Add "swift" flag to firebaseUserAgent

Example/Core/Tests/FIRAppTest.m

@@ -784,8 +784,9 @@ - (void)testInvalidLibraryName {
 }
 
 - (void)testInvalidLibraryVersion {
+  NSString *originalFirebaseUserAgent = [FIRApp firebaseUserAgent];
   [FIRApp registerLibrary:@"ValidName" withVersion:@"1.0.0+"];
-  XCTAssertTrue([[FIRApp firebaseUserAgent] isEqualToString:@""]);
+  XCTAssertTrue([[FIRApp firebaseUserAgent] isEqualToString:originalFirebaseUserAgent]);
 }
 
 - (void)testSingleLibrary {
@@ -812,6 +813,10 @@ - (void)testRegisteringNonConformingLibrary {
   XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"InvalidLibrary`/1.0.0"]);
 }
 
+- (void)testSwiftFlagWithNoSwift {
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"swift/false"]);
+}
+
 #pragma mark - Core Diagnostics
 
 - (void)testCoreDiagnosticsLoggedWhenFIRAppIsConfigured {

Example/Core/Tests/Swift/FIRAppTests.swift

@@ -0,0 +1,22 @@
+// Copyright 2019 Google
+//
+// 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 XCTest
+@testable import FirebaseCore
+
+class FIRAppTests: XCTestCase {
+  func testSwiftFlagWithSwift() {
+    XCTAssertTrue(FirebaseApp.firebaseUserAgent().contains("swift"))
+  }
+}

Example/Core/Tests/Swift/FirebaseCore-iOS-Unit-swift-unit-Bridging-Header.h

@@ -0,0 +1,15 @@
+// Copyright 2019 Google
+//
+// 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 "FIRAppInternal.h"

Firebase/Core/FIRApp.m

@@ -37,6 +37,8 @@
 
 #import <GoogleUtilities/GULAppEnvironmentUtil.h>
 
+#import <objc/runtime.h>
+
 // The kFIRService strings are only here while transitioning CoreDiagnostics from the Analytics
 // pod to a Core dependency. These symbols are not used and should be deleted after the transition.
 NSString *const kFIRServiceAdMob;
@@ -114,6 +116,7 @@ @implementation FIRApp
 static NSMutableDictionary *sAllApps;
 static FIRApp *sDefaultApp;
 static NSMutableDictionary *sLibraryVersions;
+static dispatch_once_t sFirebaseUserAgentOnceToken;
 
 + (void)configure {
   FIROptions *options = [FIROptions defaultOptions];
@@ -275,6 +278,7 @@ + (void)resetApps {
     sAllApps = nil;
     [sLibraryVersions removeAllObjects];
     sLibraryVersions = nil;
+    sFirebaseUserAgentOnceToken = 0;
   }
 }
 
@@ -556,8 +560,7 @@ + (void)registerInternalLibrary:(nonnull Class<FIRLibrary>)library
 
 + (NSString *)firebaseUserAgent {
   @synchronized(self) {
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
+    dispatch_once(&sFirebaseUserAgentOnceToken, ^{
       // Report FirebaseCore version for useragent string
       [FIRApp registerLibrary:@"fire-ios"
                   withVersion:[NSString stringWithUTF8String:FIRCoreVersionString]];
@@ -571,7 +574,11 @@ + (NSString *)firebaseUserAgent {
       if (sdkVersion) {
         [FIRApp registerLibrary:@"apple-sdk" withVersion:sdkVersion];
       }
+
+      NSString *swiftFlagValue = [self hasSwiftRuntime] ? @"true" : @"false";
+      [FIRApp registerLibrary:@"swift" withVersion:swiftFlagValue];
     });
+
     NSMutableArray<NSString *> *libraries =
         [[NSMutableArray<NSString *> alloc] initWithCapacity:sLibraryVersions.count];
     for (NSString *libraryName in sLibraryVersions) {
@@ -583,6 +590,20 @@ + (NSString *)firebaseUserAgent {
   }
 }
 
++ (BOOL)hasSwiftRuntime {
+  // The class
+  // [Swift._SwiftObject](https://github.com/apple/swift/blob/5eac3e2818eb340b11232aff83edfbd1c307fa03/stdlib/public/runtime/SwiftObject.h#L35)
+  // is a part of Swift runtime, so it should be present if Swift runtime is available.
+
+  BOOL hasSwiftRuntime =
+      objc_lookUpClass("Swift._SwiftObject") != nil ||
+      // Swift object class name before
+      // https://github.com/apple/swift/commit/9637b4a6e11ddca72f5f6dbe528efc7c92f14d01
+      objc_getClass("_TtCs12_SwiftObject") != nil;
+
+  return hasSwiftRuntime;
+}
+
 - (void)checkExpectedBundleID {
   NSArray *bundles = [FIRBundleUtil relevantBundles];
   NSString *expectedBundleID = [self expectedBundleID];

FirebaseCore.podspec

@@ -48,4 +48,12 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
     unit_tests.dependency 'OCMock'
     unit_tests.resources = 'Example/Core/App/GoogleService-Info.plist'
   end
+
+  s.test_spec 'swift-unit' do |swift_unit_tests|
+    swift_unit_tests.source_files = 'Example/Core/Tests/Swift/**/*.swift',
+                                    'Example/Core/Tests/Swift/**/*.h'
+    swift_unit_tests.pod_target_xcconfig = {
+      'SWIFT_OBJC_BRIDGING_HEADER' => '$(PODS_TARGET_SRCROOT)/Example/Core/Tests/Swift/FirebaseCore-iOS-Unit-swift-unit-Bridging-Header.h'
+    }
+  end
 end