fix: Stop babel from rewriting babel helpers in core-js. (#2116)

- Prevents `@babel/plugin-transform-runtime` from rewriting babel helpers in core-js.
- Remove unneeded runtime `@babel/runtime-corejs3`

cc: #2031, #2109

Author: jakeNiemiec

CHANGELOG.md

@@ -1,5 +1,13 @@
 **Please note that Webpacker 3.1.0 and 3.1.1 have some serious bugs so please consider using either 3.0.2 or 3.2.0**
 
+## [[4.0.7]](https://github.com/rails/webpacker/compare/v4.0.6...v4.0.7) - 2019-06-03
+
+- Prevent `@babel/plugin-transform-runtime` from rewriting babel helpers in core-js. Remove unneeded runtime `@babel/runtime-corejs3` [#2116](https://github.com/rails/webpacker/pull/2116)
+  - Fix for: [#2109 Uncaught TypeError: __webpack_require__(...) is not a function](https://github.com/rails/webpacker/issues/2109): **If you are upgrading**, please check your `babel.config.js` against the [default `babel.config.js`](https://github.com/rails/webpacker/blob/master/lib/install/config/babel.config.js):
+    - `@babel/preset-env` should contain `corejs: 3` 
+    - `@babel/plugin-transform-runtime` should contain `corejs: false`
+- Removed unneeded runtime `@babel/runtime-corejs3`
+
 ## [[4.0.6]](https://github.com/rails/webpacker/compare/v4.0.5...v4.0.6) - 2019-05-30
 
 - Webpack should not be transpiled [#2111](https://github.com/rails/webpacker/pull/2111)
@@ -16,7 +24,7 @@
 
 Please see the diff
 
-### Breaking changes
+##### Breaking changes (for pre-existing apps)
 
  - [`@babel/polyfill`](https://babeljs.io/docs/en/next/babel-polyfill.html) [doesn't make it possible to provide a smooth migration path from `core-js@2` to `core-js@3`](https://github.com/zloirock/core-js/blob/master/docs/2019-03-19-core-js-3-babel-and-a-look-into-the-future.md#babelpolyfill): for this reason, it was decided to deprecate `@babel/polyfill` in favor of separate inclusion of required parts of `core-js` and `regenerator-runtime`. [#2031](https://github.com/rails/webpacker/pull/2031)
 

lib/install/config/babel.config.js

@@ -58,7 +58,7 @@ module.exports = function(api) {
         {
           helpers: false,
           regenerator: true,
-          corejs: 3
+          corejs: false
         }
       ],
       [

lib/install/examples/react/babel.config.js

@@ -64,7 +64,8 @@ module.exports = function(api) {
         require('@babel/plugin-transform-runtime').default,
         {
           helpers: false,
-          regenerator: true
+          regenerator: true,
+          corejs: false
         }
       ],
       [

package.json

@@ -21,7 +21,6 @@
     "@babel/plugin-transform-runtime": "^7.4.4",
     "@babel/preset-env": "^7.4.5",
     "@babel/runtime": "^7.4.5",
-    "@babel/runtime-corejs3": "^7.4.5",
     "babel-loader": "^8.0.6",
     "babel-plugin-dynamic-import-node": "^2.2.0",
     "babel-plugin-macros": "^2.5.0",

yarn.lock

@@ -622,14 +622,6 @@
     js-levenshtein "^1.1.3"
     semver "^5.5.0"
 
-"@babel/runtime-corejs3@^7.4.5":
-  version "7.4.5"
-  resolved "https://registry.yarnpkg.com/@babel/runtime-corejs3/-/runtime-corejs3-7.4.5.tgz#7df89702351c5fdc34b5555544fcf11b4ea7051c"
-  integrity sha512-yxHpUObdpx4zbuLJOHIZkw43E4NbWGsGH+85kRUj+VEcdtjlqI0vDcAja9mwOHqD7/4vCZp69q6eztz/sFDibQ==
-  dependencies:
-    core-js-pure "^3.0.0"
-    regenerator-runtime "^0.13.2"
-
 "@babel/runtime@^7.4.2", "@babel/runtime@^7.4.5":
   version "7.4.5"
   resolved "https://registry.yarnpkg.com/@babel/runtime/-/runtime-7.4.5.tgz#582bb531f5f9dc67d2fcb682979894f75e253f12"
@@ -1992,7 +1984,7 @@ core-js-compat@^3.1.1:
     core-js-pure "3.1.3"
     semver "^6.1.0"
 
-[email protected], core-js-pure@^3.0.0:
+[email protected]:
   version "3.1.3"
   resolved "https://registry.yarnpkg.com/core-js-pure/-/core-js-pure-3.1.3.tgz#4c90752d5b9471f641514f3728f51c1e0783d0b5"
   integrity sha512-k3JWTrcQBKqjkjI0bkfXS0lbpWPxYuHWfMMjC1VDmzU4Q58IwSbuXSo99YO/hUHlw/EB4AlfA2PVxOGkrIq6dA==