allow installing extra JS binding via the bridge

Reviewed By: mdvacca

Differential Revision: D6957397

fbshipit-source-id: 172905861fbb1c9ed45149e33b406c28ad616cd7

React/CxxBridge/RCTCxxBridge.mm

@@ -515,6 +515,8 @@ struct RCTInstanceCallback : public InstanceCallback {
         std::make_unique<JSBigStdString>("true"));
     }
 #endif
+
+    [self installExtraJSBinding];
   }
 
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
@@ -609,6 +611,16 @@ struct RCTInstanceCallback : public InstanceCallback {
   RCT_PROFILE_END_EVENT(RCTProfileTagAlways, @"");
 }
 
+- (void)installExtraJSBinding
+{
+  if ([self.delegate conformsToProtocol:@protocol(RCTCxxBridgeDelegate)]) {
+    id<RCTCxxBridgeDelegate> cxxDelegate = (id<RCTCxxBridgeDelegate>) self.delegate;
+    if ([cxxDelegate respondsToSelector:@selector(installExtraJSBinding:)]) {
+      [cxxDelegate installExtraJSBinding:self.jsContextRef];
+    }
+  }
+}
+
 - (void)_initModules:(NSArray<id<RCTBridgeModule>> *)modules
    withDispatchGroup:(dispatch_group_t)dispatchGroup
     lazilyDiscovered:(BOOL)lazilyDiscovered

React/CxxBridge/RCTCxxBridgeDelegate.h

@@ -10,6 +10,7 @@
 #include <memory>
 
 #import <React/RCTBridgeDelegate.h>
+#import <jschelpers/JavaScriptCore.h>
 
 namespace facebook {
 namespace react {
@@ -32,4 +33,11 @@ class JSExecutorFactory;
  */
 - (std::unique_ptr<facebook::react::JSExecutorFactory>)jsExecutorFactoryForBridge:(RCTBridge *)bridge;
 
+@optional
+
+/**
+ * Experimental: Perform installation of extra JS binding on the given JS context, as appropriate.
+ */
+- (void)installExtraJSBinding:(JSGlobalContextRef)jsContextRef;
+
 @end