endpoint params', async () => {
       element.change = {...createParsedChange(), labels: {}};
       interface RelatedChangesListGrEndpointDecorator
         extends GrEndpointDecorator {
@@ -620,11 +620,9 @@
         'http://some/plugins/url1.js'
       );
       getPluginLoader().loadPlugins([]);
-      flush(() => {
-        assert.strictEqual(hookEl.plugin, plugin);
-        assert.strictEqual(hookEl.change, element.change);
-        done();
-      });
+      await flush();
+      assert.strictEqual(hookEl!.plugin, plugin!);
+      assert.strictEqual(hookEl!.change, element.change);
     });
   });
 });
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.ts b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.ts
index 4b57651..354d360 100644
--- a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list_test.ts
@@ -17,7 +17,11 @@
 
 import '../../../test/common-test-setup-karma';
 import './gr-reviewer-list';
-import {queryAndAssert, stubRestApi} from '../../../test/test-utils';
+import {
+  mockPromise,
+  queryAndAssert,
+  stubRestApi,
+} from '../../../test/test-utils';
 import {GrReviewerList} from './gr-reviewer-list';
 import {
   createAccountDetailWithId,
@@ -53,12 +57,14 @@
     );
   });
 
-  test('add reviewer button opens reply dialog', done => {
+  test('add reviewer button opens reply dialog', async () => {
+    const dialogShown = mockPromise();
     element.addEventListener('show-reply-dialog', () => {
-      done();
+      dialogShown.resolve();
     });
-    flush();
+    await flush();
     tap(queryAndAssert(element, '.addReviewer'));
+    await dialogShown;
   });
 
   test('only show remove for removable reviewers', () => {
diff --git a/polygerrit-ui/app/elements/checks/gr-hovercard-run_test.js b/polygerrit-ui/app/elements/checks/gr-hovercard-run_test.ts
similarity index 78%
rename from polygerrit-ui/app/elements/checks/gr-hovercard-run_test.js
rename to polygerrit-ui/app/elements/checks/gr-hovercard-run_test.ts
index 9c77654..80d8e5e 100644
--- a/polygerrit-ui/app/elements/checks/gr-hovercard-run_test.js
+++ b/polygerrit-ui/app/elements/checks/gr-hovercard-run_test.ts
@@ -18,24 +18,25 @@
 import '../../test/common-test-setup-karma.js';
 import './gr-hovercard-run.js';
 import {html} from '@polymer/polymer/lib/utils/html-tag.js';
+import {GrHovercardRun} from './gr-hovercard-run.js';
 
 const basicFixture = fixtureFromTemplate(html`
-<gr-hovercard-run class="hovered"></gr-hovercard-run>
+  <gr-hovercard-run class="hovered"></gr-hovercard-run>
 `);
 
 suite('gr-hovercard-run tests', () => {
-  let element;
+  let element: GrHovercardRun;
 
   setup(async () => {
-    element = basicFixture.instantiate();
+    element = basicFixture.instantiate() as GrHovercardRun;
     await flush();
   });
 
   teardown(() => {
-    element.hide({});
+    element.hide();
   });
 
   test('hovercard is shown', () => {
+    assert.equal(element.computeIcon(), '');
   });
 });
-
diff --git a/polygerrit-ui/app/elements/core/gr-error-dialog/gr-error-dialog_test.ts b/polygerrit-ui/app/elements/core/gr-error-dialog/gr-error-dialog_test.ts
index fa57a23..2dec8d2 100644
--- a/polygerrit-ui/app/elements/core/gr-error-dialog/gr-error-dialog_test.ts
+++ b/polygerrit-ui/app/elements/core/gr-error-dialog/gr-error-dialog_test.ts
@@ -17,7 +17,7 @@
 
 import * as MockInteractions from '@polymer/iron-test-helpers/mock-interactions';
 import '../../../test/common-test-setup-karma';
-import {queryAndAssert} from '../../../test/test-utils';
+import {mockPromise, queryAndAssert} from '../../../test/test-utils';
 import {GrDialog} from '../../shared/gr-dialog/gr-dialog';
 import {GrErrorDialog} from './gr-error-dialog';
 
