[Extensions Bindings] Allow custom hooks to return values, throw

extensions/renderer/api_binding.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/renderer/api_binding.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 192 matching lines @@
   // catching it.
   if (invalid_invocation) {
     arguments->ThrowTypeError("Invalid invocation");
     return;
   }
 
   {
     v8::TryCatch try_catch(isolate);
     APIBindingHooks::RequestResult hooks_result =
         APIBindingHooks::RequestResult::NOT_HANDLED;
+    v8::Local<v8::Value> return_value;
     hooks_result = binding_hooks_->HandleRequest(api_name_, name, context,
                                                  signature, &argument_list,
-                                                 *type_refs_);
+                                                 *type_refs_, &return_value);
 
     switch (hooks_result) {
       case APIBindingHooks::RequestResult::INVALID_INVOCATION:
         invalid_invocation = true;
         // Throw a type error below so that it's not caught by our try-catch.
         break;
       case APIBindingHooks::RequestResult::THROWN:
         DCHECK(try_catch.HasCaught());
         try_catch.ReThrow();
         return;
       case APIBindingHooks::RequestResult::HANDLED:
+        if (!return_value.IsEmpty())

[jbroman, 2017/01/02 20:05:46]

Do we expect this to ever be IsEmpty is a case that shouldn't be a DCHECK
failure (i.e. a programming failure)?

Every JS function returns a value, even if it's |undefined|.

[Devlin, 2017/01/04 18:38:07]

In the case of a native (c++) handler hook without a return value, I'd expect
this to happen.

+          arguments->Return(return_value);
         return;  // Our work here is done.
       case APIBindingHooks::RequestResult::NOT_HANDLED:
         break;  // Handle in the default manner.
     }
   }
 
   if (invalid_invocation) {
     arguments->ThrowTypeError("Invalid invocation");
     return;
   }
@@ skipping 15 matching lines @@
     arguments->ThrowTypeError("Invalid invocation");
     return;
   }
 
   DCHECK(converted_arguments);
   method_callback_.Run(name, std::move(converted_arguments), isolate, context,
                        callback);
 }
 
 }  // namespace extensions