chrome/renderer/extensions/module_system.cc

// Copyright (c) 2012 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 "chrome/renderer/extensions/module_system.h"

#include "base/bind.h"
#include "base/stl_util.h"
#include "base/string_util.h"
#include "base/stringprintf.h"
#include "chrome/common/extensions/extension_messages.h"
#include "chrome/renderer/extensions/chrome_v8_context.h"
#include "chrome/renderer/extensions/console.h"
#include "content/public/renderer/render_view.h"
#include "third_party/WebKit/Source/WebKit/chromium/public/WebScopedMicrotaskSuppression.h"

namespace extensions {

namespace {

const char* kModuleSystem = "module_system";
const char* kModuleName = "module_name";
const char* kModuleField = "module_field";
const char* kModulesField = "modules";

// Formats |try_catch| as a nice string.
std::string CreateExceptionString(const v8::TryCatch& try_catch) {
  v8::Handle<v8::Message> message(try_catch.Message());
  if (message.IsEmpty()) {
    return "try_catch has no message";
  }

  std::string resource_name = "<unknown resource>";
  if (!message->GetScriptResourceName().IsEmpty()) {
    v8::String::Utf8Value resource_name_v8(
        message->GetScriptResourceName()->ToString());
    resource_name.assign(*resource_name_v8, resource_name_v8.length());
  }

  std::string error_message = "<no error message>";
  if (!message->Get().IsEmpty()) {
    v8::String::Utf8Value error_message_v8(message->Get());
    error_message.assign(*error_message_v8, error_message_v8.length());
  }

  return base::StringPrintf("%s:%d: %s",
                            resource_name.c_str(),
                            message->GetLineNumber(),
                            error_message.c_str());
}

// Fatally dumps the debug info from |try_catch| to the console.
// Don't use this for logging exceptions that might originate in external code!
void DumpException(const v8::TryCatch& try_catch) {
  v8::HandleScope handle_scope;

  std::string stack_trace = "<stack trace unavailable>";
  if (!try_catch.StackTrace().IsEmpty()) {
    v8::String::Utf8Value stack_value(try_catch.StackTrace());
    if (*stack_value)
      stack_trace.assign(*stack_value, stack_value.length());
    else
      stack_trace = "<could not convert stack trace to string>";
  }

  console::Fatal(v8::Context::GetCalling(),
                 CreateExceptionString(try_catch) + "{" + stack_trace + "}");
}

} // namespace

ModuleSystem::ModuleSystem(v8::Handle<v8::Context> context,
                           SourceMap* source_map)
    : ObjectBackedNativeHandler(context),
      source_map_(source_map),
      natives_enabled_(0) {
  RouteFunction("require",
      base::Bind(&ModuleSystem::RequireForJs, base::Unretained(this)));
  RouteFunction("requireNative",
      base::Bind(&ModuleSystem::RequireNative, base::Unretained(this)));

  v8::Handle<v8::Object> global(context->Global());
  global->SetHiddenValue(v8::String::New(kModulesField), v8::Object::New());
  global->SetHiddenValue(v8::String::New(kModuleSystem),
                         v8::External::New(this));
}

ModuleSystem::~ModuleSystem() {
  Invalidate();
}

void ModuleSystem::Invalidate() {
  if (!is_valid())
    return;

  // Clear the module system properties from the global context. It's polite,
  // and we use this as a signal in lazy handlers that we no longer exist.
  {
    v8::HandleScope scope;
    v8::Handle<v8::Object> global = v8_context()->Global();
    global->DeleteHiddenValue(v8::String::New(kModulesField));
    global->DeleteHiddenValue(v8::String::New(kModuleSystem));
  }

  // Invalidate all of the successfully required handlers we own.
  for (NativeHandlerMap::iterator it = native_handler_map_.begin();
       it != native_handler_map_.end(); ++it) {
    it->second->Invalidate();
  }

  ObjectBackedNativeHandler::Invalidate();
}

ModuleSystem::NativesEnabledScope::NativesEnabledScope(
    ModuleSystem* module_system)
    : module_system_(module_system) {
  module_system_->natives_enabled_++;
}