@@ -30,10 +30,12 @@
     element = basicFixture.instantiate();
   });
 
-  test('dismiss tap fires event', done => {
-    element.addEventListener('dismiss', () => done());
+  test('dismiss tap fires event', async () => {
+    const dismissCalled = mockPromise();
+    element.addEventListener('dismiss', () => dismissCalled.resolve());
     MockInteractions.tap(
       (queryAndAssert(element, '#dialog') as GrDialog).$.confirm
     );
+    await dismissCalled;
   });
 });
diff --git a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
index 8f9dfe2..8352319 100644
--- a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
+++ b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager.ts
@@ -75,6 +75,37 @@
   };
 }
 
+export function constructServerErrorMsg({
+  errorText,
+  status,
+  statusText,
+  url,
+  trace,
+  tip,
+}: ErrorMsg) {
+  let err = '';
+  if (tip) {
+    err += `${tip}\n\n`;
+  }
+  err += `Error ${status}`;
+  if (statusText) {
+    err += ` (${statusText})`;
+  }
+  if (errorText || url) {
+    err += ': ';
+  }
+  if (errorText) {
+    err += errorText;
+  }
+  if (url) {
+    err += `\nEndpoint: ${url}`;
+  }
+  if (trace) {
+    err += `\nTrace Id: ${trace}`;
+  }
+  return err;
+}
+
 @customElement('gr-error-manager')
 export class GrErrorManager extends PolymerElement {
   static get template() {
@@ -221,7 +252,7 @@
           this._showQuotaExceeded({status, statusText});
         } else {
           this._showErrorDialog(
-            this._constructServerErrorMsg({
+            constructServerErrorMsg({
               status,
               statusText,
               errorText,
@@ -247,7 +278,7 @@
         ? 'You might have not enough privileges.'
         : 'You might have not enough privileges. Sign in and try again.';
       this._showErrorDialog(
-        this._constructServerErrorMsg({
+        constructServerErrorMsg({
           status,
           statusText,
           errorText,
@@ -266,7 +297,7 @@
     const tip = 'Try again later';
     const errorText = 'Too many requests from this client';
     this._showErrorDialog(
-      this._constructServerErrorMsg({
+      constructServerErrorMsg({
         status,
         statusText,
         errorText,
@@ -275,37 +306,6 @@
     );
   }
 
-  _constructServerErrorMsg({
-    errorText,
-    status,
-    statusText,
-    url,
-    trace,
-    tip,
-  }: ErrorMsg) {
-    let err = '';
-    if (tip) {
-      err += `${tip}\n\n`;
-    }
-    err += `Error ${status}`;
-    if (statusText) {
-      err += ` (${statusText})`;
-    }
-    if (errorText || url) {
-      err += ': ';
-    }
-    if (errorText) {
-      err += errorText;
-    }
-    if (url) {
-      err += `\nEndpoint: ${url}`;
-    }
-    if (trace) {
-      err += `\nTrace Id: ${trace}`;
-    }
-    return err;
-  }
-
   private readonly handleShowAlert = (e: CustomEvent<ShowAlertEventDetail>) => {
     this._showAlert(
       e.detail.message,
diff --git a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager_test.js b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager_test.js
index fe4d9da..4cf15b4 100644
--- a/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager_test.js
+++ b/polygerrit-ui/app/elements/core/gr-error-manager/gr-error-manager_test.js
@@ -18,7 +18,7 @@
 import '../../../test/common-test-setup-karma.js';
 import './gr-error-manager.js';
 import {_testOnly_initGerritPluginApi} from '../../shared/gr-js-api-interface/gr-gerrit.js';
-import {__testOnly_ErrorType} from './gr-error-manager.js';
+import {constructServerErrorMsg, __testOnly_ErrorType} from './gr-error-manager.js';
 import {stubRestApi} from '../../../test/test-utils.js';
 import {appContext} from '../../../services/app-context.js';
 import {createPreferences} from '../../../test/test-data-generators.js';
@@ -132,27 +132,26 @@
       });
     });
 
