Refactor runtime into libraries, better type reps

lib/runtime/js_utils.js

+// 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.
+
+/* This library defines a set of general javascript utilities for us

[Jennifer Messerly, 2015/06/12 20:12:49]

btw, I just noticed this library could be more tightly scoped. Most of this
stuff is JS reflection, so maybe `js_reflect` ? ...  There's a bit about assert
and throwing errors that doesn't quite fit, but that could stay here with a TODO
to pull out later if need

+ * by the Dart runtime.
+*/
+
+var js_utils;
+(function (js_utils) {
+  'use strict';
+
+  const defineProperty = Object.defineProperty;
+  js_utils.defineProperty = defineProperty;

[Jennifer Messerly, 2015/06/12 17:32:25]

hmm, not sure this is worth it. We can get all of these from Object already
right? Why move them to js_util?

[Leaf, 2015/06/12 19:52:14]

I was having a hard time remembering which of the defineXXX, getXXX, hasXXX came
from Object and which we defined on our own, so I found it easier to just export
them all from one place to reduce the load on my sorry noggin.  If you'd prefer
to import them directly though, I'll deal.

[Jennifer Messerly, 2015/06/12 20:12:49]

yeah I don't feel super strongly. Seems like it's fairly self documenting if the
top of the file says where it's imported from? These are pretty standard JS APIs
(they are on Object after all :) ) and documented on MDN:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Obje...
... we could also leave them qualified every time (e.g.
Object.getOwnPropertyNames ... ) if that helped?

Maybe we should have a different naming convention for our helpers, though... I
was sort of trying to make them feel like natural extensions to the built in JS
mirror operations.

At some point we'll move off all of these, though, since Reflect is better ...
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Obje...

Also, what the rule is for adding things here, vs using JS APIs directly? 

[Leaf, 2015/06/12 20:34:25]

My problem was in remembering where to import them from - once they were
imported into a file I was fine.  :)  I'll just suck it up and learn though -
not like we'll be changing this that often.  Fixed.

+  const getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
+  js_utils.getOwnPropertyDescriptor = getOwnPropertyDescriptor;
+  const getOwnPropertyNames = Object.getOwnPropertyNames;
+  js_utils.getOwnPropertyNames = getOwnPropertyNames;
+  const getOwnPropertySymbols = Object.getOwnPropertySymbols;
+  js_utils.getOwnPropertySymbols = getOwnPropertySymbols;
+  const hasOwnProperty = Object.prototype.hasOwnProperty;
+  js_utils.hasOwnProperty = hasOwnProperty;
+  const slice = [].slice;
+  js_utils.slice = [].slice;
+
+  /* This error indicates a bug in the runtime or the compiler.

[Jennifer Messerly, 2015/06/12 20:12:49]

/** ?

[Leaf, 2015/06/12 20:34:25]

Already fixed in last update.

+   */
+  function throwRuntimeError(message) {
+    throw Error(message);
+  }
+  js_utils.throwRuntimeError = throwRuntimeError;
+
+  function assert(condition) {
+    if (!condition) throwRuntimeError("The compiler is broken: failed assert");
+  }
+  js_utils.assert = assert;
+
+  function getOwnNamesAndSymbols(obj) {
+    return getOwnPropertyNames(obj).concat(getOwnPropertySymbols(obj));
+  }
+  js_utils.getOwnNamesAndSymbols = getOwnNamesAndSymbols;
+
+  function safeGetOwnProperty(obj, name) {
+    let desc = getOwnPropertyDescriptor(obj, name);
+    if (desc) return desc.value;
+  }
+  js_utils.safeGetOwnProperty = safeGetOwnProperty;
+
+  /**
+   * Defines a lazy property.
+   * After initial get or set, it will replace itself with a value property.
+   */
+  // TODO(jmesserly): is this the best implementation for JS engines?
+  // TODO(jmesserly): reusing descriptor objects has been shown to improve
+  // performance in other projects (e.g. webcomponents.js ShadowDOM polyfill).
+  function defineLazyProperty(to, name, desc) {
+    let init = desc.get;
+    let writable = !!desc.set;
+    function lazySetter(value) {
+      defineProperty(to, name, { value: value, writable: writable });
+    }
+    function lazyGetter() {
+      // Clear the init function to detect circular initialization.
+      let f = init;
+      if (f === null) throwRuntimeError('circular initialization for field ' + name);

[Jennifer Messerly, 2015/06/12 17:32:25]

long line

[Leaf, 2015/06/12 19:52:14]

Done.

+      init = null;
+
+      // Compute and store the value.
+      let value = f();
+      lazySetter(value);
+      return value;
+    }
+    desc.get = lazyGetter;
+    desc.configurable = true;
+    if (writable) desc.set = lazySetter;
+    defineProperty(to, name, desc);
+  }
+  js_utils.defineLazyProperty = defineLazyProperty;
+
+  function defineLazy(to, from) {
+    for (let name of getOwnNamesAndSymbols(from)) {
+      defineLazyProperty(to, name, getOwnPropertyDescriptor(from, name));
+    }
+  }
+  js_utils.defineLazy = defineLazy;
+
+  function defineMemoizedGetter(obj, name, get) {
+    let cache = null;
+    function getter() {
+      if (cache != null) return cache;
+      cache = get();
+      get = null;
+      return cache;
+    }
+    defineProperty(obj, name, {get: getter, configurable: true});
+  }
+  js_utils.defineMemoizedGetter = defineMemoizedGetter;
+
+  function copyTheseProperties(to, from, names) {
+    for (let name of names) {
+      defineProperty(to, name, getOwnPropertyDescriptor(from, name));
+    }
+    return to;
+  }
+  js_utils.copyTheseProperties = copyTheseProperties;
+
+  /**
+   * Copy properties from source to destination object.
+   * This operation is commonly called `mixin` in JS.
+   */
+  function copyProperties(to, from) {
+    return copyTheseProperties(to, from, getOwnNamesAndSymbols(from));
+  }
+  js_utils.copyProperties = copyProperties;
+
+})(js_utils || (js_utils = {}));