[BUGFIX lts] Adds the babel-helpers injection plugin back

Helpers were no longer being externalized in our builds, which adds a
significant amount to the final payload. This adds them back into the
build.

Also fixes an issue where the template compiler was not being included
in the vendor folder for Ember.

ensure async helpers are inlined in dev

Cherry-picked from PR emberjs#18291

lib/index.js

@@ -7,6 +7,7 @@ const resolve = require('resolve');
 const concatBundle = require('./concat-bundle');
 const buildDebugMacroPlugin = require('./build-debug-macro-plugin');
 const buildStripClassCallcheckPlugin = require('./build-strip-class-callcheck-plugin');
+const injectBabelHelpers = require('./transforms/inject-babel-helpers');
 
 const isProduction = process.env.EMBER_ENV === 'production';
 
@@ -71,6 +72,10 @@ module.exports = {
     let appOptions = this.app && this.app.options;
     let babelOptions = (parentOptions || appOptions || {}).babel;
 
+    // We want to enable async/generator helpers if we are developing locally,
+    // but not for any other project.
+    let isEmberSource = this.project.name() === 'ember-source';
+
     let options = {
       'ember-cli-babel': {
         disableDebugTooling: true,
@@ -79,6 +84,7 @@ module.exports = {
       babel: Object.assign({}, babelOptions, {
         loose: true,
         plugins: [
+          injectBabelHelpers(isEmberSource),
           buildDebugMacroPlugin(!isProduction),
           [
             require.resolve('@babel/plugin-transform-block-scoping'),
@@ -157,6 +163,11 @@ module.exports = {
       files: ['jquery.js'],
     });
 
+    let templateCompiler = new Funnel(tree, {
+      destDir: 'ember',
+      include: ['ember-template-compiler.js', 'ember-template-compiler.map'],
+    });
+
     let ember;
     let targets = (this.project && this.project.targets && this.project.targets.browsers) || [];
 
@@ -178,6 +189,6 @@ module.exports = {
       });
     }
 
-    return new MergeTrees([ember, jquery]);
+    return new MergeTrees([ember, templateCompiler, jquery]);
   },
 };

lib/transforms/inject-babel-helpers.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const { addNamed } = require('@babel/helper-module-imports');
+
+function injectBabelHelpers(isEmberSource = false) {
+  function injectBabelHelpersPlugin() {
+    return {
+      pre(file) {
+        file.set('helperGenerator', function(name) {
+          if (name === 'extends') {
+            return addNamed(file.path, 'assign', '@ember/polyfills');
+          } else if (isEmberSource && name === 'asyncToGenerator') {
+            // Returning a falsy value will cause the helper to be inlined,
+            // which is fine for local tests
+            return false;
+          }
+
+          return addNamed(file.path, name, 'ember-babel');
+        });
+      },
+    };
+  }
+
+  injectBabelHelpersPlugin.baseDir = function() {
+    return 'babel-core';
+  };
+
+  return injectBabelHelpersPlugin;
+}
+
+module.exports = injectBabelHelpers;

package.json

@@ -48,6 +48,7 @@
     "test:browserstack": "node bin/run-browserstack-tests.js"
   },
   "dependencies": {
+    "@babel/helper-module-imports": "^7.0.0",
     "@babel/plugin-transform-block-scoping": "^7.4.4",
     "@babel/plugin-transform-object-assign": "^7.2.0",
     "babel-plugin-debug-macros": "^0.3.2",
@@ -69,7 +70,6 @@
     "resolve": "^1.11.1"
   },
   "devDependencies": {
-    "@babel/helper-module-imports": "^7.0.0",
     "@babel/preset-env": "^7.5.5",
     "@glimmer/compiler": "0.38.5-alpha.2",
     "@glimmer/env": "^0.1.7",