Convert dart_utils.js to input_sdk/lib/_internal/utils.dart (#310)

tool/input_sdk/private/utils.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library dart._utils;
+
+import 'dart:_foreign_helper' show JS;
+
+/// This library defines a set of general javascript utilities for us
+/// by the Dart runtime.
+
+const defineProperty = JS('', 'Object.defineProperty');
+const getOwnPropertyDescriptor = JS('', 'Object.getOwnPropertyDescriptor');
+const getOwnPropertyNames = JS('', 'Object.getOwnPropertyNames');
+const getOwnPropertySymbols = JS('', 'Object.getOwnPropertySymbols');
+
+const hasOwnProperty = JS('', 'Object.prototype.hasOwnProperty');
+
+// TODO(ochafik): Add ES6 class syntax support to JS intrinsics to avoid this.

[Jennifer Messerly, 2015/11/30 19:00:03]

ah, yeah, good idea :)

+const StrongModeError = JS('', '''(function() {
+  function StrongModeError(message) {
+    Error.call(this);
+    this.message = message;
+  };
+  Object.setPrototypeOf(StrongModeError.prototype, Error.prototype);
+  return StrongModeError;
+})()''');
+
+/// This error indicates a strong mode specific failure.
+void throwStrongModeError(message) => JS('', '''(function() {

[Jennifer Messerly, 2015/11/30 19:00:03]

should we explicitly pass in "message"? The current usage will work in our
compiler, but the reason dart2js uses "#" is so they can rename things when they
minify. Maybe it will never be an issue for us... I'm not sure.

[ochafik, 2015/12/01 14:41:03]

Now passing args with the `foo(x) => JS('', '((x) => ...)(#)', x)` pattern you
suggested :-)

+  throw new StrongModeError(message);
+})()''');
+
+/// This error indicates a bug in the runtime or the compiler.
+void throwInternalError(message) => JS('', '''(function() {
+  throw Error(message);
+})()''');
+
+void assert_(bool condition) => JS('', '''(function() {
+  if (!condition) throwInternalError("The compiler is broken: failed assert");
+})()''');
+
+getOwnNamesAndSymbols(obj) => JS('', '''(function() {
+  return getOwnPropertyNames(obj).concat(getOwnPropertySymbols(obj));
+})()''');
+
+safeGetOwnProperty(obj, name) => JS('', '''(function() {
+  let desc = getOwnPropertyDescriptor(obj, name);

[Jennifer Messerly, 2015/11/30 19:00:03]

I wonder if some of these could be written in Dart? Or is the idea to just start
off with a mostly automatic transform?

[ochafik, 2015/12/01 14:41:03]

Yes definitely, I would expect more "idiomatic" refactorings once we have
something that works. Left a TODO at the top of the file.

+  if (desc) return desc.value;
+})()''');
+
+/// Defines a lazy property.
+/// After initial get or set, it will replace itself with a value property.
+// TODO(jmesserly): reusing descriptor objects has been shown to improve
+// performance in other projects (e.g. webcomponents.js ShadowDOM polyfill).
+defineLazyProperty(to, name, desc) => JS('', '''(function() {
+  let init = desc.get;
+    let value = null;
+
+    function lazySetter(x) {
+      init = null;
+      value = x;
+    }
+    function circularInitError() {
+      throwInternalError('circular initialization for field ' + name);
+    }
+    function lazyGetter() {
+      if (init == null) return value;
+
+      // Compute and store the value, guarding against reentry.
+      let f = init;
+      init = circularInitError;
+      lazySetter(f());
+      return value;
+    }
+    desc.get = lazyGetter;
+    desc.configurable = true;
+    if (desc.set) desc.set = lazySetter;
+    return defineProperty(to, name, desc);
+})()''');
+
+void defineLazy(to, from) => JS('', '''(function() {
+  for (let name of getOwnNamesAndSymbols(from)) {
+    defineLazyProperty(to, name, getOwnPropertyDescriptor(from, name));
+  }
+})()''');
+
+defineMemoizedGetter(obj, name, getter) => JS('', '''(function() {
+  return defineLazyProperty(obj, name, {get: getter});
+})()''');
+
+copyTheseProperties(to, from, names) => JS('', '''(function() {
+  for (let name of names) {
+    defineProperty(to, name, getOwnPropertyDescriptor(from, name));
+  }
+  return to;
+})()''');
+
+/// Copy properties from source to destination object.
+/// This operation is commonly called `mixin` in JS.
+copyProperties(to, from) => JS('', '''(function() {
+  return copyTheseProperties(to, from, getOwnNamesAndSymbols(from));
+})()''');
+
+/// Exports from one Dart module to another.
+export_(to, from, show, hide) => JS('', '''(function() {
+  if (show == void 0) {
+    show = getOwnNamesAndSymbols(from);
+  }
+  if (hide != void 0) {
+    var hideMap = new Set(hide);
+    show = show.filter((k) => !hideMap.has(k));
+  }
+  return copyTheseProperties(to, from, show);
+})()''');