Remove FIRAppEnvironmentUtil's sharedApplication (#603)

* Deprecate FIRAppEnvironmentUtil sharedApplication

* Remove sharedApplication private API.

This also allows us to remove an AppKit dependency.

* Disable autolink when building FirebaseCore (#606)

This prevents the dependencies of FirebaseCore's dependencies from
bleeding into its interface.

The proximate benefit of avoiding this is that FirebaseCore no longer
ends up depending on ColorSync.framework which became a top-level system
framework in 10.13. This makes it possible to build against the
resulting FirebaseCore.framework on macOS 10.12 using Xcode 9 (with the
macOS 10.13 SDK).

Author: ryanwilson

Firebase/Core/third_party/FIRAppEnvironmentUtil.h

@@ -16,12 +16,6 @@
 
 #import <Foundation/Foundation.h>
 
-#if TARGET_OS_IOS
-#import <UIKit/UIKit.h>
-#elif TARGET_OS_OSX
-#import <AppKit/AppKit.h>
-#endif
-
 @interface FIRAppEnvironmentUtil : NSObject
 
 /// Indicates whether the app is from Apple Store or not. Returns NO if the app is on simulator,
@@ -46,12 +40,4 @@
 /// Indicates whether it is running inside an extension or an app.
 + (BOOL)isAppExtension;
 
-#if TARGET_OS_IOS
-/// Returns the [UIApplication sharedApplication] if it is running on an app, not an extension.
-+ (UIApplication *)sharedApplication;
-#elif TARGET_OS_OSX
-/// Returns the [NSApplication sharedApplication].
-+ (NSApplication *)sharedApplication;
-#endif
-
 @end

Firebase/Core/third_party/FIRAppEnvironmentUtil.m

@@ -13,6 +13,9 @@
 // limitations under the License.
 
 #import <Foundation/Foundation.h>
+#if TARGET_OS_IOS || TARGET_OS_TV
+#import <UIKit/UIKit.h>
+#endif
 
 #import "FIRAppEnvironmentUtil.h"
 
@@ -221,25 +224,6 @@ + (BOOL)isAppExtension {
   #endif
 }
 
-#if TARGET_OS_IOS
-+ (UIApplication *)sharedApplication {
-  if ([FIRAppEnvironmentUtil isAppExtension]) {
-    return nil;
-  }
-  id sharedApplication = nil;
-  Class uiApplicationClass = NSClassFromString(@"UIApplication");
-  if (uiApplicationClass &&
-      [uiApplicationClass respondsToSelector:(NSSelectorFromString(@"sharedApplication"))]) {
-    sharedApplication = [uiApplicationClass sharedApplication];
-  }
-  return sharedApplication;
-}
-#elif TARGET_OS_OSX
-+ (NSApplication *)sharedApplication {
-  return [NSApplication sharedApplication];
-}
-#endif
-
 #pragma mark - Helper methods
 
 + (BOOL)hasSCInfoFolder {

FirebaseCore.podspec

@@ -26,9 +26,13 @@ Firebase Core includes FIRApp and FIROptions which provide central configuration
   s.source_files = 'Firebase/Core/**/*.[mh]'
   s.public_header_files = 'Firebase/Core/Public/*.h', 'Firebase/Core/Private/*.h'
   s.private_header_files = 'Firebase/Core/Private/*.h'
-  s.framework = 'SystemConfiguration'
+  s.frameworks = [
+    'Foundation',
+    'SystemConfiguration'
+  ]
   s.dependency 'GoogleToolboxForMac/NSData+zlib', '~> 2.1'
   s.pod_target_xcconfig = {
-    'OTHER_CFLAGS' => '-DFIRCore_VERSION=' + s.version.to_s + ' -DFirebase_VERSION=4.8.0'
+    'OTHER_CFLAGS' => '-fno-autolink ' +
+      '-DFIRCore_VERSION=' + s.version.to_s + ' -DFirebase_VERSION=4.8.0'
   }
 end

cmake/FindFirebaseCore.cmake

@@ -33,11 +33,10 @@ if(FIREBASECORE_FOUND)
     ${FIREBASECORE_LIBRARY}/PrivateHeaders
   )
 
-  # TODO(mcg): on iOS this should depend on UIKit.
   set(
     FIREBASECORE_LIBRARIES
     ${FIREBASECORE_LIBRARY}
-    "-framework AppKit"
+    "-framework Foundation"
   )
 
   if(NOT TARGET FirebaseCore)