-    test('_constructServerErrorMsg', () => {
+    test('constructServerErrorMsg', () => {
       const errorText = 'change conflicts';
       const status = 409;
       const statusText = 'Conflict';
       const url = '/my/test/url';
 
-      assert.equal(element._constructServerErrorMsg({status}),
+      assert.equal(constructServerErrorMsg({status}),
           'Error 409');
-      assert.equal(element._constructServerErrorMsg({status, url}),
+      assert.equal(constructServerErrorMsg({status, url}),
           'Error 409: \nEndpoint: /my/test/url');
-      assert.equal(element.
-          _constructServerErrorMsg({status, statusText, url}),
-      'Error 409 (Conflict): \nEndpoint: /my/test/url');
-      assert.equal(element._constructServerErrorMsg({
+      assert.equal(constructServerErrorMsg({status, statusText, url}),
+          'Error 409 (Conflict): \nEndpoint: /my/test/url');
+      assert.equal(constructServerErrorMsg({
         status,
         statusText,
         errorText,
         url,
       }), 'Error 409 (Conflict): change conflicts' +
       '\nEndpoint: /my/test/url');
-      assert.equal(element._constructServerErrorMsg({
+      assert.equal(constructServerErrorMsg({
         status,
         statusText,
         errorText,
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
index dacd8e7..9004517 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
@@ -106,6 +106,7 @@
 import {assertIsDefined} from '../../../utils/common-util';
 import {toggleClass, getKeyboardEvent} from '../../../utils/dom-util';
 import {CursorMoveResult} from '../../../api/core';
+import {throttleWrap} from '../../../utils/async-util';
 
 const ERR_REVIEW_STATUS = 'Couldn’t change file review status.';
 const MSG_LOADING_BLAME = 'Loading blame...';
@@ -342,7 +343,7 @@
   /** @override */
   connectedCallback() {
     super.connectedCallback();
-    this._throttledToggleFileReviewed = this._throttleWrap(e =>
+    this._throttledToggleFileReviewed = throttleWrap(e =>
       this._handleToggleFileReviewed(e as CustomKeyboardEvent)
     );
     this._getLoggedIn().then(loggedIn => {
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
index 7c437fd..0b42f9f 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.ts
@@ -69,6 +69,7 @@
 import {
   CreateCommentEventDetail as CreateCommentEventDetailApi,
   RenderPreferences,
+  GrDiff as GrDiffApi,
 } from '../../../api/diff';
 import {isSafari, toggleClass} from '../../../utils/dom-util';
 import {assertIsDefined} from '../../../utils/common-util';
@@ -109,7 +110,7 @@
 }
 
 @customElement('gr-diff')
-export class GrDiff extends PolymerElement {
+export class GrDiff extends PolymerElement implements GrDiffApi {
   static get template() {
     return htmlTemplate;
   }
@@ -322,6 +323,12 @@
     super.disconnectedCallback();
   }
 
+  getLineNumEls(side: Side): HTMLElement[] {
+    return Array.from(
+      this.root?.querySelectorAll<HTMLElement>(`.lineNum.${side}`) ?? []
+    );
+  }
+
   showNoChangeMessage(
     loading?: boolean,
     prefs?: DiffPreferencesInfo,
diff --git a/polygerrit-ui/app/elements/gr-app-element.ts b/polygerrit-ui/app/elements/gr-app-element.ts
index be9c7c5..c9f0506 100644
--- a/polygerrit-ui/app/elements/gr-app-element.ts
+++ b/polygerrit-ui/app/elements/gr-app-element.ts
@@ -55,7 +55,10 @@
   ElementPropertyDeepChange,
   ServerInfo,
 } from '../types/common';
-import {GrErrorManager} from './core/gr-error-manager/gr-error-manager';
+import {
+  constructServerErrorMsg,
+  GrErrorManager,
+} from './core/gr-error-manager/gr-error-manager';
 import {GrOverlay} from './shared/gr-overlay/gr-overlay';
 import {GrRegistrationDialog} from './settings/gr-registration-dialog/gr-registration-dialog';
 import {
@@ -565,7 +568,15 @@
       err.emoji = 'o_O';
       if (response) {
         response.text().then(text => {
-          err.moreInfo = text;
+          const trace =
+            response.headers && response.headers.get('X-Gerrit-Trace');
+          const {status, statusText} = response;
+          err.moreInfo = constructServerErrorMsg({
+            status,
+            statusText,
+            errorText: text,
+            trace,
+          });
           this._lastError = err;
         });
       }
diff --git a/polygerrit-ui/app/elements/settings/gr-agreements-list/gr-agreements-list_test.ts b/polygerrit-ui/app/elements/settings/gr-agreements-list/gr-agreements-list_test.ts
index f08976f..4891759 100644
--- a/polygerrit-ui/app/elements/settings/gr-agreements-list/gr-agreements-list_test.ts
+++ b/polygerrit-ui/app/elements/settings/gr-agreements-list/gr-agreements-list_test.ts
@@ -25,7 +25,7 @@
 suite('gr-agreements-list tests', () => {
   let element: GrAgreementsList;
 
