[FEAT] Implements Decorators

This PR refactors the Descriptor system in Ember metal, mostly replacing
it with a Decorator system instead. `defineProperty` has been updated to
apply decorators following the currently implemented spec. This means
that the value returned by `computed` goes through the exact same flow
when applied as a decorator using decorator syntax, and applied using
classic syntax.

.eslintrc.js

@@ -2,6 +2,7 @@ const path = require('path');
 
 module.exports = {
   root: true,
+  parser: 'babel-eslint',
   extends: [
     'eslint:recommended',
     'prettier',

broccoli/packages.js

@@ -16,6 +16,7 @@ const WriteFile = require('broccoli-file-creator');
 const StringReplace = require('broccoli-string-replace');
 const GlimmerTemplatePrecompiler = require('./glimmer-template-compiler');
 const VERSION_PLACEHOLDER = /VERSION_STRING_PLACEHOLDER/g;
+const transfromBabelPlugins = require('./transforms/transform-babel-plugins');
 
 const debugTree = BroccoliDebug.buildDebugCallback('ember-source');
 
@@ -83,6 +84,13 @@ module.exports.getPackagesES = function getPackagesES() {
     exclude: ['**/*.ts'],
   });
 
+  // tsc / typescript handles decorators and class properties on its own
+  // so for non ts, transpile the proposal features (decorators, etc)
+  let transpiledProposals = debugTree(
+    transfromBabelPlugins(debugTree(nonTypeScriptContents, `get-packages-es:babel-plugins:input`)),
+    `get-packages-es:babel-plugins:output`
+  );
+
   let typescriptContents = new Funnel(debuggedCompiledTemplatesAndTypeScript, {
     include: ['**/*.ts'],
   });
@@ -95,7 +103,7 @@ module.exports.getPackagesES = function getPackagesES() {
 
   let debuggedCompiledTypescript = debugTree(typescriptCompiled, `get-packages-es:ts:output`);
 
-  let mergedFinalOutput = new MergeTrees([nonTypeScriptContents, debuggedCompiledTypescript], {
+  let mergedFinalOutput = new MergeTrees([transpiledProposals, debuggedCompiledTypescript], {
     overwrite: true,
   });
 

broccoli/transforms/transform-babel-plugins.js

@@ -0,0 +1,13 @@
+const Babel = require('broccoli-babel-transpiler');
+
+module.exports = function(tree) {
+  let options = {
+    sourceMaps: true,
+    plugins: [
+      ['@babel/plugin-proposal-decorators', { decoratorsBeforeExport: true, legacy: false }],
+      ['@babel/plugin-proposal-class-properties'],
+    ],
+  };
+
+  return new Babel(tree, options);
+};

jsconfig.json

@@ -0,0 +1,11 @@
+{
+  "compilerOptions": {
+    "module": "commonjs",
+    "target": "es2016",
+    "experimentalDecorators": true
+  },
+  "exclude": [
+    "node_modules",
+    "**/node_modules/*"
+  ]
+}

package.json

@@ -77,6 +77,8 @@
   },
   "devDependencies": {
     "@babel/helper-module-imports": "^7.0.0",
+    "@babel/plugin-proposal-class-properties": "^7.2.1",
+    "@babel/plugin-proposal-decorators": "^7.2.0",
     "@babel/plugin-transform-arrow-functions": "^7.2.0",
     "@babel/plugin-transform-block-scoping": "^7.2.0",
     "@babel/plugin-transform-classes": "^7.2.2",
@@ -101,6 +103,7 @@
     "@types/rsvp": "^4.0.2",
     "auto-dist-tag": "^1.0.0",
     "aws-sdk": "^2.395.0",
+    "babel-eslint": "^10.0.1",
     "babel-plugin-debug-macros": "^0.3.0",
     "babel-plugin-filter-imports": "^2.0.4",
     "babel-plugin-module-resolver": "^3.1.3",

