[Extensions Bindings] Allow for argument validation without conversion

extensions/renderer/api_binding_hooks.h

 // 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.
 
 #ifndef EXTENSIONS_RENDERER_API_BINDING_HOOKS_H_
 #define EXTENSIONS_RENDERER_API_BINDING_HOOKS_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "extensions/renderer/api_binding_types.h"
+#include "extensions/renderer/argument_spec.h"
 #include "v8/include/v8.h"
 
 namespace gin {
 class Arguments;
 }
 
 namespace extensions {
 class APISignature;
 
 // A class to register custom hooks for given API calls that need different
 // handling. An instance exists for a single API, but can be used across
 // multiple contexts (but only on the same thread).
 // TODO(devlin): We have both C++ and JS custom bindings, but this only allows
 // for registration of C++ handlers. Add JS support.
 class APIBindingHooks {
  public:
+  // The result of checking for hooks to handle a request.
+  enum class RequestResult {
+    HANDLED,             // A custom hook handled the request.
+    INVALID_INVOCATION,  // The request was called with invalid arguments.
+    NOT_HANDLED,         // The request was not handled.
+  };
+
   // The callback to handle an API method. We pass in the expected signature
   // (so the caller can verify arguments, optionally after modifying/"massaging"
   // them) and the passed arguments. The handler is responsible for returning,
   // which depending on the API could mean either returning synchronously
   // through gin::Arguments::Return or asynchronously through a passed callback.
   // TODO(devlin): As we continue expanding the hooks interface, we should allow
   // handlers to register a request so that they don't have to maintain a
   // reference to the callback themselves.
   using HandleRequestHook =
-      base::Callback<void(const APISignature*, gin::Arguments*)>;
+      base::Callback<RequestResult(const APISignature*,
+                                   gin::Arguments*,
+                                   const ArgumentSpec::RefMap&)>;
 
   explicit APIBindingHooks(const binding::RunJSFunction& run_js);
   ~APIBindingHooks();
 
   // Register a custom binding to handle requests.
   void RegisterHandleRequest(const std::string& method_name,
                              const HandleRequestHook& hook);
 
   // Registers a JS script to be compiled and run in order to initialize any JS
   // hooks within a v8 context.
   void RegisterJsSource(v8::Global<v8::String> source,
                         v8::Global<v8::String> resource_name);
 
   // Initializes JS hooks within a context.
   void InitializeInContext(v8::Local<v8::Context> context,
                            const std::string& api_name);
 
   // Looks for a custom hook to handle the given request and, if one exists,
-  // runs it. Returns true if a hook was found and run.
-  bool HandleRequest(const std::string& api_name,
-                     const std::string& method_name,
-                     v8::Local<v8::Context> context,
-                     const APISignature* signature,
-                     gin::Arguments* arguments);
+  // runs it. Returns the result of trying to run the hook, or NOT_HANDLED if no
+  // hook was found.
+  RequestResult HandleRequest(const std::string& api_name,
+                              const std::string& method_name,
+                              v8::Local<v8::Context> context,
+                              const APISignature* signature,
+                              gin::Arguments* arguments,
+                              const ArgumentSpec::RefMap& type_refs);
 
   // Returns a JS interface that can be used to register hooks.
   v8::Local<v8::Object> GetJSHookInterface(const std::string& api_name,
                                            v8::Local<v8::Context> context);
 
  private:
   // Whether we've tried to use any hooks associated with this object.
   bool hooks_used_ = false;
 
   // All registered request handlers.
   std::map<std::string, HandleRequestHook> request_hooks_;
 
   // The script to run to initialize JS hooks, if any.
   v8::Global<v8::String> js_hooks_source_;
 
   // The name of the JS resource for the hooks. Used to create a ScriptOrigin
   // to make exception stack traces more readable.
   v8::Global<v8::String> js_resource_name_;
 
   binding::RunJSFunction run_js_;
 
   DISALLOW_COPY_AND_ASSIGN(APIBindingHooks);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_API_BINDING_HOOKS_H_