Simplify Mutations

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

@@ -216,8 +216,7 @@ public LocalWriteResult writeLocally(List<Mutation> mutations) {
         () -> {
           // Load and apply all existing mutations. This lets us compute the current base state for
           // all non-idempotent transforms before applying any additional user-provided writes.
-          ImmutableSortedMap<DocumentKey, Document> existingDocuments =
-              localDocuments.getDocuments(keys);
+          ImmutableSortedMap<DocumentKey, Document> documents = localDocuments.getDocuments(keys);
 
           // For non-idempotent mutations (such as `FieldValue.increment()`), we record the base
           // state in a separate patch mutation. This is later used to guarantee consistent values
@@ -226,7 +225,7 @@ public LocalWriteResult writeLocally(List<Mutation> mutations) {
           List<Mutation> baseMutations = new ArrayList<>();
           for (Mutation mutation : mutations) {
             ObjectValue baseValue =
-                mutation.extractTransformBaseValue(existingDocuments.get(mutation.getKey()));
+                mutation.extractTransformBaseValue(documents.get(mutation.getKey()));
             if (baseValue != null) {
               // NOTE: The base state should only be applied if there's some existing
               // document to override, so use a Precondition of exists=true
@@ -241,9 +240,8 @@ public LocalWriteResult writeLocally(List<Mutation> mutations) {
 
           MutationBatch batch =
               mutationQueue.addMutationBatch(localWriteTime, baseMutations, mutations);
-          ImmutableSortedMap<DocumentKey, Document> changedDocuments =
-              batch.applyToLocalDocumentSet(existingDocuments);
-          return new LocalWriteResult(batch.getBatchId(), changedDocuments);
+          batch.applyToLocalDocumentSet(documents);
+          return new LocalWriteResult(batch.getBatchId(), documents);
         });
   }
 

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

@@ -43,7 +43,7 @@ private DatabaseId(String projectId, String databaseId) {
   public static DatabaseId fromName(String name) {
     ResourcePath resourceName = ResourcePath.fromString(name);
     hardAssert(
-        resourceName.length() >= 3
+        resourceName.length() > 3
             && resourceName.getSegment(0).equals("projects")
             && resourceName.getSegment(2).equals("databases"),
         "Tried to parse an invalid resource name: %s",

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

@@ -51,7 +51,7 @@ public static DocumentKey empty() {
   public static DocumentKey fromName(String name) {
     ResourcePath resourceName = ResourcePath.fromString(name);
     hardAssert(
-        resourceName.length() >= 4
+        resourceName.length() > 4
             && resourceName.getSegment(0).equals("projects")
             && resourceName.getSegment(2).equals("databases")
             && resourceName.getSegment(4).equals("documents"),

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

@@ -386,12 +386,12 @@ private static void canonifyArray(StringBuilder builder, ArrayValue arrayValue)
     builder.append("]");
   }
 
-  /** Returns true if `value` is either a INTEGER_VALUE. */
+  /** Returns true if `value` is a INTEGER_VALUE. */
   public static boolean isInteger(@Nullable Value value) {
     return value != null && value.getValueTypeCase() == Value.ValueTypeCase.INTEGER_VALUE;
   }
 
-  /** Returns true if `value` is either a DOUBLE_VALUE. */
+  /** Returns true if `value` is a DOUBLE_VALUE. */
   public static boolean isDouble(@Nullable Value value) {
     return value != null && value.getValueTypeCase() == Value.ValueTypeCase.DOUBLE_VALUE;
   }

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

@@ -170,12 +170,7 @@ protected Map<FieldPath, Value> serverTransformResults(
     for (int i = 0; i < serverTransformResults.size(); i++) {
       FieldTransform fieldTransform = fieldTransforms.get(i);
       TransformOperation transform = fieldTransform.getOperation();
-
-      Value previousValue = null;
-      if (mutableDocument.isFoundDocument()) {
-        previousValue = mutableDocument.getField(fieldTransform.getFieldPath());
-      }
-
+      Value previousValue = mutableDocument.getField(fieldTransform.getFieldPath());
       transformResults.put(
           fieldTransform.getFieldPath(),
           transform.applyToRemoteDocument(previousValue, serverTransformResults.get(i)));
@@ -196,12 +191,7 @@ protected Map<FieldPath, Value> localTransformResults(
     Map<FieldPath, Value> transformResults = new HashMap<>(fieldTransforms.size());
     for (FieldTransform fieldTransform : fieldTransforms) {
       TransformOperation transform = fieldTransform.getOperation();
-
-      Value previousValue = null;
-      if (mutableDocument.isFoundDocument()) {
-        previousValue = mutableDocument.getField(fieldTransform.getFieldPath());
-      }
-
+      Value previousValue = mutableDocument.getField(fieldTransform.getFieldPath());
       transformResults.put(
           fieldTransform.getFieldPath(), transform.applyToLocalView(previousValue, localWriteTime));
     }

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

@@ -118,8 +118,7 @@ public void applyToLocalView(MutableDocument document) {
   }
 
   /** Computes the local view for all provided documents given the mutations in this batch. */
-  public ImmutableSortedMap<DocumentKey, Document> applyToLocalDocumentSet(
-      ImmutableSortedMap<DocumentKey, Document> documentMap) {
+  public void applyToLocalDocumentSet(ImmutableSortedMap<DocumentKey, Document> documentMap) {
     // TODO(mrschmidt): This implementation is O(n^2). If we iterate through the mutations first
     // (as done in `applyToLocalView(MutableDocument d)`), we can reduce the complexity to
     // O(n).
@@ -131,9 +130,7 @@ public ImmutableSortedMap<DocumentKey, Document> applyToLocalDocumentSet(
       if (!document.isValidDocument()) {
         document.convertToNoDocument(SnapshotVersion.NONE);
       }
-      documentMap = documentMap.insert(document.getKey(), document);
     }
-    return documentMap;
   }
 
   @Override