-  setup(done => {
+  setup(async () => {
     const agreements: ContributorAgreementInfo[] = [
       {
         url: 'some url',
@@ -38,9 +38,8 @@
 
     element = basicFixture.instantiate();
 
-    element.loadData().then(() => {
-      flush(done);
-    });
+    await element.loadData();
+    await flush();
   });
 
   test('renders', () => {
diff --git a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view_test.ts b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view_test.ts
index 9f54cd1..d634483 100644
--- a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view_test.ts
+++ b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view_test.ts
@@ -125,16 +125,15 @@
     },
   ];
 
-  setup(done => {
+  setup(async () => {
     stubRestApi('getConfig').returns(Promise.resolve(config));
     stubRestApi('getAccountGroups').returns(Promise.resolve(groups));
     stubRestApi('getAccountAgreements').returns(
       Promise.resolve(signedAgreements)
     );
     element = basicFixture.instantiate();
-    element.loadData().then(() => {
-      flush(done);
-    });
+    await element.loadData();
+    await flush();
   });
 
   test('renders as expected with signed agreement', () => {
diff --git a/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link.ts b/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link.ts
index 5c4b76a..944c3df 100644
--- a/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link.ts
+++ b/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link.ts
@@ -16,19 +16,12 @@
  */
 
 import '../gr-account-label/gr-account-label';
-import '../../../styles/shared-styles';
-import {PolymerElement} from '@polymer/polymer/polymer-element';
-import {htmlTemplate} from './gr-account-link_html';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
-import {customElement, property} from '@polymer/decorators';
 import {AccountInfo, ChangeInfo} from '../../../types/common';
+import {css, customElement, html, LitElement, property} from 'lit-element';
 
 @customElement('gr-account-link')
-class GrAccountLink extends PolymerElement {
-  static get template() {
-    return htmlTemplate;
-  }
-
+class GrAccountLink extends LitElement {
   @property({type: String})
   voteableText?: string;
 
@@ -70,6 +63,45 @@
   @property({type: Boolean})
   firstName = false;
 