ModuleSystem::NativesEnabledScope::~NativesEnabledScope() {
  module_system_->natives_enabled_--;
  CHECK_GE(module_system_->natives_enabled_, 0);
}

void ModuleSystem::HandleException(const v8::TryCatch& try_catch) {
  if (exception_handler_)
    exception_handler_->HandleUncaughtException();
  else
    DumpException(try_catch);
}

v8::Handle<v8::Value> ModuleSystem::Require(const std::string& module_name) {
  v8::HandleScope handle_scope;
  return handle_scope.Close(
      RequireForJsInner(v8::String::New(module_name.c_str())));
}

v8::Handle<v8::Value> ModuleSystem::RequireForJs(const v8::Arguments& args) {
  v8::HandleScope handle_scope;
  v8::Handle<v8::String> module_name = args[0]->ToString();
  return handle_scope.Close(RequireForJsInner(module_name));
}

v8::Handle<v8::Value> ModuleSystem::RequireForJsInner(
    v8::Handle<v8::String> module_name) {
  v8::HandleScope handle_scope;
  v8::Context::Scope context_scope(v8_context());

  v8::Handle<v8::Object> global(v8_context()->Global());

  // The module system might have been deleted. This can happen if a different
  // context keeps a reference to us, but our frame is destroyed (e.g.
  // background page keeps reference to chrome object in a closed popup).
  v8::Handle<v8::Value> modules_value =
      global->GetHiddenValue(v8::String::New(kModulesField));
  if (modules_value.IsEmpty() || modules_value->IsUndefined()) {
    console::Warn(v8::Context::GetCalling(), "Extension view no longer exists");
    return v8::Undefined();
  }

  v8::Handle<v8::Object> modules(v8::Handle<v8::Object>::Cast(modules_value));
  v8::Handle<v8::Value> exports(modules->Get(module_name));
  if (!exports->IsUndefined())
    return handle_scope.Close(exports);

  std::string module_name_str = *v8::String::AsciiValue(module_name);
  v8::Handle<v8::Value> source(GetSource(module_name_str));
  if (source.IsEmpty() || source->IsUndefined()) {
    console::Error(v8::Context::GetCalling(),
                   "No source for require(" + module_name_str + ")");
    return v8::Undefined();
  }
  v8::Handle<v8::String> wrapped_source(WrapSource(
      v8::Handle<v8::String>::Cast(source)));
  // Modules are wrapped in (function(){...}) so they always return functions.
  v8::Handle<v8::Value> func_as_value = RunString(wrapped_source, module_name);
  if (func_as_value.IsEmpty() || func_as_value->IsUndefined()) {
    console::Error(v8::Context::GetCalling(),
                   "Bad source for require(" + module_name_str + ")");
    return v8::Undefined();
  }

  v8::Handle<v8::Function> func = v8::Handle<v8::Function>::Cast(func_as_value);

  exports = v8::Object::New();
  v8::Handle<v8::Object> natives(NewInstance());
  v8::Handle<v8::Value> args[] = {
    natives->Get(v8::String::NewSymbol("require")),
    natives->Get(v8::String::NewSymbol("requireNative")),
    exports,
  };
  {
    WebKit::WebScopedMicrotaskSuppression suppression;
    v8::TryCatch try_catch;
    try_catch.SetCaptureMessage(true);
    func->Call(global, 3, args);
    if (try_catch.HasCaught()) {
      HandleException(try_catch);
      return v8::Undefined();
    }
  }
  modules->Set(module_name, exports);
  return handle_scope.Close(exports);
}

v8::Local<v8::Value> ModuleSystem::CallModuleMethod(
    const std::string& module_name,
    const std::string& method_name) {
  std::vector<v8::Handle<v8::Value> > args;
  return CallModuleMethod(module_name, method_name, &args);
}

v8::Local<v8::Value> ModuleSystem::CallModuleMethod(
    const std::string& module_name,
    const std::string& method_name,
    std::vector<v8::Handle<v8::Value> >* args) {
  v8::HandleScope handle_scope;
  v8::Local<v8::Value> module =
      v8::Local<v8::Value>::New(
          RequireForJsInner(v8::String::New(module_name.c_str())));
  if (module.IsEmpty() || !module->IsObject()) {
    console::Error(
        v8::Context::GetCalling(),
        "Failed to get module " + module_name + " to call " + method_name);
    return handle_scope.Close(v8::Undefined());
  }

  v8::Local<v8::Value> value =
      v8::Handle<v8::Object>::Cast(module)->Get(
          v8::String::New(method_name.c_str()));
  if (value.IsEmpty() || !value->IsFunction()) {
    console::Error(v8::Context::GetCalling(),
                   module_name + "." + method_name + " is not a function");
    return handle_scope.Close(v8::Undefined());
  }