packages/@ember/-internals/meta/index.ts

@@ -1,8 +1,6 @@
 export {
   counters,
   deleteMeta,
-  descriptorFor,
-  isDescriptor,
   Meta,
   meta,
   MetaCounters,

packages/@ember/-internals/meta/lib/meta.ts

@@ -978,48 +978,6 @@ if (DEBUG) {
   meta._counters = counters;
 }
 
-/**
-  Returns the CP descriptor assocaited with `obj` and `keyName`, if any.
-
-  @method descriptorFor
-  @param {Object} obj the object to check
-  @param {String} keyName the key to check
-  @return {Descriptor}
-  @private
-*/
-export function descriptorFor(obj: object, keyName: string, _meta?: Meta | null) {
-  assert('Cannot call `descriptorFor` on null', obj !== null);
-  assert('Cannot call `descriptorFor` on undefined', obj !== undefined);
-  assert(
-    `Cannot call \`descriptorFor\` on ${typeof obj}`,
-    typeof obj === 'object' || typeof obj === 'function'
-  );
-
-  let meta = _meta === undefined ? peekMeta(obj) : _meta;
-
-  if (meta !== null) {
-    return meta.peekDescriptors(keyName);
-  }
-}
-
-/**
-  Check whether a value is a CP descriptor.
-
-  @method isDescriptor
-  @param {any} possibleDesc the value to check
-  @return {boolean}
-  @private
-*/
-export function isDescriptor(possibleDesc: any | undefined | null): boolean {
-  // TODO make this return `possibleDesc is Descriptor`
-  return (
-    possibleDesc !== undefined &&
-    possibleDesc !== null &&
-    typeof possibleDesc === 'object' &&
-    possibleDesc.isDescriptor === true
-  );
-}
-
 export { counters };
 
 function indexOfListener(

packages/@ember/-internals/metal/index.ts

@@ -1,4 +1,4 @@
-export { default as computed, ComputedProperty, _globalsComputed } from './lib/computed';
+export { default as computed, _globalsComputed, ComputedProperty } from './lib/computed';
 export { getCacheFor, getCachedValueFor, peekCacheFor } from './lib/computed_cache';
 export { default as alias } from './lib/alias';
 export { deprecateProperty } from './lib/deprecate_property';
@@ -28,7 +28,13 @@ export {
   overrideChains,
   PROPERTY_DID_CHANGE,
 } from './lib/property_events';
-export { defineProperty, Descriptor } from './lib/properties';
+export { defineProperty } from './lib/properties';
+export {
+  descriptorForProperty,
+  isComputedDecorator,
+  setComputedDecorator,
+  nativeDescDecorator,
+} from './lib/decorator';
 export { watchKey, unwatchKey } from './lib/watch_key';
 export { ChainNode, finishChains, removeChainWatcher } from './lib/chains';
 export { watchPath, unwatchPath } from './lib/watch_path';
@@ -40,10 +46,9 @@ export { default as expandProperties } from './lib/expand_properties';
 
 export { addObserver, removeObserver } from './lib/observer';
 export { Mixin, aliasMethod, mixin, observer, applyMixin } from './lib/mixin';
-export { default as InjectedProperty } from './lib/injected_property';
+export { default as inject, DEBUG_INJECTION_FUNCTIONS } from './lib/injected_property';
 export { setHasViews, tagForProperty, tagFor, markObjectAsDirty } from './lib/tags';
 export { default as runInTransaction, didRender, assertNotRendered } from './lib/transaction';
-export { default as descriptor } from './lib/descriptor';
 export { tracked } from './lib/tracked';
 
 export {

packages/@ember/-internals/metal/lib/alias.ts

@@ -2,25 +2,50 @@ import { Meta, meta as metaFor } from '@ember/-internals/meta';
 import { inspect } from '@ember/-internals/utils';
 import { assert } from '@ember/debug';
 import EmberError from '@ember/error';
-import { ComputedProperty } from './computed';
 import { getCachedValueFor, getCacheFor } from './computed_cache';
 import {
   addDependentKeys,
-  DescriptorWithDependentKeys,
+  ComputedDescriptor,
+  Decorator,
+  descriptorForDecorator,
+  makeComputedDecorator,
   removeDependentKeys,
-} from './dependent_keys';
-import { defineProperty, Descriptor } from './properties';
+} from './decorator';
+import { defineProperty } from './properties';
 import { get } from './property_get';
 import { set } from './property_set';
 
 const CONSUMED = Object.freeze({});
 
