Implement Asynchronous Module Definition API for Mojo

gin/modules/module_registry.cc

Index: gin/modules/module_registry.cc
diff --git a/gin/modules/module_registry.cc b/gin/modules/module_registry.cc
new file mode 100644
index 0000000000000000000000000000000000000000..63849304366e3e51643ed30c9b47179ab2493b01
--- /dev/null
+++ b/gin/modules/module_registry.cc
@@ -0,0 +1,188 @@
+// Copyright 2013 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 "gin/modules/module_registry.h"
+
+#include <assert.h>
+#include <string>
+#include <vector>
+#include "gin/arguments.h"
+#include "gin/converter.h"
+#include "gin/per_isolate_data.h"
+#include "gin/wrapper_info.h"
+
+using v8::Handle;
+using v8::Isolate;
+using v8::ObjectTemplate;
+
+namespace gin {
+
+struct PendingModule {
+  PendingModule();
+  ~PendingModule();
+
+  std::string id;
+  std::vector<std::string> dependencies;
+  v8::Persistent<v8::Value> factory;
+};
+
+namespace {
+
+void Define(const v8::FunctionCallbackInfo<v8::Value>& info) {
+  Arguments args(info);
+
+  if (!info.Length())
+    return args.ThrowTypeError("At least one argument is required.");
+
+  std::string id;
+  std::vector<std::string> dependencies;
+  Handle<v8::Value> factory;
+
+  if (args.PeekNext()->IsString())
+    args.GetNext(&id);
+  if (args.PeekNext()->IsArray())
+    args.GetNext(&dependencies);
+  if (!args.GetNext(&factory))

[Aaron Boodman, 2013/11/15 18:56:06]

"Factory" seems like a weird name for the function that defines the module. What
about "code"? Also, you should GetNext() into a v8::Function so that an error
results if the caller passes the wrong type.

[abarth-chromium, 2013/11/15 19:13:37]

In AMD, you can either supply a function or an object literal directly.  For
example, this is a valid module:

define("myconstants", {
  "fruit": "banana",
});

I guess I can see the appeal of that, but it does mean there are a few odd cases
to deal with here and there.

The name "factory" comes from the AMD spec:

https://github.com/amdjs/amdjs-api/wiki/AMD#define-function-

We don't need to use the names from the spec if you'd prefer another name.

+    return args.ThrowError();
+
+  PendingModule* pending = new PendingModule;
+  pending->id = id;
+  pending->dependencies = dependencies;
+  pending->factory.Reset(args.isolate(), factory);
+
+  ModuleRegistry* registry =
+      ModuleRegistry::From(args.isolate()->GetCurrentContext());
+  registry->AddPendingModule(args.isolate(), pending);
+}
+
+WrapperInfo g_wrapper_info = {};
+
+v8::Local<v8::FunctionTemplate> GetDefineTemplate(v8::Isolate* isolate) {
+  PerIsolateData* data = PerIsolateData::From(isolate);
+  v8::Local<v8::FunctionTemplate> templ = data->GetFunctionTemplate(
+      &g_wrapper_info);
+  if (templ.IsEmpty()) {
+    templ = v8::FunctionTemplate::New(Define);
+    templ->SetLength(3);

[Aaron Boodman, 2013/11/15 18:56:06]

I don't think this is really necessary, fwiw.

[abarth-chromium, 2013/11/15 19:13:37]

Ok, I'll remove it.  It's visible in JavaScript, but we can return the default
value.

+    data->SetFunctionTemplate(&g_wrapper_info, templ);
+  }
+  return templ;
+}
+
+}  // namespace gin
+
+
+PendingModule::PendingModule() {
+}
+
+PendingModule::~PendingModule() {
+  factory.Reset();
+}
+
+ModuleRegistry::ModuleRegistry(v8::Isolate* isolate)
+    : modules_(isolate, v8::Object::New()) {
+}
+
+ModuleRegistry::~ModuleRegistry() {
+  for (PendingModuleList::iterator it = pending_modules_.begin();
+       it != pending_modules_.end(); ++it) {
+    delete *it;
+  }
+  modules_.Reset();
+}
+
+void ModuleRegistry::RegisterGlobals(v8::Isolate* isolate,
+                                     Handle<v8::ObjectTemplate> templ) {
+  templ->Set(StringToSymbol(isolate, "define"), GetDefineTemplate(isolate));
+}
+
+void ModuleRegistry::AddBuiltinModule(Isolate* isolate,
+                                      const std::string& id,
+                                      Handle<ObjectTemplate> templ) {
+  assert(!id.empty());
+  Handle<v8::Object> modules = v8::Local<v8::Object>::New(isolate, modules_);
+  modules->Set(StringToV8(isolate, id), templ->NewInstance());
+}
+
+ModuleRegistry* ModuleRegistry::From(Handle<v8::Context> context) {
+  v8::Isolate* isolate = context->GetIsolate();
+  Handle<v8::String> key = Key(isolate);
+  Handle<v8::Value> encoded = context->Global()->GetHiddenValue(key);

