Add context executor API for sync hooks

Summary:
public

This exposes a proper API for adding synchronous callbacks to JS, as an optional feature of the executor.

This is based on nicklockwood's work in D2764492, but avoids refactoring bridge/executor interactions for the time being, since we agree on this API and can move the actual callsites around later.

Reviewed By: nicklockwood

Differential Revision: D2799506

fb-gh-sync-id: af209d9a0be927f3404205feb16e59745cc37aec

Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m

@@ -187,7 +187,7 @@ RCT_EXPORT_METHOD(test:(__unused NSString *)a
                                               moduleProvider:nil
                                                launchOptions:nil];
     id executor = [bridge.batchedBridge valueForKey:@"javaScriptExecutor"];
-    RUN_RUNLOOP_WHILE(!(weakContext = [executor valueForKey:@"context"]));
+    RUN_RUNLOOP_WHILE(!(weakContext = [executor valueForKey:@"_context"]));
     XCTAssertNotNil(weakContext, @"RCTJavaScriptContext should have been created");
     (void)bridge;
   }

Libraries/RCTTest/RCTTestRunner.m

@@ -136,7 +136,7 @@ expectErrorBlock:(BOOL(^)(NSString *error))expectErrorBlock
     // (we can only do this now, since it's been lazily initialized)
     id jsExecutor = [bridge valueForKeyPath:@"batchedBridge.javaScriptExecutor"];
     if ([jsExecutor isKindOfClass:[RCTJSCExecutor class]]) {
-      weakJSContext = [jsExecutor valueForKey:@"context"];
+      weakJSContext = [jsExecutor valueForKey:@"_context"];
     }
     [rootView removeFromSuperview];
 

React/Base/RCTJavaScriptExecutor.h

@@ -85,4 +85,10 @@ typedef void (^RCTJavaScriptCallback)(id json, NSError *error);
  */
 - (void)executeAsyncBlockOnJavaScriptQueue:(dispatch_block_t)block;
 
+/**
+ * For executors that support it, this method can be used to add a synchronous
+ * callback function for communicating with the javascript context.
+ */
+- (void)addSynchronousHookWithName:(NSString *)name usingBlock:(id)block;
+
 @end

React/Executors/RCTJSCExecutor.m

@@ -215,99 +215,113 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
   return [self initWithJavaScriptThread:javaScriptThread context:context];
 }
 
-- (void)setUp
+- (RCTJavaScriptContext *)context
+{
+  RCTAssertThread(_javaScriptThread, @"Must be called on JS thread.");
+
+  if (!self.isValid) {
+    return nil;
+  }
+
+  if (!_context) {
+    JSContext *context = [JSContext new];
+    _context = [[RCTJavaScriptContext alloc] initWithJSContext:context];
+  }
+
+  return _context;
+}
+
+- (void)addSynchronousHookWithName:(NSString *)name usingBlock:(id)block
 {
   __weak RCTJSCExecutor *weakSelf = self;
   [self executeBlockOnJavaScriptQueue:^{
-    RCTJSCExecutor *strongSelf = weakSelf;
+    weakSelf.context.context[name] = block;
-    if (!strongSelf.isValid) {
+  }];
-      return;
 }
 
-    if (!strongSelf->_context) {
+- (void)setUp
-      JSContext *context = [JSContext new];
+{
-      strongSelf->_context = [[RCTJavaScriptContext alloc] initWithJSContext:context];
+  __weak RCTJSCExecutor *weakSelf = self;
-    }
+  [self addSynchronousHookWithName:@"noop" usingBlock:^{}];
 
-    __weak RCTBridge *weakBridge = strongSelf->_bridge;
+  [self addSynchronousHookWithName:@"nativeLoggingHook" usingBlock:^(NSString *message, NSNumber *logLevel) {
-    JSContext *context = strongSelf->_context.context;
-
-    context[@"noop"] = ^{};
-
-    context[@"nativeLoggingHook"] = ^(NSString *message, NSNumber *logLevel) {
     RCTLogLevel level = RCTLogLevelInfo;
     if (logLevel) {
       level = MAX(level, logLevel.integerValue);
     }
 
     _RCTLogJavaScriptInternal(level, message);
-    };
+  }];
 