+  static get styles() {
+    return [
+      css`
+        :host {
+          display: inline-block;
+          vertical-align: top;
+        }
+        a {
+          color: var(--primary-text-color);
+          text-decoration: none;
+        }
+        gr-account-label {
+          --gr-account-label-text-hover-style: {
+            text-decoration: underline;
+          }
+        }
+      `,
+    ];
+  }
+
+  render() {
+    if (!this.account) return;
+    return html`<span>
+      <a href="${this._computeOwnerLink(this.account)}">
+        <gr-account-label
+          .account="${this.account}"
+          .change="${this.change}"
+          ?force-attention=${this.forceAttention}
+          ?highlight-attention=${this.highlightAttention}
+          ?hide-avatar=${this.hideAvatar}
+          ?hide-status=${this.hideStatus}
+          ?first-name=${this.firstName}
+          .voteable-text=${this.voteableText}
+        >
+        </gr-account-label>
+      </a>
+    </span>`;
+  }
+
   _computeOwnerLink(account?: AccountInfo) {
     if (!account) {
       return;
diff --git a/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link_html.ts b/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link_html.ts
deleted file mode 100644
index 98a6e77..0000000
--- a/polygerrit-ui/app/elements/shared/gr-account-link/gr-account-link_html.ts
+++ /dev/null
@@ -1,50 +0,0 @@
-/**
- * @license
- * Copyright (C) 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import {html} from '@polymer/polymer/lib/utils/html-tag';
-
-export const htmlTemplate = html`
-  <style>
-    :host {
-      display: inline-block;
-      vertical-align: top;
-    }
-    a {
-      color: var(--primary-text-color);
-      text-decoration: none;
-    }
-    gr-account-label {
-      --gr-account-label-text-hover-style: {
-        text-decoration: underline;
-      }
-    }
-  </style>
-  <span>
-    <a href$="[[_computeOwnerLink(account)]]">
-      <gr-account-label
-        account="[[account]]"
-        change="[[change]]"
-        force-attention="[[forceAttention]]"
-        highlight-attention="[[highlightAttention]]"
-        hide-avatar="[[hideAvatar]]"
-        hide-status="[[hideStatus]]"
-        first-name="[[firstName]]"
-        voteable-text="[[voteableText]]"
-      >
-      </gr-account-label>
-    </a>
-  </span>
-`;
diff --git a/polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.js b/polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.ts
similarity index 82%
rename from polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.js
rename to polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.ts
index 11ec496..cf0c34a 100644
--- a/polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-alert/gr-alert_test.ts
@@ -17,8 +17,11 @@
 
 import '../../../test/common-test-setup-karma.js';
 import './gr-alert.js';
+import {GrAlert} from './gr-alert.js';
+import * as MockInteractions from '@polymer/iron-test-helpers/mock-interactions';
+
 suite('gr-alert tests', () => {
-  let element;
+  let element: GrAlert;
 
   setup(() => {
     element = document.createElement('gr-alert');
@@ -32,7 +35,7 @@
 
   test('show/hide', () => {
     assert.isNull(element.parentNode);
-    element.show();
+    element.show('Alert text');
     assert.equal(element.parentNode, document.body);
     element.updateStyles({'--gr-alert-transition-duration': '0ms'});
     element.hide();
@@ -41,11 +44,10 @@
 
   test('action event', () => {
     const spy = sinon.spy();
-    element.show();
+    element.show('Alert text');
     element._actionCallback = spy;
     assert.isFalse(spy.called);
-    MockInteractions.tap(element.shadowRoot.querySelector('.action'));
+    MockInteractions.tap(element.shadowRoot!.querySelector('.action')!);
     assert.isTrue(spy.called);
   });
 });
-
diff --git a/polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.js b/polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.ts
similarity index 80%
rename from polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.js
rename to polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.ts
index dd2b98a..972e02c 100644
--- a/polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-linked-chip/gr-linked-chip_test.ts
@@ -15,13 +15,15 @@
  * limitations under the License.
  */
 
-import '../../../test/common-test-setup-karma.js';
-import './gr-linked-chip.js';
+import '../../../test/common-test-setup-karma';
+import './gr-linked-chip';
+import {GrLinkedChip} from './gr-linked-chip';
+import * as MockInteractions from '@polymer/iron-test-helpers/mock-interactions';
 
 const basicFixture = fixtureFromElement('gr-linked-chip');
 
 suite('gr-linked-chip tests', () => {
-  let element;
+  let element: GrLinkedChip;
 
   setup(() => {
     element = basicFixture.instantiate();
@@ -35,4 +37,3 @@
     assert.isTrue(spy.called);
   });
 });
-
diff --git a/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.js b/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.ts
similarity index 78%
rename from polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.js
rename to polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.ts
index de9f243..1a7d2cd 100644
--- a/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.js
+++ b/polygerrit-ui/app/elements/shared/gr-shell-command/gr-shell-command_test.ts
@@ -17,25 +17,26 @@
 
 import '../../../test/common-test-setup-karma.js';
 import './gr-shell-command.js';
+import {GrShellCommand} from './gr-shell-command.js';
 
 const basicFixture = fixtureFromElement('gr-shell-command');
 
