[Init] Add executor providers to RCTBridge's init method

If you construct an RCTBridge you may want to configure the executor. However the constructor synchronously calls `setUp` and sets up the executor. Instead, let the code that constructs the bridge specify the executor and a debug executor up front. This allows for customizing the web view executor with a UIWebView of your choice, or configuring the URL of the debugger proxy that the web socket executor connects to.

Now that RCTRootView takes a bridge in one of its initializers, it is possible to create a bridge with a custom executor and then use that to set up a root view.

Fixes facebook#288

React/Base/RCTBridge.h

@@ -19,13 +19,19 @@
 /**
  * This block can be used to instantiate modules that require additional
  * init parameters, or additional configuration prior to being used.
- * The bridge will call this block to instatiate the modules, and will
+ * The bridge will call this block to instantiate the modules, and will
  * be responsible for invalidating/releasing them when the bridge is destroyed.
  * For this reason, the block should always return new module instances, and
  * module instances should not be shared between bridges.
  */
 typedef NSArray *(^RCTBridgeModuleProviderBlock)(void);
 
+/**
+ * A block that provides a new instance of an RCTJavaScript executor. The bridge
+ * will call this block to define the executor it uses.
+ */
+typedef id<RCTJavaScriptExecutor>(^RCTJavaScriptExecutorProviderBlock)(void);
+
 /**
  * This function returns the module name for a given class.
  */
@@ -46,7 +52,13 @@ extern NSString *RCTBridgeModuleNameForClass(Class bridgeModuleClass);
  */
 - (instancetype)initWithBundlePath:(NSString *)bundlepath
                     moduleProvider:(RCTBridgeModuleProviderBlock)block
-                     launchOptions:(NSDictionary *)launchOptions NS_DESIGNATED_INITIALIZER;
+                     launchOptions:(NSDictionary *)launchOptions
+                     executorBlock:(RCTJavaScriptExecutorProviderBlock)executorBlock
+                debugExecutorBlock:(RCTJavaScriptExecutorProviderBlock)debugExecutorBlock NS_DESIGNATED_INITIALIZER;
+
+- (instancetype)initWithBundlePath:(NSString *)bundlepath
+                    moduleProvider:(RCTBridgeModuleProviderBlock)block
+                     launchOptions:(NSDictionary *)launchOptions;
 
 /**
  * This method is used to call functions in the JavaScript application context.

React/Base/RCTBridge.m

@@ -211,8 +211,6 @@ @implementation RCTModuleMethod
   NSString *_methodName;
 }
 
-static Class _globalExecutorClass;
-
 NS_INLINE NSString *RCTStringUpToFirstArgument(NSString *methodName) {
   NSRange colonRange = [methodName rangeOfString:@":"];
   if (colonRange.length) {
@@ -663,7 +661,9 @@ @implementation RCTBridge
   RCTSparseArray *_modulesByID;
   NSDictionary *_modulesByName;
   id<RCTJavaScriptExecutor> _javaScriptExecutor;
-  Class _executorClass;
+  RCTJavaScriptExecutorProviderBlock _executorBlock;
+  RCTJavaScriptExecutorProviderBlock _debugExecutorBlock;
+  BOOL _usingDebugExecutor;
   NSString *_bundlePath;
   NSDictionary *_launchOptions;
   RCTBridgeModuleProviderBlock _moduleProvider;
@@ -675,21 +675,53 @@ @implementation RCTBridge
 - (instancetype)initWithBundlePath:(NSString *)bundlePath
                     moduleProvider:(RCTBridgeModuleProviderBlock)block
                      launchOptions:(NSDictionary *)launchOptions
+                     executorBlock:(RCTJavaScriptExecutorProviderBlock)executorBlock
+                debugExecutorBlock:(RCTJavaScriptExecutorProviderBlock)debugExecutorBlock
 {
   if ((self = [super init])) {
     _bundlePath = bundlePath;
     _moduleProvider = block;
     _launchOptions = launchOptions;
+    _executorBlock = executorBlock;
+    _debugExecutorBlock = debugExecutorBlock;
     [self setUp];
     [self bindKeys];
   }
 
   return self;
 }
+
+- (instancetype)initWithBundlePath:(NSString *)bundlePath
+                    moduleProvider:(RCTBridgeModuleProviderBlock)block
+                     launchOptions:(NSDictionary *)launchOptions
+{
+  return [self initWithBundlePath:bundlePath
+                   moduleProvider:block
+                    launchOptions:launchOptions
+                    executorBlock:^{ return [[RCTContextExecutor alloc] init]; }
+               debugExecutorBlock:^{
+                 Class executorClass = NSClassFromString(@"RCTWebSocketExecutor");
+                 if (!executorClass) {
+                   RCTLogError(@"WebSocket debugger is not available. Did you forget to include RCTWebSocketExecutor?");
+                   executorClass = [RCTContextExecutor class];
+                 }
+                 return [[executorClass alloc] init];
+               }];
+}
+
 - (void)setUp
 {
-  Class executorClass = _executorClass ?: _globalExecutorClass ?: [RCTContextExecutor class];
-  _javaScriptExecutor = [[executorClass alloc] init];
+  if (_usingDebugExecutor) {
+    if (_debugExecutorBlock) {
+      _javaScriptExecutor = _debugExecutorBlock();
+    } else {
+      RCTLogError(@"Attempting to debug without providing a debug executor; falling back to the default executor");
+      _javaScriptExecutor = _executorBlock();
+    }
+  } else {
+    _javaScriptExecutor = _executorBlock();
+  }
+
   _latestJSExecutor = _javaScriptExecutor;
   _eventDispatcher = [[RCTEventDispatcher alloc] initWithBridge:self];
   _shadowQueue = dispatch_queue_create("com.facebook.ReactKit.ShadowQueue", DISPATCH_QUEUE_SERIAL);
@@ -801,7 +833,7 @@ - (void)bindKeys
                                                           if (!strongSelf) {
                                                             return;
                                                           }
-                                                          strongSelf->_executorClass = Nil;
+                                                          strongSelf->_usingDebugExecutor = NO;
                                                           [strongSelf reload];
                                                         }];
   [[RCTKeyCommands sharedInstance] registerKeyCommandWithInput:@"d"
@@ -811,10 +843,7 @@ - (void)bindKeys
                                                           if (!strongSelf) {
                                                             return;
                                                           }
-                                                          strongSelf->_executorClass = NSClassFromString(@"RCTWebSocketExecutor");
-                                                          if (!strongSelf->_executorClass) {
-                                                            RCTLogError(@"WebSocket debugger is not available. Did you forget to include RCTWebSocketExecutor?");
-                                                          }
+                                                          strongSelf->_usingDebugExecutor = YES;
                                                           [strongSelf reload];
                                                         }];
 #endif