Fix GoogleUtilities warnings in static library installs (#1830)

.travis.yml

@@ -80,9 +80,6 @@ jobs:
       before_install:
         - ./scripts/if_cron.sh ./scripts/install_prereqs.sh
       script:
-        # For GoogleUtilities, allow warnings for iOS 6 but not iOS 7.
-        - ./scripts/if_cron.sh ./scripts/pod_lib_lint.sh GoogleUtilities.podspec --use-libraries --allow-warnings
-        - ./scripts/if_cron.sh sed -i -e "s/s.ios.deployment_target = '6.0'/s.ios.deployment_target = '7.0'/" GoogleUtilities.podspec
         - ./scripts/if_cron.sh ./scripts/pod_lib_lint.sh GoogleUtilities.podspec --use-libraries
         - ./scripts/if_cron.sh ./scripts/pod_lib_lint.sh FirebaseCore.podspec --use-libraries
         - ./scripts/if_cron.sh ./scripts/pod_lib_lint.sh FirebaseAuth.podspec --use-libraries

GoogleUtilities.podspec

@@ -16,6 +16,8 @@ other Google CocoaPods. They're not intended for direct public usage.
     :git => 'https://github.com/firebase/firebase-ios-sdk.git',
     :tag => 'Utilities-' + s.version.to_s
   }
+  # Technically GoogleUtilites requires iOS 7, but it supports a dependency pod with a minimum
+  # iOS 6, that will do runtime checking to avoid calling into GoogleUtilities.
   s.ios.deployment_target = '6.0'
   s.osx.deployment_target = '10.10'
   s.tvos.deployment_target = '10.0'

GoogleUtilities/AppDelegateSwizzler/GULAppDelegateSwizzler.m

@@ -594,7 +594,7 @@ static dispatch_once_t sProxyAppDelegateOnceToken;
 #pragma clang diagnostic ignored "-Wstrict-prototypes"
 - (void)application:(UIApplication *)application
     handleEventsForBackgroundURLSession:(NSString *)identifier
-                      completionHandler:(void (^)())completionHandler {
+                      completionHandler:(void (^)())completionHandler API_AVAILABLE(ios(7.0)) {
 #pragma clang diagnostic pop
   NSValue *handleBackgroundSessionPointer =
       objc_getAssociatedObject(self, &kGULHandleBackgroundSessionIMPKey);

GoogleUtilities/Environment/third_party/GULAppEnvironmentUtil.m

@@ -187,10 +187,17 @@ static BOOL HasEmbeddedMobileProvision() {
       ![enableSandboxCheck boolValue]) {
     return NO;
   }
-
-  NSURL *appStoreReceiptURL = [NSBundle mainBundle].appStoreReceiptURL;
-  NSString *appStoreReceiptFileName = appStoreReceiptURL.lastPathComponent;
-  return [appStoreReceiptFileName isEqualToString:kFIRAIdentitySandboxReceiptFileName];
+// The #else is for pre Xcode 9 where @available is not yet implemented.
+#if __has_builtin(__builtin_available)
+  if (@available(iOS 7.0, *)) {
+#else
+  if ([[UIDevice currentDevice].systemVersion integerValue] >= 7) {
+#endif
+    NSURL *appStoreReceiptURL = [NSBundle mainBundle].appStoreReceiptURL;
+    NSString *appStoreReceiptFileName = appStoreReceiptURL.lastPathComponent;
+    return [appStoreReceiptFileName isEqualToString:kFIRAIdentitySandboxReceiptFileName];
+  }
+  return NO;
 }
 
 + (BOOL)isSimulator {

GoogleUtilities/Network/GULNetworkURLSession.m

@@ -28,8 +28,11 @@
   /// Session ID generated randomly with a fixed prefix.
   NSString *_sessionID;
 
-  /// The session configuration.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunguarded-availability"
+  /// The session configuration. NSURLSessionConfiguration' is only available on iOS 7.0 or newer.
   NSURLSessionConfiguration *_sessionConfig;
+#pragma pop
 
   /// The path to the directory where all temporary files are stored before uploading.
   NSURL *_networkDirectoryURL;
@@ -92,7 +95,8 @@
 /// Sends an async POST request using NSURLSession for iOS >= 7.0, and returns an ID of the
 /// connection.
 - (NSString *)sessionIDFromAsyncPOSTRequest:(NSURLRequest *)request
-                          completionHandler:(GULNetworkURLSessionCompletionHandler)handler {
+                          completionHandler:(GULNetworkURLSessionCompletionHandler)handler
+    API_AVAILABLE(ios(7.0)) {
   // NSURLSessionUploadTask does not work with NSData in the background.
   // To avoid this issue, write the data to a temporary file to upload it.
   // Make a temporary file with the data subset.
@@ -169,7 +173,8 @@
 
