This small package hooks into native Angular CLI builders. With it, you can...

• ... run code before Angular CLI invocates native builders
• ... and/or override invocations
• ... and/or run code after Angular CLI emits BuilderOutput

A few examples include

• Running eslint before ng build runs
• Using jest over jasmine when running ng test
• Starting a mock server with ng serve

First, you need to create a package of hooks. To, for example, run ESLint before ng build, add a hook to build and a before-function. The before-function can return either Observable, Promise or a sync value.

Then, to make the hook configurable, use the schema-property to add a JsonSchema for any configurations. When installing angular-cli-hooks, this schema is merged with the native Angular CLI builder schema.

Adding a JsonSchema makes both the hook configuration and the native builder configuration available when implementing the hook. Both are also listed when running ng build --help.

// index.ts in builder-hooks

import { BuilderOutput } from '@angular-devkit/architect';
import { hook } from 'angular-cli-hooks';
import { ESLint } from 'eslint';

export default [
  hook({
    name: 'build',
    schema: {
      properties: {
        failOnLintErrors: {
          type: 'boolean',
          description: 'Whether to fail the build on lint errors.',
        },
      },
    },
    before: async (
      { failOnLintErrors },
      { workspaceRoot }
    ): Promise<BuilderOutput> => {
      const eslint = new ESLint();
      const results = await eslint.lintFiles([`${workspaceRoot}/**/*.ts`]);

      if (results.length > 0) {
        console.log((await eslint.loadFormatter()).format(results));

        if (failOnLintErrors) {
          throw new Error('ESLint found lint errors.');
        }
      }

      return { success: true };
    },
  }),
];

This code hooks into ng build, but you can hook into other builders too.

Install the hook package wherever you want to hook into Angular CLI. Then add a angular-cli-hooks.json file to your project and specify the name of the package of hooks

{
  "$schema": "./node_modules/angular-cli-hooks/schema.json",
  "hookPackage": "builder-hooks"
}

or for multiple hook packages

{
  "$schema": "./node_modules/angular-cli-hooks/schema.json",
  "hookPackage": ["builder-hooks", "more-builder-hooks"]
}

Update angular.json to use angular-cli-hooks over @angular-devkit/build-angular.

{
  "architect": {
    "build": {
      "builder": "@angular-devkit/build-angular:browser"
    }
  }
}

becomes

{
  "architect": {
    "build": {
      "builder": "angular-cli-hooks:browser"
    }
  }
}

And that's it.

• The JsonSchema for custom configurations is merged with Angular native schemas in the postinstall hook of angular-cli-hooks. You have to reinstall to see changes.
• The before hook will only run before the Angular native builder is invoked the first time.
• The after hook will run after an Angular builder emits a BuilderOutput. This means the after hook will run for both fresh builds and rebuilds.