 suite('gr-shell-command tests', () => {
-  let element;
+  let element: GrShellCommand;
 
   setup(() => {
     element = basicFixture.instantiate();
-    element.text = `git fetch http://gerrit@localhost:8080/a/test-project
+    element.command = `git fetch http://gerrit@localhost:8080/a/test-project
         refs/changes/05/5/1 && git checkout FETCH_HEAD`;
     flush();
   });
 
   test('focusOnCopy', () => {
-    const focusStub = sinon.stub(element.shadowRoot
-        .querySelector('gr-copy-clipboard'),
-    'focusOnCopy');
+    const focusStub = sinon.stub(
+      element.shadowRoot!.querySelector('gr-copy-clipboard')!,
+      'focusOnCopy'
+    );
     element.focusOnCopy();
     assert.isTrue(focusStub.called);
   });
 });
-
diff --git a/polygerrit-ui/app/mixins/keyboard-shortcut-mixin/keyboard-shortcut-mixin.ts b/polygerrit-ui/app/mixins/keyboard-shortcut-mixin/keyboard-shortcut-mixin.ts
index 555a256..3d5a208 100644
--- a/polygerrit-ui/app/mixins/keyboard-shortcut-mixin/keyboard-shortcut-mixin.ts
+++ b/polygerrit-ui/app/mixins/keyboard-shortcut-mixin/keyboard-shortcut-mixin.ts
@@ -120,8 +120,6 @@
 
 const V_KEY_TIMEOUT_MS = 1000;
 
-const THROTTLE_INTERVAL_MS = 500;
-
 /**
  * Enum for all shortcut sections, where that shortcut should be applied to.
  */
@@ -675,8 +673,6 @@
     if (!bindings) {
       return null;
     }
-    // TODO(TS): should check base on length to differentiate two
-    // cases
     if (bindings[0] === SPECIAL_SHORTCUT.GO_KEY) {
       return bindings
         .slice(1)
@@ -851,13 +847,6 @@
         return getKeyboardEvent(e);
       }
 
-      // TODO(TS): maybe remove, no reference in the code base
-      getRootTarget(e: CustomKeyboardEvent) {
-        // TODO(TS): worth checking if we can limit this to EventApi only
-        // dom currently returns DomNativeApi|EventApi
-        return (dom(getKeyboardEvent(e)) as EventApi).rootTarget;
-      }
-
       bindShortcut(shortcut: Shortcut, ...bindings: string[]) {
         shortcutManager.bindShortcut(shortcut, ...bindings);
       }
@@ -868,20 +857,6 @@
         return desc && shortcut ? `${desc} (shortcut: ${shortcut})` : '';
       }
 
-      _throttleWrap(fn: (e: Event) => void) {
-        let lastCall: number | undefined;
-        return (e: Event) => {
-          if (
-            lastCall !== undefined &&
-            Date.now() - lastCall < THROTTLE_INTERVAL_MS
-          ) {
-            return;
-          }
-          lastCall = Date.now();
-          fn(e);
-        };
-      }
-
       _addOwnKeyBindings(shortcut: Shortcut, handler: string) {
         const bindings = shortcutManager.getBindingsForShortcut(shortcut);
         if (!bindings) {
@@ -1128,8 +1103,6 @@
   modifierPressed(event: CustomKeyboardEvent): boolean;
   addKeyboardShortcutDirectoryListener(listener: ShortcutListener): void;
   removeKeyboardShortcutDirectoryListener(listener: ShortcutListener): void;
-  // TODO(TS): Remove underscore. Apparently not a private method.
-  _throttleWrap(eventListener: EventListener): EventListener;
 }
 
 export function _testOnly_getShortcutManagerInstance() {
diff --git a/polygerrit-ui/app/services/checks/checks-model.ts b/polygerrit-ui/app/services/checks/checks-model.ts
index 5d3da42..22c2381 100644
--- a/polygerrit-ui/app/services/checks/checks-model.ts
+++ b/polygerrit-ui/app/services/checks/checks-model.ts
@@ -261,10 +261,13 @@
 
