Backport some changes for overlays (#3691)

* Backport some changes for overlays

* Format

Author: wu-hui

firebase-firestore/src/main/java/com/google/firebase/firestore/local/LocalDocumentsView.java

@@ -91,7 +91,7 @@ Document getDocument(DocumentKey key) {
     Overlay overlay = documentOverlayCache.getOverlay(key);
     MutableDocument document = getBaseDocument(key, overlay);
     if (overlay != null) {
-      overlay.getMutation().applyToLocalView(document, null, Timestamp.now());
+      overlay.getMutation().applyToLocalView(document, FieldMask.EMPTY, Timestamp.now());
     }
     return document;
   }
@@ -171,7 +171,9 @@ private Map<DocumentKey, OverlayedDocument> computeViews(
         recalculateDocuments.put(doc.getKey(), doc);
       } else if (overlay != null) {
         mutatedFields.put(doc.getKey(), overlay.getMutation().getFieldMask());
-        overlay.getMutation().applyToLocalView(doc, null, Timestamp.now());
+        overlay
+            .getMutation()
+            .applyToLocalView(doc, overlay.getMutation().getFieldMask(), Timestamp.now());
       }
     }
 
@@ -375,7 +377,9 @@ private ImmutableSortedMap<DocumentKey, Document> getDocumentsMatchingCollection
     for (Map.Entry<DocumentKey, MutableDocument> docEntry : remoteDocuments.entrySet()) {
       Overlay overlay = overlays.get(docEntry.getKey());
       if (overlay != null) {
-        overlay.getMutation().applyToLocalView(docEntry.getValue(), null, Timestamp.now());
+        overlay
+            .getMutation()
+            .applyToLocalView(docEntry.getValue(), FieldMask.EMPTY, Timestamp.now());
       }
       // Finally, insert the documents that still match the query
       if (query.matches(docEntry.getValue())) {

firebase-firestore/src/test/java/com/google/firebase/firestore/local/LocalStoreTestCase.java

@@ -1337,16 +1337,17 @@ public void testHoldsBackTransforms() {
             emptyList()));
     assertChanged(doc("foo/bar", 1, map("sum", 0, "array_union", new ArrayList<>())));
 
-    writeMutations(
-        asList(
-            patchMutation("foo/bar", map("sum", FieldValue.increment(1))),
-            patchMutation("foo/bar", map("array_union", FieldValue.arrayUnion("foo")))));
+    writeMutation(patchMutation("foo/bar", map("sum", FieldValue.increment(1))));
+    assertChanged(
+        doc("foo/bar", 1, map("sum", 1, "array_union", new ArrayList<>())).setHasLocalMutations());
+
+    writeMutation(patchMutation("foo/bar", map("array_union", FieldValue.arrayUnion("foo"))));
     assertChanged(
         doc("foo/bar", 1, map("sum", 1, "array_union", Collections.singletonList("foo")))
             .setHasLocalMutations());
 
-    // The sum transform is not idempotent and the backend's updated value is ignored. The
-    // ArrayUnion transform is recomputed and includes the backend value.
+    // The sum transform and array union transform make the SDK ignore the
+    // backend's updated value.
     applyRemoteEvent(
         addedRemoteEvent(
             doc("foo/bar", 2, map("sum", 1337, "array_union", Collections.singletonList("bar"))),
@@ -1355,10 +1356,18 @@ public void testHoldsBackTransforms() {
     assertChanged(
         doc("foo/bar", 2, map("sum", 1, "array_union", asList("foo"))).setHasLocalMutations());
 
-    acknowledgeMutationWithTransformResults(3, 1338, asList("bar", "foo"));
+    // With a field transform acknowledgement, the overlay is recalculated with
+    // remaining local mutations.
+    acknowledgeMutationWithTransformResults(3, 1338);
     assertChanged(
         doc("foo/bar", 3, map("sum", 1338, "array_union", asList("bar", "foo")))
             .setReadTime(new SnapshotVersion(new Timestamp(0, 3000)))
+            .setHasLocalMutations());
+
+    acknowledgeMutationWithTransformResults(4, asList("bar", "foo"));
+    assertChanged(
+        doc("foo/bar", 4, map("sum", 1338, "array_union", asList("bar", "foo")))
+            .setReadTime(new SnapshotVersion(new Timestamp(0, 4000)))
             .setHasCommittedMutations());
   }