Overlay on top of mutation list

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

@@ -25,6 +25,7 @@
 import com.google.firebase.firestore.model.MutableDocument;
 import com.google.firebase.firestore.model.ResourcePath;
 import com.google.firebase.firestore.model.SnapshotVersion;
+import com.google.firebase.firestore.model.mutation.FieldMask;
 import com.google.firebase.firestore.model.mutation.Mutation;
 import com.google.firebase.firestore.model.mutation.MutationBatch;
 import com.google.firebase.firestore.model.mutation.PatchMutation;
@@ -209,7 +210,9 @@ private ImmutableSortedMap<DocumentKey, Document> getDocumentsMatchingCollection
           document = MutableDocument.newInvalidDocument(key);
           remoteDocuments = remoteDocuments.insert(key, document);
         }
-        mutation.applyToLocalView(document, batch.getLocalWriteTime());
+        // TODO(Overlay): Here we should be reading overlay mutation and apply that instead.
+        mutation.applyToLocalView(
+            document, FieldMask.fromSet(new HashSet<>()), batch.getLocalWriteTime());
         if (!document.isFoundDocument()) {
           remoteDocuments = remoteDocuments.remove(key);
         }

firebase-firestore/src/main/java/com/google/firebase/firestore/model/ObjectValue.java

@@ -261,7 +261,7 @@ public int hashCode() {
   @Override
   @NonNull
   public String toString() {
-    return "ObjectValue{" + "internalValue=" + buildProto() + '}';
+    return "ObjectValue{" + "internalValue=" + Values.canonicalId(buildProto()) + '}';
   }
 
   @NonNull

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/DeleteMutation.java

@@ -16,6 +16,7 @@
 
 import static com.google.firebase.firestore.util.Assert.hardAssert;
 
+import androidx.annotation.Nullable;
 import com.google.firebase.Timestamp;
 import com.google.firebase.firestore.model.DocumentKey;
 import com.google.firebase.firestore.model.MutableDocument;
@@ -67,11 +68,15 @@ public void applyToRemoteDocument(MutableDocument document, MutationResult mutat
   }
 
   @Override
-  public void applyToLocalView(MutableDocument document, Timestamp localWriteTime) {
+  public @Nullable FieldMask applyToLocalView(
+      MutableDocument document, @Nullable FieldMask previousMask, Timestamp localWriteTime) {
     verifyKeyMatches(document);
 
     if (getPrecondition().isValidFor(document)) {
       document.convertToNoDocument(document.getVersion()).setHasLocalMutations();
+      return null;
     }
+
+    return previousMask;
   }
 }

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/Mutation.java

@@ -16,6 +16,7 @@
 
 import static com.google.firebase.firestore.util.Assert.hardAssert;
 
+import androidx.annotation.Nullable;
 import com.google.firebase.Timestamp;
 import com.google.firebase.firestore.model.Document;
 import com.google.firebase.firestore.model.DocumentKey;
@@ -109,10 +110,13 @@ public abstract void applyToRemoteDocument(
    * modified.
    *
    * @param document The document to mutate.
+   * @param previousMask The fields that have been updated before applying this mutation.
    * @param localWriteTime A timestamp indicating the local write time of the batch this mutation is
    *     a part of.
+   * @return A {@code FieldMask} representing the fields that are changed by applying this mutation.
    */
-  public abstract void applyToLocalView(MutableDocument document, Timestamp localWriteTime);
+  public abstract @Nullable FieldMask applyToLocalView(
+      MutableDocument document, @Nullable FieldMask previousMask, Timestamp localWriteTime);
 
   /** Helper for derived classes to implement .equals(). */
   boolean hasSameKeyAndPrecondition(Mutation other) {
@@ -169,7 +173,7 @@ protected Map<FieldPath, Value> serverTransformResults(
    * result of applying a transform) for use when applying a transform locally.
    *
    * @param localWriteTime The local time of the mutation (used to generate ServerTimestampValues).
-   * @param mutableDocument The current state of the document after applying all previous mutations.
+   * @param mutableDocument The document to apply transforms on.
    * @return A map of fields to transform results.
    */
   protected Map<FieldPath, Value> localTransformResults(

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/MutationBatch.java

@@ -99,22 +99,25 @@ public void applyToRemoteDocument(MutableDocument document, MutationBatchResult
 
   /** Computes the local view of a document given all the mutations in this batch. */
   public void applyToLocalView(MutableDocument document) {
+    FieldMask mutatedFields = FieldMask.fromSet(new HashSet<>());
     // First, apply the base state. This allows us to apply non-idempotent transform against a
     // consistent set of values.
     for (int i = 0; i < baseMutations.size(); i++) {
       Mutation mutation = baseMutations.get(i);
       if (mutation.getKey().equals(document.getKey())) {
-        mutation.applyToLocalView(document, localWriteTime);
+        mutatedFields = mutation.applyToLocalView(document, mutatedFields, localWriteTime);
       }
     }
 
