Integration with Vitest (Vite)

Vitest — and any Vite-based pipeline — compiles TypeScript with esbuild, which does not run tsconfig plugins transformers. Forger ships a Vite plugin that applies the same compile-time transformer in these pipelines.

How it works

defineForgerVitestPlugin() compiles the project once with the TypeScript compiler, caches the program, and rewrites every Forger.create<T>()/Forger.createWith<T>() call exactly like the ts-jest and Angular (webpack) integrations do.

1. Install dependencies

npm install --save-dev @artstesh/forger vitest

No ts-patch is needed on this route — the plugin drives the TypeScript compiler directly.

2. Register the plugin

/** vitest.config.ts */
import { defineConfig } from 'vitest/config';
import { defineForgerVitestPlugin } from '@artstesh/forger/vitest';

export default defineConfig({
  plugins: [defineForgerVitestPlugin({ tsconfig: 'tsconfig.spec.json' })],
});

The plugin is published on the dedicated @artstesh/forger/vitest subpath, not on the package root: it loads Node-only modules (path, the TypeScript compiler) at import time, and the root entry has to stay browser-safe so Karma/webpack browser bundles that merely include Forger keep working.

The plugin runs as a pre transform: every .ts file with Forger.create/Forger.createWith calls is rewritten before esbuild transpiles it.

3. Point the plugin at the right tsconfig

tsconfig must cover every file that calls Forger — the type checker can only resolve types of files the compiler program owns. For an Angular workspace that is usually tsconfig.spec.json; files missing from the config are added on first sight, but a complete include list is faster.

Angular on esbuild builders

The esbuild-based Angular builders (@angular/build:karma, @angular/build:unit-test, @angular/build:application) do not run custom TypeScript transformers and offer no hook for them — the webpack patch from Integration with Angular does not apply there. The supported route for specs on these builders is a standalone Vitest setup with this plugin, as described above.

Notes

The rewritten code is returned without a source map: stack traces of rewritten lines may be slightly offset.
If a call reaches runtime unrewritten anyway, Forger.create<T>() throws a descriptive error (see Caveats) — it no longer fails silently.

14 September 2026