Allow multiple configure calls in an extension. (#4436)

* Allow multiple `configure` calls in an extension.

Some extensions have an entry point that gets called multiple times.
Instead of having to check if a default app has already been configured,
allow multiple `configure` calls if and only if it's in an extension and
the FIROptions contents are identical.

* Review comments.

* Updated comment.

Author: ryanwilson

Example/Core/Tests/FIRAppTest.m

@@ -20,6 +20,8 @@
 #import <FirebaseCore/FIRCoreDiagnosticsConnector.h>
 #import <FirebaseCore/FIROptionsInternal.h>
 
+#import <GoogleUtilities/GULAppEnvironmentUtil.h>
+
 NSString *const kFIRTestAppName1 = @"test_app_name_1";
 NSString *const kFIRTestAppName2 = @"test-app-name-2";
 
@@ -214,6 +216,81 @@ - (void)testConfigureWithMultipleApps {
   XCTAssertEqualObjects(app.options.APIKey, kCustomizedAPIKey);
 }
 
+- (void)testConfigureThrowsAfterConfigured {
+  FIROptions *options = [[FIROptions alloc] initWithGoogleAppID:kGoogleAppID
+                                                    GCMSenderID:kGCMSenderID];
+  [FIRApp configureWithOptions:options];
+  XCTAssertNotNil([FIRApp defaultApp]);
+
+  // A second configure call should throw, since Firebase is already configured.
+  XCTAssertThrows([FIRApp configureWithOptions:options]);
+
+  // Test the same with a custom named app.
+  [FIRApp configureWithName:kFIRTestAppName1 options:options];
+  XCTAssertNotNil([FIRApp appNamed:kFIRTestAppName1]);
+
+  // A second configure call should throw, since Firebase is already configured.
+  XCTAssertThrows([FIRApp configureWithName:kFIRTestAppName1 options:options]);
+}
+
+- (void)testConfigureDefaultAppInExtension {
+  id environmentMock = OCMClassMock([GULAppEnvironmentUtil class]);
+  OCMStub([environmentMock isAppExtension]).andReturn(YES);
+
+  // Set up the default app like a standard app.
+  FIROptions *options = [[FIROptions alloc] initWithGoogleAppID:kGoogleAppID
+                                                    GCMSenderID:kGCMSenderID];
+  [FIRApp configureWithOptions:options];
+  XCTAssertNotNil([FIRApp defaultApp]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Configuring with the same set of options shouldn't throw.
+  XCTAssertNoThrow([FIRApp configureWithOptions:options]);
+
+  // Only 1 app should have been configured still, the default app.
+  XCTAssertNotNil([FIRApp defaultApp]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Use a set of a different options to call configure again, which should throw.
+  FIROptions *differentOptions = [[FIROptions alloc] initWithGoogleAppID:@"1:789:ios:789XYZ"
+                                                             GCMSenderID:kGCMSenderID];
+  XCTAssertThrows([FIRApp configureWithOptions:differentOptions]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Explicily stop the environmentMock.
+  [environmentMock stopMocking];
+  environmentMock = nil;
+}
+
+- (void)testConfigureCustomAppInExtension {
+  id environmentMock = OCMClassMock([GULAppEnvironmentUtil class]);
+  OCMStub([environmentMock isAppExtension]).andReturn(YES);
+
+  // Set up a custom named app like a standard app.
+  FIROptions *options = [[FIROptions alloc] initWithGoogleAppID:kGoogleAppID
+                                                    GCMSenderID:kGCMSenderID];
+  [FIRApp configureWithName:kFIRTestAppName1 options:options];
+  XCTAssertNotNil([FIRApp appNamed:kFIRTestAppName1]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Configuring with the same set of options shouldn't throw.
+  XCTAssertNoThrow([FIRApp configureWithName:kFIRTestAppName1 options:options]);
+
+  // Only 1 app should have been configured still.
+  XCTAssertNotNil([FIRApp appNamed:kFIRTestAppName1]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Use a set of a different options to call configure again, which should throw.
+  FIROptions *differentOptions = [[FIROptions alloc] initWithGoogleAppID:@"1:789:ios:789XYZ"
+                                                             GCMSenderID:kGCMSenderID];
+  XCTAssertThrows([FIRApp configureWithName:kFIRTestAppName1 options:differentOptions]);
+  XCTAssertEqual([FIRApp allApps].count, 1);
+
+  // Explicily stop the environmentMock.
+  [environmentMock stopMocking];
+  environmentMock = nil;
+}
+
 - (void)testValidName {
   XCTAssertNoThrow([FIRApp configureWithName:@"aA1_" options:[FIROptions defaultOptions]]);
   XCTAssertNoThrow([FIRApp configureWithName:@"aA1-" options:[FIROptions defaultOptions]]);

Firebase/Core/FIRApp.m

@@ -35,6 +35,8 @@
 #import "Private/FIROptionsInternal.h"
 #import "Private/FIRVersion.h"
 
