FIRApp: add apple platform to firebaseUserAgent (#4939)

* FIRAppTests: apple platform flag

* FIRApp: add apple platform to firebaseUserAgent

* Make sure Catalyst app run on macOS is logged as "maccatalyst"

* Comments

Author: maksymmalyhin

FirebaseCore/Sources/FIRApp.m

@@ -78,6 +78,7 @@
 NSString *const kFIRAppDiagnosticsFIRAppKey = @"FIRApp";
 NSString *const kFIRAppDiagnosticsSDKNameKey = @"SDKName";
 NSString *const kFIRAppDiagnosticsSDKVersionKey = @"SDKVersion";
+NSString *const kFIRAppDiagnosticsApplePlatformPrefix = @"apple-platform";
 
 // Auth internal notification notification and key.
 NSString *const FIRAuthStateDidChangeInternalNotification =
@@ -579,6 +580,9 @@ + (NSString *)firebaseUserAgent {
 
       NSString *swiftFlagValue = [self hasSwiftRuntime] ? @"true" : @"false";
       [FIRApp registerLibrary:@"swift" withVersion:swiftFlagValue];
+
+      [FIRApp registerLibrary:kFIRAppDiagnosticsApplePlatformPrefix
+                  withVersion:[self applePlatform]];
     });
 
     NSMutableArray<NSString *> *libraries =
@@ -606,6 +610,26 @@ + (BOOL)hasSwiftRuntime {
   return hasSwiftRuntime;
 }
 
++ (NSString *)applePlatform {
+  NSString *applePlatform = @"unknown";
+
+  // When a Catalyst app is run on macOS then both `TARGET_OS_MACCATALYST` and `TARGET_OS_IOS` are
+  // `true`, which means the condition list is order-sensitive.
+#if TARGET_OS_MACCATALYST
+  applePlatform = @"maccatalyst";
+#elif TARGET_OS_IOS
+  applePlatform = @"ios";
+#elif TARGET_OS_TV
+  applePlatform = @"tvos";
+#elif TARGET_OS_OSX
+  applePlatform = @"macos";
+#elif TARGET_OS_WATCH
+  applePlatform = @"watchos";
+#endif
+
+  return applePlatform;
+}
+
 - (void)checkExpectedBundleID {
   NSArray *bundles = [FIRBundleUtil relevantBundles];
   NSString *expectedBundleID = [self expectedBundleID];

FirebaseCore/Tests/Unit/FIRAppTest.m

@@ -838,6 +838,48 @@ - (void)testSwiftFlagWithNoSwift {
   XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"swift/false"]);
 }
 
+- (void)testApplePlatformFlag {
+  // When a Catalyst app is run on macOS then both `TARGET_OS_MACCATALYST` and `TARGET_OS_IOS` are
+  // `true`.
+#if TARGET_OS_MACCATALYST
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/ios"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/tvos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/macos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/watchos"]);
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"apple-platform/maccatalyst"]);
+#elif TARGET_OS_IOS
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"apple-platform/ios"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/tvos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/macos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/watchos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/maccatalyst"]);
+#endif  // TARGET_OS_MACCATALYST
+
+#if TARGET_OS_TV
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/ios"]);
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"apple-platform/tvos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/macos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/watchos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/maccatalyst"]);
+#endif  // TARGET_OS_TV
+
+#if TARGET_OS_OSX
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/ios"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/tvos"]);
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"apple-platform/macos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/watchos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/maccatalyst"]);
+#endif  // TARGET_OS_OSX
+
+#if TARGET_OS_WATCH
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/ios"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/tvos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/macos"]);
+  XCTAssertTrue([[FIRApp firebaseUserAgent] containsString:@"apple-platform/watchos"]);
+  XCTAssertFalse([[FIRApp firebaseUserAgent] containsString:@"apple-platform/maccatalyst"]);
+#endif  // TARGET_OS_WATCH
+}
+
 #pragma mark - Core Diagnostics
 
 - (void)testCoreDiagnosticsLoggedWhenFIRAppIsConfigured {