Fixes for the Codable API (#3734)

* Annotate Transaction and WriteBatch methods as discardable

These methods exist to allow chaining if that's useful but chaining
isn't expected or required.

Note that Objective-C methods in these types are implicitly
@discardableResult and don't need any extra help.

* No need to explicitly discard results

* Fix typos in FIRCollectionReference docs

* Add support for CollectionReference.addDocument(from:)

Author: wilhuff

Firestore/Source/Public/FIRCollectionReference.h

@@ -66,7 +66,7 @@ NS_SWIFT_NAME(CollectionReference)
 - (FIRDocumentReference *)documentWithPath:(NSString *)documentPath NS_SWIFT_NAME(document(_:));
 
 /**
- * Add a new document to this collection with the specified data, assigning it  a document ID
+ * Adds a new document to this collection with the specified data, assigning it a document ID
  * automatically.
  *
  * @param data An `NSDictionary` containing the data for the new document.
@@ -77,7 +77,7 @@ NS_SWIFT_NAME(CollectionReference)
     NS_SWIFT_NAME(addDocument(data:));
 
 /**
- * Add a new document to this collection with the specified data, assigning it a document ID
+ * Adds a new document to this collection with the specified data, assigning it a document ID
  * automatically.
  *
  * @param data An `NSDictionary` containing the data for the new document.

Firestore/Swift/Source/Codable/CollectionReference+WriteEncodable.swift

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import Foundation
+import FirebaseFirestore
+
+extension CollectionReference {
+  /// Encodes an instance of `Encodable` and adds a new document to this collection
+  /// with the encoded data, assigning it a document ID automatically.
+  ///
+  /// See `Firestore.Encoder` for more details about the encoding process.
+  ///
+  /// - Parameters:
+  ///   - value: An instance of `Encodable` to be encoded to a document.
+  ///   - encoder: An encoder instance to use to run the encoding.
+  ///   - completion: A block to execute once the document has been successfully
+  ///                 written to the server. This block will not be called while
+  ///                 the client is offline, though local changes will be visible
+  ///                 immediately.
+  /// - Returns: A `DocumentReference` pointing to the newly created document.
+  public func addDocument<T: Encodable>(from value: T,
+                                        encoder: Firestore.Encoder = Firestore.Encoder(),
+                                        completion: ((Error?) -> Void)? = nil) throws -> DocumentReference {
+    return addDocument(data: try encoder.encode(value), completion: completion)
+  }
+}

Firestore/Swift/Source/Codable/Transaction+WriteEncodable.swift

@@ -29,6 +29,7 @@ extension Transaction {
   ///   - encoder: The encoder instance to use to run the encoding.
   ///   - doc: The document to create/overwrite the encoded data to.
   /// - Returns: This instance of `Transaction`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     encoder: Firestore.Encoder = Firestore.Encoder()) throws -> Transaction {
@@ -50,6 +51,7 @@ extension Transaction {
   ///            document.
   ///   - encoder: The encoder instance to use to run the encoding.
   /// - Returns: This instance of `Transaction`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     merge: Bool,
@@ -76,6 +78,7 @@ extension Transaction {
   ///                  document.
   ///   - encoder: The encoder instance to use to run the encoding.
   /// - Returns: This instance of `Transaction`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     mergeFields: [Any],

Firestore/Swift/Source/Codable/WriteBatch+WriteEncodable.swift

@@ -29,6 +29,7 @@ extension WriteBatch {
   ///   - encoder: The encoder instance to use to run the encoding.
   ///   - doc: The document to create/overwrite the encoded data to.
   /// - Returns: This instance of `WriteBatch`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     encoder: Firestore.Encoder = Firestore.Encoder()) throws -> WriteBatch {
@@ -50,6 +51,7 @@ extension WriteBatch {
   ///            document.
   ///   - encoder: The encoder instance to use to run the encoding.
   /// - Returns: This instance of `WriteBatch`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     merge: Bool,
@@ -76,6 +78,7 @@ extension WriteBatch {
   ///                  document.
   ///   - encoder: The encoder instance to use to run the encoding.
   /// - Returns: This instance of `WriteBatch`. Used for chaining method calls.
+  @discardableResult
   public func setData<T: Encodable>(from value: T,
                                     forDocument doc: DocumentReference,
                                     mergeFields: [Any],

Firestore/Swift/Tests/Integration/CodableIntegrationTests.swift

@@ -55,11 +55,11 @@ class CodableIntegrationTests: FSTIntegrationTestCase {
       doc.firestore.runTransaction({ (transaction, errorPointer) -> Any? in
         do {
           if let merge = merge {
-            _ = try transaction.setData(from: value, forDocument: doc, merge: merge)
+            try transaction.setData(from: value, forDocument: doc, merge: merge)
           } else if let mergeFields = mergeFields {
-            _ = try transaction.setData(from: value, forDocument: doc, mergeFields: mergeFields)
+            try transaction.setData(from: value, forDocument: doc, mergeFields: mergeFields)
           } else {
-            _ = try transaction.setData(from: value, forDocument: doc)
+            try transaction.setData(from: value, forDocument: doc)
           }
         } catch {
           XCTFail("setData with transaction failed.")
@@ -198,4 +198,23 @@ class CodableIntegrationTests: FSTIntegrationTestCase {
                                              age: 10, hobby: "Play"), "Failed with flavor \(flavor)")
     }
   }
+
+  func testAddDocument() throws {
+    struct Model: Codable, Equatable {
+      var name: String
+    }
+
+    let collection = collectionRef()
+    let model = Model(name: "test")
+
+    let added = expectation(description: "Add document")
+    let docRef = try collection.addDocument(from: model) { error in
+      XCTAssertNil(error)
+      added.fulfill()
+    }
+    awaitExpectations()
+
+    let result = try readDocument(forRef: docRef).data(as: Model.self)
+    XCTAssertEqual(model, result)
+  }
 }