Merge pull request rust-lang#331 from Gaurav0/deprecate_globals_resolver

Deprecate Globals Resolver

Author: rwjblue

text/0331-deprecate-globals-resolver.md

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+- Start Date: 2018-05-08
+- RFC PR: https://github.com/emberjs/rfcs/pull/331
+- Ember Issue: (leave this empty)
+
+# Summary
+
+Deprecate all use of:
+
+- Ember Globals Resolver (looks up a class via a global namespace such as "App")
+- Creation of a Global Namespace (`var App = Ember.Namespace.create();`)
+- Ember.TEMPLATES array
+- <script type="text/handlebars" data-template-name="path/to/template">
+
+Use of any of the above should trigger a deprecation warning, with a target
+of version 4.0
+
+# Motivation
+
+Over the past years we have transitioned to using Ember-CLI as the main way
+to compile Ember apps. The globals resolver is a holdover and primarily
+facilitates use of Ember without Ember-CLI.
+
+# The Globals Resolver
+
+For those who are not aware, the globals resolver is available via `@ember/globals-resolver` or
+`Ember.DefaultResolver`. For more information, see the
+[api](https://www.emberjs.com/api/ember/release/classes/GlobalsResolver/properties).
+Using it looks like the following:
+
+```js
+// app.js
+var App = Ember.Application.create();
+
+App.Router.map(function() {
+  this.route('about');
+});
+
+App.AboutRoute = Ember.Route.extend({
+  model: function() {
+    return ['red', 'yellow', 'blue'];
+  }
+});
+```
+
+```html
+// index.html
+<script type="text/x-handlebars" data-template-name="about">
+  <ul>
+    {{#each model as |item|}}
+      <li>{{item}}</li>
+    {{/each}}
+  </ul>
+</script>
+```
+
+# Implementation Details
+
+One small detail required to implement this RFC: ember-cli's own default resolver,
+[ember-resolver](https://github.com/ember-cli/ember-resolver)
+currently still extends from the globals resolver.
+In order to implement this RFC, the ember-cli resolver will need to be changed
+so that it does *not* extend from the globals resolver, or otherwise ember-cli users
+will get a deprecation warning as well.
+However, changing the base class of the ember cli classic resolver is a breaking change,
+so prior to ember/ember-cli version 4.0 we need to take another step.
+In the ember-cli classic resolver, deprecate any runtime calls where there is fallback to the globals mode resolver. This would be a deprecation in ember-cli's resolver. We could bump a major version of ember-cli-resolver removing the base class and release it in ember-cli after an LTS of ember-cli.
+
+# Transition Path
+
+Primarily, the transition path is to recommend using Ember-CLI.
+
+During the 3.x timeframe, it MAY become increasingly difficult to use this old functionality.
+For example, with the release of 3.0, we already stopped publishing builds that support
+globals mode. Here are some of the changes that have impacted or may soon impact users of globals mode:
+
+## Impact of ES6 modules
+
+Users of ES6 modules must use their own build tooling to convert them to named AMD modules via Babel.
+No support is provided for &lt;script type="module"&gt; at this time, although that may change.
+
+## Impact of New Module Imports
+
+Globals based apps are only able to use new module imports via the polyfill available at
+https://github.com/ember-cli/babel-plugin-ember-modules-api-polyfill No build support for this is provided.
+
+## Impact of not publishing globals builds
+
+It is necessary to get a globals build of Ember.js from the npm package now that globals builds
+are no longer published to S3, builds.emberjs.com, and CDNs.
+
+## Impact of not Generating a Globals Build in Ember.js Package
+
+At some point during the 3.x cycle, it may be that we no longer publish a globals build in the
+npm package. At that point, it may become necessary to use Ember-CLI to generate a globals build
+of Ember.js
+
+## Impact of Package Splitting
+
+Work has started on package splitting. It is likely that the globals resolver may not be included
+in a default partial build of Ember.js and may be moved to its own package for easy removal.
+
+## Impact of Tree Shaking
+
+If the globals resolver is moved to a separate package, it will likely not be included in a build
+of Ember.js by default unless tree shaking is turned off.
+
+# How We Teach This
+
+We already do teach this and don't teach the globals resolver. No changes required here.
+
+## Deprecation Guide
+
+A draft deprecation guide has been pull requested at https://github.com/ember-learn/deprecation-app/pull/155
+
+# Drawbacks
+
+A drawback is that people may want alternate build tooling to Ember-CLI.
+We have mitigated this by openly publishing the ember-cli resolver and all parts of the
+ember-cli ecosystem under the MIT license.
+Alternate build tooling may simply use this open source code to build a competing
+infrastructure to ember-cli.
+
+# Alternatives
+
+Without doing this, we will have to continue to ship and maintain this rarely used functionality.
+We don't believe this is a reasonable alternative.
+
+# Unresolved questions
+
+There has never been a transition guide for transitioning an old codebase to Ember-CLI.
+Do we want to create one at this late date?