 // Must only be used by the checks service or whatever is in control of this
 // model.
-export function updateStateSetProvider(pluginName: string) {
+export function updateStateSetProvider(
+  pluginName: string,
+  patchset: ChecksPatchset
+) {
   const nextState = {...privateState$.getValue()};
-  nextState.pluginStateLatest = {...nextState.pluginStateLatest};
-  nextState.pluginStateLatest[pluginName] = {
+  const pluginState = getPluginState(nextState, patchset);
+  pluginState[pluginName] = {
     pluginName,
     loading: false,
     runs: [],
diff --git a/polygerrit-ui/app/services/checks/checks-service.ts b/polygerrit-ui/app/services/checks/checks-service.ts
index e1d435b..d683514 100644
--- a/polygerrit-ui/app/services/checks/checks-service.ts
+++ b/polygerrit-ui/app/services/checks/checks-service.ts
@@ -118,7 +118,8 @@
   ) {
     this.providers[pluginName] = provider;
     this.reloadSubjects[pluginName] = new BehaviorSubject<void>(undefined);
-    updateStateSetProvider(pluginName);
+    updateStateSetProvider(pluginName, ChecksPatchset.LATEST);
+    updateStateSetProvider(pluginName, ChecksPatchset.SELECTED);
     this.initFetchingOfData(pluginName, config, ChecksPatchset.LATEST);
     this.initFetchingOfData(pluginName, config, ChecksPatchset.SELECTED);
   }
diff --git a/polygerrit-ui/app/services/flags/flags_test.js b/polygerrit-ui/app/services/flags/flags_test.ts
similarity index 85%
rename from polygerrit-ui/app/services/flags/flags_test.js
rename to polygerrit-ui/app/services/flags/flags_test.ts
index 33508af..8827368 100644
--- a/polygerrit-ui/app/services/flags/flags_test.js
+++ b/polygerrit-ui/app/services/flags/flags_test.ts
@@ -15,12 +15,12 @@
  * limitations under the License.
  */
 
-import '../../test/common-test-setup-karma.js';
-import {FlagsServiceImplementation} from './flags_impl.js';
+import '../../test/common-test-setup-karma';
+import {FlagsServiceImplementation} from './flags_impl';
 
 suite('flags tests', () => {
-  let originalEnabledExperiments;
-  let flags;
+  let originalEnabledExperiments: string[];
+  let flags: FlagsServiceImplementation;
 
   suiteSetup(() => {
     originalEnabledExperiments = window.ENABLED_EXPERIMENTS;
@@ -41,4 +41,3 @@
     assert.deepEqual(flags.enabledExperiments, ['a']);
   });
 });
-
diff --git a/polygerrit-ui/app/utils/account-util_test.js b/polygerrit-ui/app/utils/account-util_test.ts
similarity index 75%
rename from polygerrit-ui/app/utils/account-util_test.js
rename to polygerrit-ui/app/utils/account-util_test.ts
index 0628f2d..835cd6d 100644
--- a/polygerrit-ui/app/utils/account-util_test.js
+++ b/polygerrit-ui/app/utils/account-util_test.ts
@@ -15,13 +15,12 @@
  * limitations under the License.
  */
 
-import '../test/common-test-setup-karma.js';
-import {isServiceUser, removeServiceUsers} from './account-util.js';
-import {AccountTag} from '../constants/constants.js';
+import '../test/common-test-setup-karma';
+import {isServiceUser, removeServiceUsers} from './account-util';
+import {AccountTag} from '../constants/constants';
 
 const EMPTY = {};
 const ERNIE = {name: 'Ernie'};
-const KERMIT = {name: 'Kermit', tags: ['FROG']};
 const SERVY = {name: 'Servy', tags: [AccountTag.SERVICE_USER]};
 const BOTTY = {name: 'Botty', tags: [AccountTag.SERVICE_USER]};
 
