Angular 10 Upgrade - 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

WARNING in calendar.reducer.ts depends on lodash/keys. CommonJS or AMD dependencies can cause optimization bailouts.

I have added below line to my angular.json file but issue is not resolved

"allowedCommonJsDependencies": ["lodash"]

How can I fix above issue.

Answer 1

The npm package lodash itself is not an ECMAScript module and therefore produces the warning. As a result, you may have a significantly increased bundle size, as the compiler is not able to perform tree-shaking. Here is how you can get rid of the warning:

Replace with ES modulized library (recommended)

Some libraries offer ES modulized builds. In case of lodash, you can replace it with lodash-es.

Run npm install --save lodash-es.

Now replace all imports from lodash with lodash-es. Also make sure to import the library with ES import statements:

import { keys } from 'lodash-es';

This will ensure that the compiler can optimize out unused symbols from the package.

Whitelist CommonJS dependency

If there is no ES modulized build available for your library, or if you for some reason don't care, you can allow specific CommonJS dependencies in the angular.json file (this may significantly increase the bundle size of your application):

"architect": {
  "build": {
    "builder": "@angular-devkit/build-angular:browser",
    "options": {
      "allowedCommonJsDependencies": ["lodash"]
    }
  }
}

Since Angular CLI Version 10.0.1 you can use globs in allowedCommonJsDependencies. This means that if you pass lodash, the sub-paths (e.g. lodash/keys) will also be allowed.

Docs reference: https://angular.dev/tools/cli/build#configuring-commonjs-dependencies