utils/fix-proto: conditionally polyfill support for __proto__

addon/utils/fix-proto.js

@@ -0,0 +1,76 @@
+/**
+ * @module Utils
+ * @private
+ */
+
+/**
+ * Internet Explorer <= 10 has no support for `__proto__`.
+ * This conditional polyfill works around that, so that static methods like
+ * `reopen` may be used. There are some caveats though.
+ *
+ * For more information, please see: [Issue #436 (comment)][436]
+ *
+ * [436]: https://github.com/offirgolan/ember-light-table/issues/436#issuecomment-310138868
+ *
+ * @class fixProto
+ */
+
+/**
+ * Wether or not this environment supports `__proto__`.
+ * IE <= 10 is known to not support it-
+ *
+ * More information on `__proto__`:
+ *
+ *   https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/proto
+ *
+ * @const isProtoSupported
+ * @type {Boolean}
+ * @readOnly
+ */
+export const isProtoSupported = ({ __proto__: [] }) instanceof Array;
+
+/**
+ * Assigns all properties of `defaults` to `obj`, if they are not already
+ * defined on `obj`. This means that `obj` is mutated in place.
+ *
+ * Taken from:
+ *
+ *   https://github.com/babel/babel/blob/64eafad472ebac6333671fff65a9669739e6cd88/packages/babel-helpers/src/helpers.js#L287-L299
+ *
+ * @method defaults
+ * @param  {Object} obj      The object to assign the default properties to
+ * @param  {Object} defaults The object that provides all default properties to
+ *                           be assigned
+ * @return {Object}          The `obj` that was passed in
+ */
+export function defaults(obj, defaults) {
+  const keys = Object.getOwnPropertyNames(defaults);
+  for (let i = 0; i < keys.length; i++) {
+    const key = keys[i];
+    const value = Object.getOwnPropertyDescriptor(defaults, key);
+    if (value && value.configurable && obj[key] === undefined) {
+      Object.defineProperty(obj, key, value);
+    }
+  }
+  return obj;
+}
+
+/**
+ * Conditionally attempt to polyfill support for `__proto__` in environments
+ * that do not support it.
+ *
+ * If `__proto__` is not supported, this function assigns all properties and
+ * methods pf `Class.__proto__` to `Class` itself.
+ *
+ * @method fixProto
+ * @param  {Function} Class The base class
+ * @return {Function}       The `Class` that was passed in
+ */
+export default function fixProto(Class) {
+  if (isProtoSupported) {
+    return;
+  }
+
+  // https://github.com/babel/babel/tree/64eafad472ebac6333671fff65a9669739e6cd88/packages/babel-plugin-transform-proto-to-assign#example
+  return defaults(Class, Class.__proto__);
+}