Make delegate method optional (and add type specification to delegate…

… property)

platform/darwin/src/MGLNetworkConfiguration.h

@@ -6,24 +6,23 @@ NS_ASSUME_NONNULL_BEGIN
 
 @class MGLNetworkConfiguration;
 
+@protocol MGLNetworkConfigurationDelegate <NSObject>
+@optional
+
 /**
  :nodoc:
- The `MGLNetworkConfigurationSessionDelegate` protocol provides an `NSURLSession`
- object for the `MGLNetworkConfiguration`. This API should be considered
- experimental, likely to be removed or changed in future releases.
+ Provides an `NSURLSession` object for the specified `MGLNetworkConfiguration`.
+ This API should be considered experimental, likely to be removed or changed in
+ future releases.
 
  This method is called from background threads, i.e. it is not called on the main
  thread.
 
  @note Background sessions (i.e. created with
  `-[NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:]`)
+ and sessions created with a delegate that conforms to `NSURLSessionDataDelegate`
  are not supported at this time.
-
- @note: Sessions created with a delegate that conforms to `NSURLSessionDataDelegate`
- are not supported at this time.
-
  */
-@protocol MGLNetworkConfigurationSessionDelegate <NSObject>
 - (NSURLSession *)sessionForNetworkConfiguration:(MGLNetworkConfiguration *)configuration;
 @end
 
@@ -39,7 +38,7 @@ MGL_EXPORT
  :nodoc:
  Delegate for the `MGLNetworkConfiguration` class.
  */
-@property (nonatomic, weak) id delegate;
+@property (nonatomic, weak) id<MGLNetworkConfigurationDelegate> delegate;
 
 /**
  Returns the shared instance of the `MGLNetworkConfiguration` class.
@@ -56,7 +55,7 @@ MGL_EXPORT
  Assign this object before instantiating any `MGLMapView` object, or using
  `MGLOfflineStorage`
  
- @note: `NSURLSession` objects store a copy of this configuration. Any further changes
+ @note `NSURLSession` objects store a copy of this configuration. Any further changes
  to mutable properties on this configuration object passed to a session’s initializer
  will not affect the behavior of that session.
 

platform/darwin/src/MGLNetworkConfiguration.m

@@ -69,8 +69,8 @@ + (NSURLSessionConfiguration *)defaultSessionConfiguration {
 - (NSURLSession *)sessionForNetworkManager:(MGLNativeNetworkManager *)networkManager {
     // Note: this method is NOT called on the main thread.
     NSURLSession *session;
-    if ([self.delegate conformsToProtocol:@protocol(MGLNetworkConfigurationSessionDelegate)]) {
-        session = [(id<MGLNetworkConfigurationSessionDelegate>)self.delegate sessionForNetworkConfiguration:self];
+    if ([self.delegate respondsToSelector:@selector(sessionForNetworkConfiguration:)]) {
+        session = [self.delegate sessionForNetworkConfiguration:self];
     }
 
     // Check for a background session; string checking is fragile, but this is not
@@ -79,6 +79,11 @@ - (NSURLSession *)sessionForNetworkManager:(MGLNativeNetworkManager *)networkMan
     NSAssert(![session isKindOfClass:NSClassFromString(@"__NSURLBackgroundSession")],
              @"Background NSURLSessions are not yet supported");
 
+    if (session.delegate) {
+        NSAssert(![session.delegate conformsToProtocol:@protocol(NSURLSessionDataDelegate)],
+                 @"Session delegates conforming to NSURLSessionDataDelegate are not yet supported");
+    }
+
     return session;
 }
 

platform/ios/Integration Tests/MGLNetworkConfigurationIntegrationTests.mm

@@ -10,7 +10,7 @@ + (void)testing_clearNativeNetworkManagerDelegate;
 + (id)testing_nativeNetworkManagerDelegate;
 @end
 
-@interface MGLNetworkConfigurationTestDelegate: NSObject <MGLNetworkConfigurationSessionDelegate>
+@interface MGLNetworkConfigurationTestDelegate: NSObject <MGLNetworkConfigurationDelegate>
 @property (nonatomic) NSURLSession *(^handler)();
 @end
 
@@ -284,8 +284,16 @@ - (void)testFailureForNetworkConfigurationWithSessionWithDataDelegate🔒 {
     NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfig
                                                           delegate:delegate
                                                      delegateQueue:nil];
-    [self internalTestNetworkConfigurationWithSession:session shouldDownload:YES];
 
+    BOOL conforms = [session.delegate conformsToProtocol:@protocol(NSURLSessionDataDelegate)];
+    XCTAssert(conforms);
+#ifdef DEBUG
+    if (conforms) {
+        NSLog(@"Session delegates conforming to NSURLSessionDataDelegate are not supported");
+    }
+#else
+    [self internalTestNetworkConfigurationWithSession:session shouldDownload:YES];
+#endif
     [session finishTasksAndInvalidate];
 
     XCTAssertFalse(didCallReceiveData);