@@ -30,17 +29,17 @@
     assert.isFalse(isServiceUser());
     assert.isFalse(isServiceUser(EMPTY));
     assert.isFalse(isServiceUser(ERNIE));
-    assert.isFalse(isServiceUser(KERMIT));
     assert.isTrue(isServiceUser(SERVY));
     assert.isTrue(isServiceUser(BOTTY));
   });
 
   test('removeServiceUsers', () => {
     assert.sameMembers(removeServiceUsers([]), []);
-    assert.sameMembers(removeServiceUsers([EMPTY, ERNIE, KERMIT]),
-        [EMPTY, ERNIE, KERMIT]);
+    assert.sameMembers(removeServiceUsers([EMPTY, ERNIE]), [EMPTY, ERNIE]);
     assert.sameMembers(removeServiceUsers([SERVY, BOTTY]), []);
-    assert.sameMembers(removeServiceUsers([EMPTY, SERVY, ERNIE, BOTTY, KERMIT]),
-        [EMPTY, ERNIE, KERMIT]);
+    assert.sameMembers(removeServiceUsers([EMPTY, SERVY, ERNIE, BOTTY]), [
+      EMPTY,
+      ERNIE,
+    ]);
   });
 });
diff --git a/polygerrit-ui/app/utils/async-util.ts b/polygerrit-ui/app/utils/async-util.ts
index 2b36fee..c82f5e4 100644
--- a/polygerrit-ui/app/utils/async-util.ts
+++ b/polygerrit-ui/app/utils/async-util.ts
@@ -110,3 +110,23 @@
   existingTask?.cancel();
   return new DelayedTask(callback, waitMs);
 }
+
+const THROTTLE_INTERVAL_MS = 500;
+
+/**
+ * Ensure only one call is made within THROTTLE_INTERVAL_MS and any call within
+ * this interval is ignored
+ */
+export function throttleWrap(fn: (e: Event) => void) {
+  let lastCall: number | undefined;
+  return (e: Event) => {
+    if (
+      lastCall !== undefined &&
+      Date.now() - lastCall < THROTTLE_INTERVAL_MS
+    ) {
+      return;
+    }
+    lastCall = Date.now();
+    fn(e);
+  };
+}
diff --git a/polygerrit-ui/app/utils/safe-types-util_test.js b/polygerrit-ui/app/utils/safe-types-util_test.ts
similarity index 83%
rename from polygerrit-ui/app/utils/safe-types-util_test.js
rename to polygerrit-ui/app/utils/safe-types-util_test.ts
index e3968d0..03253e0 100644
--- a/polygerrit-ui/app/utils/safe-types-util_test.js
+++ b/polygerrit-ui/app/utils/safe-types-util_test.ts
@@ -15,12 +15,12 @@
  * limitations under the License.
  */
 
-import '../test/common-test-setup-karma.js';
-import {safeTypesBridge, _testOnly_SafeUrl} from './safe-types-util.js';
+import '../test/common-test-setup-karma';
+import {safeTypesBridge, _testOnly_SafeUrl} from './safe-types-util';
 
 suite('safe-types-util tests', () => {
   test('SafeUrl accepts valid urls', () => {
-    function accepts(url) {
+    function accepts(url: string) {
       const safeUrl = new _testOnly_SafeUrl(url);
       assert.isOk(safeUrl);
       assert.equal(url, safeUrl.toString());
@@ -35,8 +35,10 @@
   });
 
   test('SafeUrl rejects invalid urls', () => {
-    function rejects(url) {
-      assert.throws(() => { new _testOnly_SafeUrl(url); });
+    function rejects(url: string) {
+      assert.throws(() => {
+        new _testOnly_SafeUrl(url);
+      });
     }
     rejects('javascript://alert("evil");');
     rejects('ftp:example.com');
@@ -44,13 +46,14 @@
   });
 
   suite('safeTypesBridge', () => {
-    function acceptsString(value, type) {
-      assert.equal(safeTypesBridge(value, type),
-          value);
+    function acceptsString(value: string, type: string) {
+      assert.equal(safeTypesBridge(value, type), value);
     }
 
-    function rejects(value, type) {
-      assert.throws(() => { safeTypesBridge(value, type); });
+    function rejects(value: unknown, type: string) {
+      assert.throws(() => {
+        safeTypesBridge(value, type);
+      });
     }
 
     test('accepts valid URL strings', () => {