-    context[@"nativeRequireModuleConfig"] = ^NSString *(NSString *moduleName) {
+  [self addSynchronousHookWithName:@"nativeRequireModuleConfig" usingBlock:^NSString *(NSString *moduleName) {
-      if (!weakSelf.valid) {
+    RCTJSCExecutor *strongSelf = weakSelf;
+    if (!strongSelf.valid) {
       return nil;
     }
-      NSArray *config = [weakBridge configForModuleName:moduleName];
+
+    NSArray *config = [strongSelf->_bridge configForModuleName:moduleName];
     if (config) {
       return RCTJSONStringify(config, NULL);
     }
-      return nil;
-    };
 
-    context[@"nativeFlushQueueImmediate"] = ^(NSArray<NSArray *> *calls){
+    return nil;
-      if (!weakSelf.valid || !calls) {
+  }];
+
+  [self addSynchronousHookWithName:@"nativeFlushQueueImmediate" usingBlock:^(NSArray<NSArray *> *calls){
+    RCTJSCExecutor *strongSelf = weakSelf;
+    if (!strongSelf.valid || !calls) {
       return;
     }
-      [weakBridge handleBuffer:calls batchEnded:NO];
-    };
 
-    context[@"nativePerformanceNow"] = ^{
+    [strongSelf->_bridge handleBuffer:calls batchEnded:NO];
+  }];
+
+  [self addSynchronousHookWithName:@"nativePerformanceNow" usingBlock:^{
     return @(CACurrentMediaTime() * 1000);
-    };
+  }];
 
 #if RCT_DEV
-
   if (RCTProfileIsProfiling()) {
-      context[@"__RCTProfileIsProfiling"] = @YES;
+    // Cheating, since it's not a "hook", but meh
+    [self addSynchronousHookWithName:@"__RCTProfileIsProfiling" usingBlock:@YES];
   }
 
   CFMutableDictionaryRef cookieMap = CFDictionaryCreateMutable(NULL, 0, NULL, NULL);
-    context[@"nativeTraceBeginAsyncSection"] = ^(uint64_t tag, NSString *name, NSUInteger cookie) {
+  [self addSynchronousHookWithName:@"nativeTraceBeginAsyncSection" usingBlock:^(uint64_t tag, NSString *name, NSUInteger cookie) {
     NSUInteger newCookie = RCTProfileBeginAsyncEvent(tag, name, nil);
     CFDictionarySetValue(cookieMap, (const void *)cookie, (const void *)newCookie);
-    };
+  }];
 
-    context[@"nativeTraceEndAsyncSection"] = ^(uint64_t tag, NSString *name, NSUInteger cookie) {
+  [self addSynchronousHookWithName:@"nativeTraceEndAsyncSection" usingBlock:^(uint64_t tag, NSString *name, NSUInteger cookie) {
     NSUInteger newCookie = (NSUInteger)CFDictionaryGetValue(cookieMap, (const void *)cookie);
     RCTProfileEndAsyncEvent(tag, @"js,async", newCookie, name, nil);
     CFDictionaryRemoveValue(cookieMap, (const void *)cookie);
-    };
+  }];
 
-    context[@"nativeTraceBeginSection"] = ^(NSNumber *tag, NSString *profileName){
+  [self addSynchronousHookWithName:@"nativeTraceBeginSection" usingBlock:^(NSNumber *tag, NSString *profileName){
     static int profileCounter = 1;
     if (!profileName) {
       profileName = [NSString stringWithFormat:@"Profile %d", profileCounter++];
     }
 
     RCT_PROFILE_BEGIN_EVENT(tag.longLongValue, profileName, nil);
-    };
+  }];
 
-    context[@"nativeTraceEndSection"] = ^(NSNumber *tag) {
+  [self addSynchronousHookWithName:@"nativeTraceEndSection" usingBlock:^(NSNumber *tag) {
     RCT_PROFILE_END_EVENT(tag.longLongValue, @"console", nil);
-    };
+  }];
 
-    RCTInstallJSCProfiler(_bridge, strongSelf->_context.ctx);
+  [self executeBlockOnJavaScriptQueue:^{
+    RCTInstallJSCProfiler(_bridge, self.context.ctx);
+  }];
 
   for (NSString *event in @[RCTProfileDidStartProfiling, RCTProfileDidEndProfiling]) {
-      [[NSNotificationCenter defaultCenter] addObserver:strongSelf
+    [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(toggleProfilingFlag:)
                                                  name:event
                                                object:nil];
   }
-
 #endif
-
-  }];
 }
 
 - (void)toggleProfilingFlag:(NSNotification *)notification