Add an option to remove reflect-metadata polyfills from prod bundle

[IgorMinar]

Bug Report or Feature Request (mark with an x)

- [x] feature request

Versions.

@angular/cli: 1.0.3
node: 6.9.5
os: darwin x64
@angular/animations: 4.2.0-beta.1
@angular/common: 4.2.0-beta.1
@angular/compiler: 4.2.0-beta.1
@angular/core: 4.2.0-beta.1
@angular/forms: 4.2.0-beta.1
@angular/http: 4.2.0-beta.1
@angular/material: 2.0.0-beta.4
@angular/platform-browser: 4.2.0-beta.1
@angular/platform-browser-dynamic: 4.2.0-beta.1
@angular/platform-server: 4.2.0-beta.1
@angular/router: 4.2.0-beta.1
@angular/service-worker: 1.0.0-beta.13
@angular/cli: 1.0.3
@angular/compiler-cli: 4.2.0-beta.1

Desired functionality.

reflect-metadata is a sizible chunk of code that slows down the critical path in production mode. It's only needed in the JIT (dev) mode (however we want to drop the need for in from core as well).

Currently there is no way to include the polyfill only for dev bundles. I tried using environment.ts but that gets loaded too late after the reflect api is already used by the app code.

It would be great to have a way to either strip the polyfill or have an alternative entry path for production polyfills.

[IgorMinar]

I ended up implementing this via the following hack:

diff --git a/aio/src/environments/environment.ts b/aio/src/environments/environment.ts
index 69c1f7c8bd2..165a718f559 100644
--- a/aio/src/environments/environment.ts
+++ b/aio/src/environments/environment.ts
@@ -3,6 +3,15 @@
 // `ng build --env=prod` then `environment.prod.ts` will be used instead.
 // The list of which env maps to which file can be found in `angular-cli.json`.
 
+
+// Reflect.metadata polyfill is only needed in the JIT/dev mode.
+//
+// In order to load these polyfills early enough (before app code), polyfill.ts imports this file to
+// to change the order in the final bundle.
+import 'core-js/es6/reflect';
+import 'core-js/es7/reflect';
+
+
 export const environment = {
   gaId: 'UA-8594346-26', // Staging site
   production: false
diff --git a/aio/src/polyfills.ts b/aio/src/polyfills.ts
index 53bdaf1b864..1e6698d2160 100644
--- a/aio/src/polyfills.ts
+++ b/aio/src/polyfills.ts
@@ -40,9 +40,8 @@
 // import 'web-animations-js';  // Run `npm install --save web-animations-js`.
 
 
-/** Evergreen browsers require these. **/
-import 'core-js/es6/reflect';
-import 'core-js/es7/reflect';
+/** HACK: force import of environment.ts/environment.prod.ts to load env specific polyfills */
+import './environments/environment';
 
 
 /** ALL Firefox browsers require the following to support `@angular/animation`. **/

works fine, but it's uglify and not obvious that this is what you should do to get rid of the polyfills.

[dominique-mueller]

While the solution above works pretty well, be aware that polyfills might end up twice in your bundles - one time in the polyfills bundle, and the second time in the vendor bundle (because environment is part of vendor).

I've discovered this using the webpack-bundle-analyzer, and fixed it by setting the polyfills attribute in the .angular-cli.json file to an empty string (meaning that, consequently, no polyfills bundle will be emitted now).

[dominique-mueller]

Instead of doing this via different files, I'm wondering if this could also be achieved using Webpack ...

[dominique-mueller]

Seems that patching the @angular\cli\models\webpack-configs\production.js file with the following content works:

externals: {
  'core-js/es6/reflect': 'reflect',
  'core-js/es7/reflect': 'reflect'
},

Or even shorter:

externals: /^core-js\/(es6|es7)\/reflect$/,

Wrote a short NodeJS script which patches internal files on postinstall, similar to moment/moment#2416 (comment):

console.log( 'Modifying Angular CLI configuration ...' );
fs.readFile( './node_modules/@angular/cli/models/webpack-configs/production.js', 'utf-8', ( error, fileContent ) => {

  // Add core-js reflect patch
  console.log( '  -> Adding core-js reflect fix ...' );
  const reflectPolyfillsFix = `externals: /^core-js\\/(es6|es7)\\/reflect$/,`;
  if ( fileContent.indexOf( reflectPolyfillsFix ) === -1 ) {
    const uniqueContentToReplace = 'return {';
    fileContent = fileContent.replace( uniqueContentToReplace, `${ uniqueContentToReplace }\n        ${ reflectPolyfillsFix }` );
    console.log( '     Done.' )
  } else {
    console.log( '     Nothing to do.' );
  }

  // Write modified file
  fs.writeFile( './node_modules/@angular/cli/models/webpack-configs/production.js', fileContent, 'utf-8', ( error ) => {
    console.log( 'Done!' );
  } );

} );

[IgorMinar]

this has been implemented in v7