Start to use the Obj-C JSContext instead of the C API

Summary: The Obj-C API is usually easier to work with, and also makes it very easy to use the C API when necessary (performance, for example). This diff just switches the designated initializer of RCTContextExecutor to take a JSContext instead of JSGlobalContextRef, but the old initializer still works if needed.

I was doing some memory leak investigation and it is easier with ARC so I wanted to incrementally move the executor to Obj-C.
Closes https://github.com/facebook/react-native/pull/2159

Reviewed By: svcscm

Differential Revision: D2554890

Pulled By: tadeuzagallo

fb-gh-sync-id: 75b96d04cddff68fa3daf5d0fafdffad21dae307

React/Executors/RCTContextExecutor.h

@@ -19,10 +19,16 @@
 @interface RCTContextExecutor : NSObject <RCTJavaScriptExecutor>
 
 /**
- * Configures the executor to run JavaScript on a custom performer.
+ * Configures the executor to run JavaScript on a specific thread with a given JS context.
  * You probably don't want to use this; use -init instead.
  */
 - (instancetype)initWithJavaScriptThread:(NSThread *)javaScriptThread
-                        globalContextRef:(JSGlobalContextRef)context NS_DESIGNATED_INITIALIZER;
+                                 context:(JSContext *)context NS_DESIGNATED_INITIALIZER;
+
+/**
+ * Like -[initWithJavaScriptThread:context:] but uses JSGlobalContextRef from JavaScriptCore's C API.
+ */
+- (instancetype)initWithJavaScriptThread:(NSThread *)javaScriptThread
+                        globalContextRef:(JSGlobalContextRef)contextRef;
 
 @end

React/Executors/RCTContextExecutor.m

@@ -42,9 +42,10 @@ static NSString * const RCTJSCProfilerEnabledDefaultsKey = @"RCTJSCProfilerEnabl
 
 @interface RCTJavaScriptContext : NSObject <RCTInvalidating>
 
+@property (nonatomic, strong, readonly) JSContext *context;
 @property (nonatomic, assign, readonly) JSGlobalContextRef ctx;
 
-- (instancetype)initWithJSContext:(JSGlobalContextRef)context NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithJSContext:(JSContext *)context NS_DESIGNATED_INITIALIZER;
 
 @end
 
@@ -53,10 +54,10 @@ static NSString * const RCTJSCProfilerEnabledDefaultsKey = @"RCTJSCProfilerEnabl
   RCTJavaScriptContext *_self;
 }
 
-- (instancetype)initWithJSContext:(JSGlobalContextRef)context
+- (instancetype)initWithJSContext:(JSContext *)context
 {
   if ((self = [super init])) {
-    _ctx = context;
+    _context = context;
     _self = self;
   }
   return self;
@@ -64,16 +65,20 @@ static NSString * const RCTJSCProfilerEnabledDefaultsKey = @"RCTJSCProfilerEnabl
 
 RCT_NOT_IMPLEMENTED(-(instancetype)init)
 
+- (JSGlobalContextRef)ctx
+{
+  return _context.JSGlobalContextRef;
+}
+
 - (BOOL)isValid
 {
-  return _ctx != NULL;
+  return _context != nil;
 }
 
 - (void)invalidate
 {
   if (self.isValid) {
-    JSGlobalContextRelease(_ctx);
-    _ctx = NULL;
+    _context = nil;
     _self = nil;
   }
 }
@@ -282,11 +287,11 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
   javaScriptThread.threadPriority = [NSThread mainThread].threadPriority;
   [javaScriptThread start];
 
-  return [self initWithJavaScriptThread:javaScriptThread globalContextRef:NULL];
+  return [self initWithJavaScriptThread:javaScriptThread context:nil];
 }
 
 - (instancetype)initWithJavaScriptThread:(NSThread *)javaScriptThread
-                        globalContextRef:(JSGlobalContextRef)context
+                                 context:(JSContext *)context
 {
   RCTAssert(javaScriptThread != nil,
             @"Can't initialize RCTContextExecutor without a javaScriptThread");
@@ -301,10 +306,8 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
         return;
       }
       // Assumes that no other JS tasks are scheduled before.
-      JSGlobalContextRef ctx;
       if (context) {
-        ctx = JSGlobalContextRetain(context);
-        strongSelf->_context = [[RCTJavaScriptContext alloc] initWithJSContext:ctx];
+        strongSelf->_context = [[RCTJavaScriptContext alloc] initWithJSContext:context];
       }
     }];
   }
@@ -312,6 +315,13 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
   return self;
 }
 
+- (instancetype)initWithJavaScriptThread:(NSThread *)javaScriptThread
+                        globalContextRef:(JSGlobalContextRef)contextRef
+{
+  JSContext *context = contextRef ? [JSContext contextWithJSGlobalContextRef:contextRef] : nil;
+  return [self initWithJavaScriptThread:javaScriptThread context:context];
+}
+
 - (void)setUp
 {
   __weak RCTContextExecutor *weakSelf = self;
@@ -321,8 +331,8 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
       return;
     }
     if (!strongSelf->_context) {
-      JSGlobalContextRef ctx = JSGlobalContextCreate(NULL);
-      strongSelf->_context = [[RCTJavaScriptContext alloc] initWithJSContext:ctx];
+      JSContext *context = [[JSContext alloc] init];
+      strongSelf->_context = [[RCTJavaScriptContext alloc] initWithJSContext:context];
     }
     [strongSelf _addNativeHook:RCTNativeLoggingHook withName:"nativeLoggingHook"];
     [strongSelf _addNativeHook:RCTNoop withName:"noop"];