Revisit commit method in FIRWriteBatch (#541)

* revisit FIRWriteBatch commit

*   make commitWithCompletion completion nullable;
*   add commit;
*   add unit test;
*   add swift build test for commit;
*   update CHANGELOG.

5 files changed, 55 insertions, 2 deletions

diff --git a/Firestore/CHANGELOG.md b/Firestore/CHANGELOG.md
index 32cbbfc..1a8eb07 100644
--- a/Firestore/CHANGELOG.md
+++ b/Firestore/CHANGELOG.md
@@ -2,6 +2,7 @@
 - [changed] Firestore no longer has a direct dependency on FirebaseAuth.
 - [changed] Removed the includeMetadataChanges property in FIRDocumentListenOptions
   to avoid confusion with the factory method of the same name.
+- [changed] Added a commit method that takes no completion handler to FIRWriteBatch.
 - [fixed] Fixed a crash when using path names with international characters
   with persistence enabled.
 
diff --git a/Firestore/Example/SwiftBuildTest/main.swift b/Firestore/Example/SwiftBuildTest/main.swift
index bea8b56..475c1b2 100644
--- a/Firestore/Example/SwiftBuildTest/main.swift
+++ b/Firestore/Example/SwiftBuildTest/main.swift
@@ -27,6 +27,8 @@ func main() {
 
     writeDocument(at: documentRef);
 
+    writeDocuments(at: documentRef, database: db);
+
     addDocument(to: collectionRef);
 
     readDocument(at: documentRef);
@@ -129,6 +131,30 @@ func writeDocument(at docRef: DocumentReference) {
     }
 }
 
+func writeDocuments(at docRef: DocumentReference, database db: Firestore) {
+  var batch: WriteBatch;
+
+  batch = db.batch();
+  batch.setData(["a" : "b"], forDocument:docRef);
+  batch.setData(["c" : "d"], forDocument:docRef);
+  // commit without completion callback.
+  batch.commit();
+  print("Batch write without completion complete!");
+
+  batch = db.batch();
+  batch.setData(["a" : "b"], forDocument:docRef);
+  batch.setData(["c" : "d"], forDocument:docRef);
+  // commit with completion callback via trailing closure syntax.
+  batch.commit() { error in
+    if let error = error {
+      print("Uh oh! \(error)");
+      return;
+    }
+    print("Batch write callback complete!");
+  }
+  print("Batch write with completion complete!");
+}
+
 func addDocument(to collectionRef: CollectionReference) {
 
     collectionRef.addDocument(data: ["foo": 42]);
diff --git a/Firestore/Example/Tests/Integration/API/FIRWriteBatchTests.m b/Firestore/Example/Tests/Integration/API/FIRWriteBatchTests.m
index 562c29f..23ae7bc 100644
--- a/Firestore/Example/Tests/Integration/API/FIRWriteBatchTests.m
+++ b/Firestore/Example/Tests/Integration/API/FIRWriteBatchTests.m
@@ -35,6 +35,23 @@
   [self awaitExpectations];
 }
 
+- (void)testCommitWithoutCompletionHandler {
+  FIRDocumentReference *doc = [self documentRef];
+  FIRWriteBatch *batch1 = [doc.firestore batch];
+  [batch1 setData:@{@"aa" : @"bb"} forDocument:doc];
+  [batch1 commitWithCompletion:nil];
+  FIRDocumentSnapshot *snapshot1 = [self readDocumentForRef:doc];
+  XCTAssertTrue(snapshot1.exists);
+  XCTAssertEqualObjects(snapshot1.data, @{@"aa" : @"bb"});
+
+  FIRWriteBatch *batch2 = [doc.firestore batch];
+  [batch2 setData:@{@"cc" : @"dd"} forDocument:doc];
+  [batch2 commit];
+  FIRDocumentSnapshot *snapshot2 = [self readDocumentForRef:doc];
+  XCTAssertTrue(snapshot2.exists);
+  XCTAssertEqualObjects(snapshot2.data, @{@"cc" : @"dd"});
+}
+
 - (void)testSetDocuments {
   FIRDocumentReference *doc = [self documentRef];
   XCTestExpectation *batchExpectation = [self expectationWithDescription:@"batch written"];
diff --git a/Firestore/Source/API/FIRWriteBatch.m b/Firestore/Source/API/FIRWriteBatch.m
index b918a9a..b1cfa09 100644
--- a/Firestore/Source/API/FIRWriteBatch.m
+++ b/Firestore/Source/API/FIRWriteBatch.m
@@ -93,7 +93,11 @@ NS_ASSUME_NONNULL_BEGIN
   return self;
 }
 
-- (void)commitWithCompletion:(void (^)(NSError *_Nullable error))completion {
+- (void)commit {
+  [self commitWithCompletion:nil];
+}
+
+- (void)commitWithCompletion:(nullable void (^)(NSError *_Nullable error))completion {
   [self verifyNotCommitted];
   self.committed = TRUE;
   [self.firestore.client writeMutations:self.mutations completion:completion];
diff --git a/Firestore/Source/Public/FIRWriteBatch.h b/Firestore/Source/Public/FIRWriteBatch.h
index 5f0034c..8ff1bec 100644
--- a/Firestore/Source/Public/FIRWriteBatch.h
+++ b/Firestore/Source/Public/FIRWriteBatch.h
@@ -94,6 +94,11 @@ NS_SWIFT_NAME(WriteBatch)
 
 /**
  * Commits all of the writes in this write batch as a single atomic unit.
+ */
+- (void)commit;
+
+/**
+ * Commits all of the writes in this write batch as a single atomic unit.
  *
  * @param completion A block to be called once all of the writes in the batch have been
  *     successfully written to the backend as an atomic unit. This block will only execute
@@ -101,7 +106,7 @@ NS_SWIFT_NAME(WriteBatch)
  *     completion handler will not be called when the device is offline, though local
  *     changes will be visible immediately.
  */
-- (void)commitWithCompletion:(void (^)(NSError *_Nullable error))completion;
+- (void)commitWithCompletion:(nullable void (^)(NSError *_Nullable error))completion;
 
 @end