-export default function alias(altKey: string): AliasedProperty {
-  return new AliasedProperty(altKey);
+export type AliasDecorator = Decorator & PropertyDecorator & AliasDecoratorImpl;
+
+export default function alias(altKey: string): AliasDecorator {
+  return makeComputedDecorator(new AliasedProperty(altKey), AliasDecoratorImpl) as AliasDecorator;
+}
+
+class AliasDecoratorImpl {
+  readOnly(this: Decorator) {
+    descriptorForDecorator(this).readOnly();
+    return this;
+  }
+
+  oneWay(this: Decorator) {
+    descriptorForDecorator(this).oneWay();
+    return this;
+  }
+
+  meta(this: Decorator, meta?: any): any {
+    let prop = descriptorForDecorator(this);
+
+    if (arguments.length === 0) {
+      return prop._meta || {};
+    } else {
+      prop._meta = meta;
+    }
+  }
 }
 
-export class AliasedProperty extends Descriptor implements DescriptorWithDependentKeys {
-  readonly _dependentKeys: string[];
+export class AliasedProperty extends ComputedDescriptor {
   readonly altKey: string;
 
   constructor(altKey: string) {
@@ -29,9 +54,10 @@ export class AliasedProperty extends Descriptor implements DescriptorWithDepende
     this._dependentKeys = [altKey];
   }
 
-  setup(obj: object, keyName: string, meta: Meta): void {
+  setup(obj: object, keyName: string, propertyDesc: PropertyDescriptor, meta: Meta): void {
     assert(`Setting alias '${keyName}' on self`, this.altKey !== keyName);
-    super.setup(obj, keyName, meta);
+    super.setup(obj, keyName, propertyDesc, meta);
+
     if (meta.peekWatching(keyName) > 0) {
       this.consume(obj, keyName, meta);
     }
@@ -74,14 +100,12 @@ export class AliasedProperty extends Descriptor implements DescriptorWithDepende
     return set(obj, this.altKey, value);
   }
 
-  readOnly(): this {
+  readOnly(): void {
     this.set = AliasedProperty_readOnlySet;
-    return this;
   }
 
-  oneWay(): this {
+  oneWay(): void {
     this.set = AliasedProperty_oneWaySet;
-    return this;
   }
 }
 
@@ -94,7 +118,3 @@ function AliasedProperty_oneWaySet(obj: object, keyName: string, value: any): an
   defineProperty(obj, keyName, null);
   return set(obj, keyName, value);
 }
-
-// Backwards compatibility with Ember Data.
-(AliasedProperty.prototype as any)._meta = undefined;
-(AliasedProperty.prototype as any).meta = ComputedProperty.prototype.meta;

packages/@ember/-internals/metal/lib/chains.ts

@@ -1,5 +1,6 @@
-import { descriptorFor, Meta, meta as metaFor, peekMeta } from '@ember/-internals/meta';
+import { Meta, meta as metaFor, peekMeta } from '@ember/-internals/meta';
 import { getCachedValueFor } from './computed_cache';
+import { descriptorForProperty } from './decorator';
 import { eachProxyFor } from './each_proxy';
 import { get } from './property_get';
 import { unwatchKey, watchKey } from './watch_key';
@@ -9,7 +10,7 @@ function isObject(obj: any): obj is object {
 }
 
 function isVolatile(obj: any, keyName: string, meta?: Meta | null): boolean {
-  let desc = descriptorFor(obj, keyName, meta);
+  let desc = descriptorForProperty(obj, keyName, meta);
   return !(desc !== undefined && desc._volatile === false);
 }