WIP: last check all pass

Author: Brian Chen

Firestore/core/src/local/local_serializer.cc

@@ -48,6 +48,7 @@ namespace {
 using core::Target;
 using model::Document;
 using model::DocumentState;
+using model::FieldTransform;
 using model::FieldValue;
 using model::MaybeDocument;
 using model::Mutation;
@@ -328,11 +329,47 @@ MutationBatch LocalSerializer::DecodeMutationBatch(
   }
 
   std::vector<Mutation> mutations;
-  for (size_t i = 0; i < proto.writes_count; i++) {
-    mutations.push_back(
-        rpc_serializer_.DecodeMutation(reader, proto.writes[i]));
+
+  // Squash old transform mutations into existing patch of set mutations. The
+  // replacement of representing `transforms` with `update_transforms` on the
+  // SDK means that old `transform` mutations stored in LevelDB need to be
+  // updated to `update_transforms`.
+  // TODO(b/174608374): Remove this code once we perform a schema migration.
+  for (size_t i = proto.writes_count - 1; i >= 0; --i) {
+    _google_firestore_v1_Write mutation = proto.writes[i];
+    if (mutation.which_operation == google_firestore_v1_Write_transform_tag) {
+      HARD_ASSERT(
+          i >= 1 && proto.writes[i - 1].which_operation ==
+                        google_firestore_v1_Write_update_tag,
+          "TransformMutation should be preceded by a patch or set mutation");
+      _google_firestore_v1_Write mutation_to_join = proto.writes[i - 1];
+      _google_firestore_v1_Write new_mutation{mutation_to_join};
+      new_mutation.update_transforms_count =
+          mutation.transform.field_transforms_count;
+      new_mutation.update_transforms =
+          MakeArray<_google_firestore_v1_DocumentTransform_FieldTransform>(
+              mutation.transform.field_transforms_count);
+      for (size_t j = 0; j < mutation.transform.field_transforms_count; ++j) {
+        new_mutation.update_transforms[j] =
+            mutation.transform.field_transforms[j];
+      }
+      mutations.push_back(rpc_serializer_.DecodeMutation(reader, new_mutation));
+      --i;
+    } else {
+      mutations.push_back(rpc_serializer_.DecodeMutation(reader, mutation));
+    }
+
+    // TODO: figure out how to exit the loop without size_t looping around
+    if (i == 0) {
+      break;
+    }
   }
 
+  // Reverse the mutations to preserve the original ordering since the above
+  // for-loop iterates in reverse order. We use reverse() instead of prepending
+  // the elements into the mutations array since prepending to a List is O(n).
+  std::reverse(mutations.begin(), mutations.end());
+
   return MutationBatch(batch_id, local_write_time, std::move(base_mutations),
                        std::move(mutations));
 }

Firestore/core/src/remote/serializer.cc

@@ -591,11 +591,9 @@ google_firestore_v1_Write Serializer::EncodeMutation(
   result.update_transforms =
       MakeArray<google_firestore_v1_DocumentTransform_FieldTransform>(count);
   int i = 0;
-  auto crazy = mutation.field_transforms();
-  auto crazy2 = mutation.key();
   for (const FieldTransform& field_transform : mutation.field_transforms()) {
     result.update_transforms[i] = EncodeFieldTransform(field_transform);
-    i++;
+    ++i;
   }
 
   switch (mutation.type()) {