Custom Builder

Wrapping the v3 Angular builder's runBuilder factory to preprocess its options — and what it cannot do.

The adapter's builder factory is exported as runBuilder, so you can wrap it in your own Architect builder and adjust the options before delegating. That is useful for computing an option per environment, deriving an output path, or applying a workspace-wide default without repeating it in angular.json.

The Pattern

1. Write a builder file that calls runBuilder with a modified options object.
2. Point the relevant angular.json targets at your wrapper instead of @angular-architects/native-federation:build.

1. The wrapper

The v3 package has no exports map and its main is src/index.js, so the builder module is reachable by its path inside the package:

// custom-builder.js
const { runBuilder } = require('@angular-architects/native-federation/src/builders/build/builder');
const { createBuilder } = require('@angular-devkit/architect');

async function* customBuilder(options, context) {
  const nfOptions = {
    ...options,
    outputPath: options.outputPath ?? `dist/${context.target.project}`,
    rebuildDelay: process.env.CI ? 0 : options.rebuildDelay,
  };

  yield* runBuilder(nfOptions, context);
}

module.exports = createBuilder(customBuilder);

runBuilder is an async generator yielding BuilderOutput values, so yield* forwards them unchanged — the dev-server and watch behaviour keep working.

2. Wire it in angular.json

{
  "projects": {
    "mfe1": {
      "architect": {
        "build": {
          "builder": "./custom-builder",
          "options": {},
          "configurations": {
            "production": { "target": "mfe1:esbuild:production" },
            "development": { "target": "mfe1:esbuild:development", "dev": true }
          },
          "defaultConfiguration": "production"
        },
        "serve": {
          "builder": "./custom-builder",
          "options": {
            "target": "mfe1:serve-original:development",
            "dev": true
          }
        }
      }
    }
  }
}

You are swapping the builder, not the options schema — every option from Builder → Options still applies, and your wrapper receives them as its first argument.

Notes

• runBuilder lives at an internal path. It is not part of the public API guarantee — a minor bump may move or rename it. Pin the adapter version when you ship a custom builder.
• Your wrapper runs in the Architect process, so it can read the environment and the workspace, but it cannot reach into the federation build itself.
• If you need to change what gets bundled rather than how the builder is invoked, that belongs in federation.config.js — see Angular Config.

Related

• Builder — the options the wrapper inherits.
• Core → Build Adapters — the BuildAdapter contract, if you would rather drive the core build yourself with a different bundler.