[Aaron Boodman, 2013/11/15 18:56:06]

Why is this variable called "encoded"?

[abarth-chromium, 2013/11/15 19:13:37]

Just because it's a pointer encoded into a v8 object.  I can call it
external_value or encoded_pointer or whatever you like if you think that would
be clearer.

+  if (encoded.IsEmpty() || !encoded->IsExternal()) {
+    PerContextData* data = PerContextData::From(context);
+    if (!data)
+      return NULL;
+    ModuleRegistry* registry = new ModuleRegistry(isolate);
+    context->Global()->SetHiddenValue(key, v8::External::New(registry));
+    data->AddSupplement(registry);
+    return registry;
+  }
+  Handle<v8::External> external = Handle<v8::External>::Cast(encoded);
+  return static_cast<ModuleRegistry*>(external->Value());
+}
+
+void ModuleRegistry::AddPendingModule(v8::Isolate* isolate,
+                                      PendingModule* pending) {
+  if (AttemptToLoad(isolate, pending))
+    AttemptToLoadPendingModules(isolate);
+}
+
+Handle<v8::String> ModuleRegistry::Key(v8::Isolate* isolate) {

[Aaron Boodman, 2013/11/15 18:56:06]

::GetHiddenValueKey(). Also, this could just be a helper function in an anon
namespace, doesn't need to be a method.

[abarth-chromium, 2013/11/15 19:13:37]

Will do.

+  return StringToSymbol(isolate, "::gin::ModuleRegistry");
+}
+
+void ModuleRegistry::Detach(Handle<v8::Context> context) {
+  context->Global()->SetHiddenValue(Key(context->GetIsolate()),
+                                    Handle<v8::Value>());
+}
+
+bool ModuleRegistry::AttemptToLoad(v8::Isolate* isolate,
+                                   PendingModule* pending) {
+  Handle<v8::Object> modules = v8::Local<v8::Object>::New(isolate, modules_);
+  Handle<v8::String> key = StringToV8(isolate, pending->id);
+
+  if (!pending->id.empty() && modules->HasOwnProperty(key)) {
+    // We've already loaded a module with this name. Ignore the new one.
+    delete pending;
+    return true;
+  }
+
+  size_t argc = pending->dependencies.size();
+  std::vector<Handle<v8::Value> > argv(argc);
+  for (size_t i = 0; i < argc; ++i) {
+    Handle<v8::String> key = StringToV8(isolate, pending->dependencies[i]);
+    if (!modules->HasOwnProperty(key)) {
+      pending_modules_.push_back(pending);
+      return false;
+    }
+    argv[i] = modules->Get(key);
+  }
+
+  Handle<v8::Value> module = v8::Local<v8::Value>::New(
+      isolate, pending->factory);
+
+  Handle<v8::Function> factory;
+  if (ConvertFromV8(module, &factory)) {
+    v8::Handle<v8::Object> global = isolate->GetCurrentContext()->Global();
+    module = factory->Call(global, argc, argv.data());
+    // TODO(abarth): What should we do with exceptions?
+  }
+
+  if (!pending->id.empty() && !module.IsEmpty())
+    modules->Set(key, module);
+
+  delete pending;
+  return true;
+}
+
+void ModuleRegistry::AttemptToLoadPendingModules(v8::Isolate* isolate) {
+  PendingModuleList pending_modules;
+  pending_modules.swap(pending_modules_);
+  for (PendingModuleList::iterator it = pending_modules.begin();
+       it != pending_modules.end(); ++it) {
+    AttemptToLoad(isolate, *it);
+  }
+}
+
+}  // namespace gin