Adding more logs around mutations and acks

Firestore/Swift/Tests/Integration/QueryIntegrationTests.swift

@@ -166,6 +166,17 @@ class QueryIntegrationTests: FSTIntegrationTestCase {
       matchesResult: ["doc2"])
   }
 
+  func testFailedWriteBatch() throws {
+    let batch = db.batch()
+      .updateData(["a": 1, "b": 0], forDocument: documentRef())
+    let a = expectation(description: "wait for mutation")
+    batch.commit { [weak self] err in
+      XCTAssert(err != nil)
+      a.fulfill()
+    }
+    awaitExpectation(a)
+  }
+
   func testOrQueriesWithIn() throws {
     let collRef = collectionRef(
       withDocuments: ["doc1": ["a": 1, "b": 0],

Firestore/core/src/core/firestore_client.cc

@@ -523,13 +523,17 @@ void FirestoreClient::WriteMutations(std::vector<Mutation>&& mutations,
     if (mutations.empty()) {
       if (callback) {
         user_executor_->Execute([=] { callback(Status::OK()); });
+      } else {
+        LOG_WARN("Skipping callback due to empty mutations");
       }
     } else {
       sync_engine_->WriteMutations(
           std::move(mutations), [this, callback](Status error) {
             // Dispatch the result back onto the user dispatch queue.
             if (callback) {
               user_executor_->Execute([=] { callback(std::move(error)); });
+            } else {
+              LOG_WARN("Skipping callback due to null call back");
             }
           });
     }

Firestore/core/src/core/sync_engine.cc

@@ -408,9 +408,9 @@ void SyncEngine::HandleRejectedWrite(
 
   DocumentMap changes = local_store_->RejectBatch(batch_id);
 
-  if (!changes.empty() && ErrorIsInteresting(error)) {
+  if (!changes.empty()) {
     const DocumentKey& min_key = changes.min()->first;
-    LOG_WARN("Write at %s failed: %s", min_key.ToString(),
+    LOG_WARN("Write batch %s at %s failed: %s", batch_id, min_key.ToString(),
              error.error_message());
   }
 
@@ -469,6 +469,10 @@ void SyncEngine::NotifyUser(BatchId batch_id, Status status) {
   // NOTE: Mutations restored from persistence won't have callbacks, so
   // it's okay for this (or the callback below) to not exist.
   if (it == mutation_callbacks_.end()) {
+    if (!status.ok()) {
+      LOG_WARN("Could not find mutation callback queue for user %s",
+               current_user_.uid());
+    }
     return;
   }
 
@@ -477,6 +481,9 @@ void SyncEngine::NotifyUser(BatchId batch_id, Status status) {
   if (callback_it != callbacks.end()) {
     callback_it->second(std::move(status));
     callbacks.erase(callback_it);
+  } else if (!status.ok()) {
+    LOG_WARN("Could not find mutation callback for user %s and batch %s",
+             current_user_.uid(), batch_id);
   }
 }