  v8::Handle<v8::Function> func =
      v8::Handle<v8::Function>::Cast(value);
  v8::Handle<v8::Object> global(v8_context()->Global());
  v8::Local<v8::Value> result;
  {
    WebKit::WebScopedMicrotaskSuppression suppression;
    v8::TryCatch try_catch;
    try_catch.SetCaptureMessage(true);
    result = func->Call(global, args->size(), vector_as_array(args));
    if (try_catch.HasCaught())
      HandleException(try_catch);
  }
  return handle_scope.Close(result);
}

void ModuleSystem::RegisterNativeHandler(const std::string& name,
    scoped_ptr<NativeHandler> native_handler) {
  native_handler_map_[name] =
      linked_ptr<NativeHandler>(native_handler.release());
}

void ModuleSystem::OverrideNativeHandlerForTest(const std::string& name) {
  overridden_native_handlers_.insert(name);
}

void ModuleSystem::RunString(const std::string& code, const std::string& name) {
  v8::HandleScope handle_scope;
  RunString(v8::String::New(code.c_str()), v8::String::New(name.c_str()));
}

// static
v8::Handle<v8::Value> ModuleSystem::NativeLazyFieldGetter(
    v8::Local<v8::String> property, const v8::AccessorInfo& info) {
  return LazyFieldGetterInner(property,
                              info,
                              &ModuleSystem::RequireNativeFromString);
}

// static
v8::Handle<v8::Value> ModuleSystem::LazyFieldGetter(
    v8::Local<v8::String> property, const v8::AccessorInfo& info) {
  return LazyFieldGetterInner(property, info, &ModuleSystem::Require);
}

// static
v8::Handle<v8::Value> ModuleSystem::LazyFieldGetterInner(
    v8::Local<v8::String> property,
    const v8::AccessorInfo& info,
    RequireFunction require_function) {
  CHECK(!info.Data().IsEmpty());
  CHECK(info.Data()->IsObject());
  v8::HandleScope handle_scope;
  v8::Handle<v8::Object> parameters = v8::Handle<v8::Object>::Cast(info.Data());
  // This context should be the same as v8_context().
  v8::Handle<v8::Context> context = parameters->CreationContext();
  v8::Handle<v8::Object> global(context->Global());
  v8::Handle<v8::Value> module_system_value =
      global->GetHiddenValue(v8::String::New(kModuleSystem));
  if (module_system_value.IsEmpty() || !module_system_value->IsExternal()) {
    // ModuleSystem has been deleted.
    // TODO(kalman): See comment in header file.
    console::Warn(v8::Context::GetCalling(),
                  "Module system has been deleted, does extension view exist?");
    return v8::Undefined();
  }

  ModuleSystem* module_system = static_cast<ModuleSystem*>(
      v8::Handle<v8::External>::Cast(module_system_value)->Value());

  std::string name = *v8::String::AsciiValue(
      parameters->Get(v8::String::New(kModuleName))->ToString());

  // Switch to our v8 context because we need functions created while running
  // the require()d module to belong to our context, not the current one.
  v8::Context::Scope context_scope(context);
  NativesEnabledScope natives_enabled_scope(module_system);

  v8::TryCatch try_catch;
  v8::Handle<v8::Value> module_value = (module_system->*require_function)(name);
  if (try_catch.HasCaught()) {
    module_system->HandleException(try_catch);
    return v8::Undefined();
  }
  if (module_value.IsEmpty() || !module_value->IsObject()) {
    // require_function will have already logged this, we don't need to.
    return v8::Undefined();
  }

  v8::Handle<v8::Object> module = v8::Handle<v8::Object>::Cast(module_value);
  v8::Handle<v8::String> field =
      parameters->Get(v8::String::New(kModuleField))->ToString();

  if (!module->Has(field)) {
    std::string field_str = *v8::String::AsciiValue(field);
    console::Fatal(v8::Context::GetCalling(),
                   "Lazy require of " + name + "." + field_str + " did not " +
                   "set the " + field_str + " field");
    return v8::Undefined();
  }

  v8::Local<v8::Value> new_field = module->Get(field);
  if (try_catch.HasCaught()) {
    module_system->HandleException(try_catch);
    return v8::Undefined();
  }

