javascript - Upgrading to Angular 10 - Fix CommonJS or AMD dependencies can cause optimization bailouts

Question

I am trying to upgrade my angular 9 app to angular 10 version, but getting below warning after the upgrade

rxjsBehaviorSubject.js depends on rxjs-compat/BehaviorSubject

Any idea how to fix this?

Answer 1

When you use a dependency that is packaged with CommonJS, it can result in larger slower applications

Starting with version 10, Angular now warns you when your build pulls in one of these bundles. If you’ve started seeing these warnings for your dependencies, let your dependency know that you’d prefer an ECMAScript module (ESM) bundle.

Here is an official documentation - Configuring CommonJS dependencies

In your angular.json file look for the build object and add

allowedCommonJsDependencies

as shown below -

"build": {
  "builder": "@angular-devkit/build-angular:browser",
  "options": {
     "allowedCommonJsDependencies": [
        "rxjs-compat",
         ... few more commonjs dependencies ... 
     ]
     ...
   }
   ...
},