 /// Sends an async GET request using NSURLSession for iOS >= 7.0, and returns an ID of the session.
 - (NSString *)sessionIDFromAsyncGETRequest:(NSURLRequest *)request
-                         completionHandler:(GULNetworkURLSessionCompletionHandler)handler {
+                         completionHandler:(GULNetworkURLSessionCompletionHandler)handler
+    API_AVAILABLE(ios(7.0)) {
   if (_backgroundNetworkEnabled) {
     _sessionConfig = [self backgroundSessionConfigWithSessionID:_sessionID];
   } else {
@@ -215,7 +220,7 @@
 /// be called with the downloaded data.
 - (void)URLSession:(NSURLSession *)session
                  downloadTask:(NSURLSessionDownloadTask *)task
-    didFinishDownloadingToURL:(NSURL *)url {
+    didFinishDownloadingToURL:(NSURL *)url API_AVAILABLE(ios(7.0)) {
   if (!url.path) {
     [_loggerDelegate
         GULNetwork_logWithLevel:kGULNetworkLogLevelError
@@ -238,7 +243,8 @@
 }
 
 #if TARGET_OS_IOS || TARGET_OS_TV
-- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session {
+- (void)URLSessionDidFinishEventsForBackgroundURLSession:(NSURLSession *)session
+    API_AVAILABLE(ios(7.0)) {
   [_loggerDelegate GULNetwork_logWithLevel:kGULNetworkLogLevelDebug
                                messageCode:kGULNetworkMessageCodeURLSession003
                                    message:@"Background session finished"
@@ -249,7 +255,7 @@
 
 - (void)URLSession:(NSURLSession *)session
                     task:(NSURLSessionTask *)task
-    didCompleteWithError:(NSError *)error {
+    didCompleteWithError:(NSError *)error API_AVAILABLE(ios(7.0)) {
   // Avoid any chance of recursive behavior leading to it being used repeatedly.
   GULNetworkURLSessionCompletionHandler handler = _completionHandler;
   _completionHandler = nil;
@@ -284,7 +290,8 @@
                    task:(NSURLSessionTask *)task
     didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge
       completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition,
-                                  NSURLCredential *credential))completionHandler {
+                                  NSURLCredential *credential))completionHandler
+    API_AVAILABLE(ios(7.0)) {
   // The handling is modeled after GTMSessionFetcher.
   if ([challenge.protectionSpace.authenticationMethod
           isEqualToString:NSURLAuthenticationMethodServerTrust]) {
@@ -427,7 +434,8 @@
 }
 
 /// Creates a background session configuration with the session ID using the supported method.
-- (NSURLSessionConfiguration *)backgroundSessionConfigWithSessionID:(NSString *)sessionID {
+- (NSURLSessionConfiguration *)backgroundSessionConfigWithSessionID:(NSString *)sessionID
+    API_AVAILABLE(ios(7.0)) {
 #if (TARGET_OS_OSX && defined(MAC_OS_X_VERSION_10_10) &&         \
      MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_X_VERSION_10_10) || \
     TARGET_OS_TV ||                                              \
@@ -619,7 +627,7 @@
                           task:(NSURLSessionTask *)task
     willPerformHTTPRedirection:(NSHTTPURLResponse *)response
                     newRequest:(NSURLRequest *)request
-             completionHandler:(void (^)(NSURLRequest *))completionHandler {
+             completionHandler:(void (^)(NSURLRequest *))completionHandler API_AVAILABLE(ios(7.0)) {
   NSArray *nonAllowedRedirectionCodes = @[
     @(kGULNetworkHTTPStatusCodeFound), @(kGULNetworkHTTPStatusCodeMovedPermanently),
     @(kGULNetworkHTTPStatusCodeMovedTemporarily), @(kGULNetworkHTTPStatusCodeMultipleChoices)
@@ -662,7 +670,7 @@
 }
 
 - (void)populateSessionConfig:(NSURLSessionConfiguration *)sessionConfig
-                  withRequest:(NSURLRequest *)request {
+                  withRequest:(NSURLRequest *)request API_AVAILABLE(ios(7.0)) {
   sessionConfig.HTTPAdditionalHeaders = request.allHTTPHeaderFields;
   sessionConfig.timeoutIntervalForRequest = request.timeoutInterval;
   sessionConfig.timeoutIntervalForResource = request.timeoutInterval;