Add Auth interoperability library. (#1501)

* Add Auth interoperability library.

This allows other SDKs to retrieve the user ID and fetch a new
Auth token in a type-safe way through the Core container.

* Remove unnecessary import.

* Add missing copyright.

* Resolve comments.

- Remove unnecessary umbrella header.
- Move to version 1.0.
- Add tvOS support for app lifecycle changes.

* Move public interop headers to private.

* Add public_header_files too.

* Moved headers back into public.

* Shorten Interoperability and Interoperable to Interop.

* Add AuthInterop to travis linting.

* Fixed tag format in AuthInterop.podspec.

* Add AuthInterop path to Firestore Podfile.

3 files changed, 27 insertions, 0 deletions

diff --git a/Example/Auth/Tests/FIRAuthTests.m b/Example/Auth/Tests/FIRAuthTests.m
index 6a047a4..c008bab 100644
--- a/Example/Auth/Tests/FIRAuthTests.m
+++ b/Example/Auth/Tests/FIRAuthTests.m
@@ -18,7 +18,11 @@
 
 #import <XCTest/XCTest.h>
 
+#import <FirebaseAuth/FirebaseAuth.h>
+#import <FirebaseAuthInterop/FIRAuthInterop.h>
 #import <FirebaseCore/FIRAppInternal.h>
+#import <FirebaseCore/FIRComponent.h>
+#import <FirebaseCore/FIRComponentRegistrant.h>
 
 #import "FIRAdditionalUserInfo.h"
 #import "FIRAuth_Internal.h"
@@ -221,6 +225,10 @@ static const NSTimeInterval kExpectationTimeout = 2;
  */
 static const NSTimeInterval kWaitInterval = .5;
 
+/** Category for FIRAuth to expose FIRComponentRegistrant conformance. */
+@interface FIRAuth () <FIRComponentRegistrant>
+@end
+
 /** @class FIRAuthTests
     @brief Tests for @c FIRAuth.
  */
@@ -362,6 +370,8 @@ static const NSTimeInterval kWaitInterval = .5;
     @brief Verifies that FIRApp's getUIDImplementation is correctly set by FIRAuth.
  */
 - (void)testGetUID {
+  // TODO: Remove this test once Firestore, Database, and Storage move over to the new Auth interop
+  //       library.
   FIRApp *app = [FIRApp defaultApp];
   XCTAssertNotNil(app.getUIDImplementation);
   [[FIRAuth auth] signOut:NULL];
@@ -2221,6 +2231,21 @@ static const NSTimeInterval kWaitInterval = .5;
 }
 #endif
 
+#pragma mark - Interoperability Tests
+
+/** @fn testComponentsBeingRegistered
+ @brief Tests that Auth provides the necessary components for interoperability with other SDKs.
+ */
+- (void)testComponentsBeingRegistered {
+  // Verify that the components are registered properly. Check the count, because any time a new
+  // component is added it should be added to the test suite as well.
+  NSArray<FIRComponent *> *components = [FIRAuth componentsToRegister];
+  XCTAssertTrue(components.count == 1);
+
+  FIRComponent *component = [components firstObject];
+  XCTAssert(component.protocol == @protocol(FIRAuthInterop));
+}
+
 #pragma mark - Helpers
 
 /** @fn mockSecureTokenResponseWithError:
diff --git a/Example/Core/Tests/FIRAppTest.m b/Example/Core/Tests/FIRAppTest.m
index 656f046..d88ed66 100644
--- a/Example/Core/Tests/FIRAppTest.m
+++ b/Example/Core/Tests/FIRAppTest.m
@@ -754,6 +754,7 @@ NSString *const kFIRTestAppName2 = @"test-app-name-2";
 
 #pragma mark - Internal Methods
 
+// TODO: Remove this test once the `getUIDImplementation` block doesn't need to be set in Core.
 - (void)testAuthGetUID {
   [FIRApp configure];
 
diff --git a/Example/Podfile b/Example/Podfile
index dc3acd0..373471f 100644
--- a/Example/Podfile
+++ b/Example/Podfile
@@ -4,6 +4,7 @@
 
 use_frameworks!
 
+pod 'FirebaseAuthInterop', :path => '../'
 pod 'FirebaseCore', :path => '../'
 pod 'GoogleUtilities', :path => '../'