  // Ok for it to be undefined, among other things it's how bindings signify
  // that the extension doesn't have permission to use them.
  CHECK(!new_field.IsEmpty());

  // Delete the getter and set this field to |new_field| so the same object is
  // returned every time a certain API is accessed.
  v8::Handle<v8::Object> object = info.This();
  object->Delete(property);
  object->Set(property, new_field);
  return handle_scope.Close(new_field);
}

void ModuleSystem::SetLazyField(v8::Handle<v8::Object> object,
                                const std::string& field,
                                const std::string& module_name,
                                const std::string& module_field) {
  SetLazyField(object, field, module_name, module_field,
      &ModuleSystem::LazyFieldGetter);
}

void ModuleSystem::SetLazyField(v8::Handle<v8::Object> object,
                                const std::string& field,
                                const std::string& module_name,
                                const std::string& module_field,
                                v8::AccessorGetter getter) {
  v8::HandleScope handle_scope;
  v8::Handle<v8::Object> parameters = v8::Object::New();
  parameters->Set(v8::String::New(kModuleName),
                  v8::String::New(module_name.c_str()));
  parameters->Set(v8::String::New(kModuleField),
                  v8::String::New(module_field.c_str()));
  object->SetAccessor(v8::String::New(field.c_str()),
                      getter,
                      NULL,
                      parameters);
}

void ModuleSystem::SetNativeLazyField(v8::Handle<v8::Object> object,
                                      const std::string& field,
                                      const std::string& module_name,
                                      const std::string& module_field) {
  SetLazyField(object, field, module_name, module_field,
      &ModuleSystem::NativeLazyFieldGetter);
}

v8::Handle<v8::Value> ModuleSystem::RunString(v8::Handle<v8::String> code,
                                              v8::Handle<v8::String> name) {
  v8::HandleScope handle_scope;

  WebKit::WebScopedMicrotaskSuppression suppression;
  v8::TryCatch try_catch;
  try_catch.SetCaptureMessage(true);
  v8::Handle<v8::Script> script(v8::Script::New(code, name));
  if (try_catch.HasCaught()) {
    HandleException(try_catch);
    return v8::Undefined();
  }

  v8::Handle<v8::Value> result = script->Run();
  if (try_catch.HasCaught()) {
    HandleException(try_catch);
    return v8::Undefined();
  }

  return handle_scope.Close(result);
}

v8::Handle<v8::Value> ModuleSystem::GetSource(const std::string& module_name) {
  v8::HandleScope handle_scope;
  if (!source_map_->Contains(module_name))
    return v8::Undefined();
  return handle_scope.Close(source_map_->GetSource(module_name));
}

v8::Handle<v8::Value> ModuleSystem::RequireNative(const v8::Arguments& args) {
  CHECK_EQ(1, args.Length());
  std::string native_name = *v8::String::AsciiValue(args[0]->ToString());
  return RequireNativeFromString(native_name);
}

v8::Handle<v8::Value> ModuleSystem::RequireNativeFromString(
    const std::string& native_name) {
  if (natives_enabled_ == 0) {
    // HACK: if in test throw exception so that we can test the natives-disabled
    // logic; however, under normal circumstances, this is programmer error so
    // we could crash.
    if (exception_handler_)
      return v8::ThrowException(v8::String::New("Natives disabled"));
    console::Fatal(v8::Context::GetCalling(),
                   "Natives disabled for requireNative(" + native_name + ")");
    return v8::Undefined();
  }

  if (overridden_native_handlers_.count(native_name) > 0u)
    return RequireForJsInner(v8::String::New(native_name.c_str()));

  NativeHandlerMap::iterator i = native_handler_map_.find(native_name);
  if (i == native_handler_map_.end()) {
    console::Fatal(
        v8::Context::GetCalling(),
        "Couldn't find native for requireNative(" + native_name + ")");
    return v8::Undefined();
  }
  return i->second->NewInstance();
}

v8::Handle<v8::String> ModuleSystem::WrapSource(v8::Handle<v8::String> source) {
  v8::HandleScope handle_scope;
  v8::Handle<v8::String> left = v8::String::New(
      "(function(require, requireNative, exports) {'use strict';");
  v8::Handle<v8::String> right = v8::String::New("\n})");
  return handle_scope.Close(
      v8::String::Concat(left, v8::String::Concat(source, right)));
}

}  // extensions