+#import <GoogleUtilities/GULAppEnvironmentUtil.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;
@@ -160,8 +162,9 @@ + (void)configureWithName:(NSString *)name options:(FIROptions *)options {
 
   if ([name isEqualToString:kFIRDefaultAppName]) {
     if (sDefaultApp) {
-      [NSException raise:kFirebaseCoreErrorDomain
-                  format:@"Default app has already been configured."];
+      // The default app already exixts. Handle duplicate `configure` calls and return.
+      [self appWasConfiguredTwice:sDefaultApp usingOptions:options];
+      return;
     }
 
     FIRLogDebug(kFIRLoggerCore, @"I-COR000001", @"Configuring the default app.");
@@ -177,8 +180,9 @@ + (void)configureWithName:(NSString *)name options:(FIROptions *)options {
 
     @synchronized(self) {
       if (sAllApps && sAllApps[name]) {
-        [NSException raise:kFirebaseCoreErrorDomain
-                    format:@"App named %@ has already been configured.", name];
+        // The app already exists. Handle a duplicate `configure` call and return.
+        [self appWasConfiguredTwice:sAllApps[name] usingOptions:options];
+        return;
       }
     }
 
@@ -200,6 +204,36 @@ + (void)configureWithName:(NSString *)name options:(FIROptions *)options {
   }
 }
 
+/// Called when `configure` has been called multiple times for the same app. This can either throw
+/// an exception (most cases) or ignore the duplicate configuration in situations where it's allowed
+/// like an extension.
++ (void)appWasConfiguredTwice:(FIRApp *)app usingOptions:(FIROptions *)options {
+  // Only extensions should potentially be able to call `configure` more than once.
+  if (![GULAppEnvironmentUtil isAppExtension]) {
+    // Throw an exception since this is now an invalid state.
+    if (app.isDefaultApp) {
+      [NSException raise:kFirebaseCoreErrorDomain
+                  format:@"Default app has already been configured."];
+    } else {
+      [NSException raise:kFirebaseCoreErrorDomain
+                  format:@"App named %@ has already been configured.", app.name];
+    }
+  }
+
+  // In an extension, the entry point could be called multiple times. As long as the options are
+  // identical we should allow multiple `configure` calls.
+  if ([options isEqual:app.options]) {
+    // Everything is identical but the extension's lifecycle triggered `configure` twice.
+    // Ignore duplicate calls and return since everything should still be in a valid state.
+    FIRLogDebug(kFIRLoggerCore, @"I-COR000035",
+                @"Ignoring second `configure` call in an extension.");
+    return;
+  } else {
+    [NSException raise:kFirebaseCoreErrorDomain
+                format:@"App named %@ has already been configured.", app.name];
+  }
+}
+
 + (FIRApp *)defaultApp {
   if (sDefaultApp) {
     return sDefaultApp;

Firebase/Core/FIROptions.m

@@ -330,6 +330,59 @@ - (void)setAppGroupID:(NSString *)appGroupID {
   _appGroupID = [appGroupID copy];
 }
 
+#pragma mark - Equality
+
+- (BOOL)isEqual:(id)object {
+  if (!object || ![object isKindOfClass:[FIROptions class]]) {
+    return NO;
+  }
+
+  return [self isEqualToOptions:(FIROptions *)object];
+}
+
+- (BOOL)isEqualToOptions:(FIROptions *)options {
+  // Skip any non-FIROptions classes.
+  if (![options isKindOfClass:[FIROptions class]]) {
+    return NO;
+  }
+
+  // Check the internal dictionary and custom properties for differences.
+  if (![options.optionsDictionary isEqualToDictionary:self.optionsDictionary]) {
+    return NO;
+  }
+
+  // Validate extra properties not contained in the dictionary. Only validate it if one of the
+  // objects has the property set.
+  if ((options.deepLinkURLScheme != nil || self.deepLinkURLScheme != nil) &&
+      ![options.deepLinkURLScheme isEqualToString:self.deepLinkURLScheme]) {
+    return NO;
+  }
+
+  if ((options.appGroupID != nil || self.appGroupID != nil) &&
+      ![options.appGroupID isEqualToString:self.appGroupID]) {
+    return NO;
+  }
+
+  // Validate the Analytics options haven't changed with the Info.plist.
+  if (![options.analyticsOptionsDictionary isEqualToDictionary:self.analyticsOptionsDictionary]) {
+    return NO;
+  }
+
+  // We don't care about the `editingLocked` or `usingOptionsFromDefaultPlist` properties since
+  // those relate to lifecycle and construction, we only care if the contents of the options
+  // themselves are equal.
+  return YES;
+}
+
+- (NSUInteger)hash {
+  // This is strongly recommended for any object that implements a custom `isEqual:` method to
+  // ensure that dictionary and set behavior matches other `isEqual:` checks.
+  // Note: `self.analyticsOptionsDictionary` was left out here since it solely relies on the
+  // contents of the main bundle's `Info.plist`. We should avoid reading that file and the contents
+  // should be identical.
+  return self.optionsDictionary.hash ^ self.deepLinkURLScheme.hash ^ self.appGroupID.hash;
+}
+
 #pragma mark - Internal instance methods
 
 - (NSDictionary *)analyticsOptionsDictionaryWithInfoDictionary:(NSDictionary *)infoDictionary {