     // Second, apply all user-provided mutations.
     for (int i = 0; i < mutations.size(); i++) {
       Mutation mutation = mutations.get(i);
       if (mutation.getKey().equals(document.getKey())) {
-        mutation.applyToLocalView(document, localWriteTime);
+        mutatedFields = mutation.applyToLocalView(document, mutatedFields, localWriteTime);
       }
     }
+
+    // TODO(Overlay): Calculate overlay mutation here.
   }
 
   /** Computes the local view for all provided documents given the mutations in this batch. */

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/PatchMutation.java

@@ -14,6 +14,7 @@
 
 package com.google.firebase.firestore.model.mutation;
 
+import androidx.annotation.Nullable;
 import com.google.firebase.Timestamp;
 import com.google.firebase.firestore.model.DocumentKey;
 import com.google.firebase.firestore.model.FieldPath;
@@ -22,6 +23,7 @@
 import com.google.firestore.v1.Value;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 
@@ -126,20 +128,39 @@ public void applyToRemoteDocument(MutableDocument document, MutationResult mutat
   }
 
   @Override
-  public void applyToLocalView(MutableDocument document, Timestamp localWriteTime) {
+  public @Nullable FieldMask applyToLocalView(
+      MutableDocument document, @Nullable FieldMask previousMask, Timestamp localWriteTime) {
     verifyKeyMatches(document);
 
     if (!getPrecondition().isValidFor(document)) {
-      return;
+      return previousMask;
     }
 
     Map<FieldPath, Value> transformResults = localTransformResults(localWriteTime, document);
+    Map<FieldPath, Value> patches = getPatch();
     ObjectValue value = document.getData();
-    value.setAll(getPatch());
+    value.setAll(patches);
     value.setAll(transformResults);
     document
         .convertToFoundDocument(document.getVersion(), document.getData())
         .setHasLocalMutations();
+
+    if (previousMask == null) {
+      return null;
+    }
+
+    HashSet<FieldPath> mergedMaskSet = new HashSet<>(previousMask.getMask());
+    mergedMaskSet.addAll(this.mask.getMask());
+    mergedMaskSet.addAll(getFieldTransformPaths());
+    return FieldMask.fromSet(mergedMaskSet);
+  }
+
+  private List<FieldPath> getFieldTransformPaths() {
+    List<FieldPath> result = new ArrayList<>();
+    for (FieldTransform fieldTransform : getFieldTransforms()) {
+      result.add(fieldTransform.getFieldPath());
+    }
+    return result;
   }
 
   private Map<FieldPath, Value> getPatch() {

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/SetMutation.java

@@ -14,6 +14,7 @@
 
 package com.google.firebase.firestore.model.mutation;
 
+import androidx.annotation.Nullable;
 import com.google.firebase.Timestamp;
 import com.google.firebase.firestore.model.DocumentKey;
 import com.google.firebase.firestore.model.FieldPath;
@@ -86,17 +87,20 @@ public void applyToRemoteDocument(MutableDocument document, MutationResult mutat
   }
 
   @Override
-  public void applyToLocalView(MutableDocument document, Timestamp localWriteTime) {
+  public FieldMask applyToLocalView(
+      MutableDocument document, @Nullable FieldMask previousMask, Timestamp localWriteTime) {
     verifyKeyMatches(document);
 
     if (!this.getPrecondition().isValidFor(document)) {
-      return;
+      return previousMask;
     }
 
     Map<FieldPath, Value> transformResults = localTransformResults(localWriteTime, document);
     ObjectValue localValue = value.clone();
     localValue.setAll(transformResults);
     document.convertToFoundDocument(document.getVersion(), localValue).setHasLocalMutations();
+    // SetMutation overwrites all fields.
+    return null;
   }
 
   /** Returns the object value to use when setting the document. */

firebase-firestore/src/main/java/com/google/firebase/firestore/model/mutation/VerifyMutation.java

@@ -14,6 +14,7 @@
 
 package com.google.firebase.firestore.model.mutation;
 
+import androidx.annotation.Nullable;
 import com.google.firebase.Timestamp;
 import com.google.firebase.firestore.model.DocumentKey;
 import com.google.firebase.firestore.model.MutableDocument;
@@ -60,7 +61,9 @@ public void applyToRemoteDocument(MutableDocument document, MutationResult mutat
     throw Assert.fail("VerifyMutation should only be used in Transactions.");
   }
 
-  public void applyToLocalView(MutableDocument document, Timestamp localWriteTime) {
+  @Override
+  public FieldMask applyToLocalView(
+      MutableDocument document, @Nullable FieldMask previousMask, Timestamp localWriteTime) {
     throw Assert.fail("VerifyMutation should only be used in Transactions.");
   }
 }