cat-knip

Find NestJS providers exported by a module but never injected by another module.

Install

pnpm add -D cat-knip

Use

import {
  expectNoUnusedExports,
  getModuleRefWithSnapshot,
} from 'cat-knip/testing';
import { AppModule } from '../src/app.module';

it('has no unused module exports', async () => {
  await using moduleRef = await getModuleRefWithSnapshot({
    imports: [AppModule],
  });

  expectNoUnusedExports(moduleRef);
});

getModuleRefWithSnapshot compiles with snapshot: true and closes the module when the await using scope exits. await using requires TypeScript 5.2 or newer.

When the assertion fails, it prints one unused export per line without internal graph node IDs:

cat-knip found 2 unused module exports:

- AuthModule => AUTH_CLIENT
- SharedModule => SharedService

When creating a testing module directly, snapshot: true must be passed to compile().

Ignoring exports

Use the ignore option with getUnusedExports, expectNoUnusedExports, or analyzeModule to exclude exports that cat-knip should not report:

getUnusedExports(moduleRef, {
  ignore: {
    modules: ['ThirdPartyModule'],
    tokens: ['SharedService'],
    exactMatches: ['AuthModule:AUTH_CLIENT'],
  },
});

• modules ignores every export owned by a named module. Use it when an entire dependency module is outside your control.
• tokens ignores a token regardless of which module owns it. Use it for an intentional public token that may be exported by multiple modules.
• exactMatches ignores only a specific ModuleName:token pair. Use it when a dependency module has particular exports you do not own, without suppressing its other findings.

For example, Nest dependencies can add exported providers to the runtime graph. Ignore those dependency-owned exports while continuing to check first-party exports:

expectNoUnusedExports(moduleRef, {
  ignore: {
    modules: ['ClsCommonModule', 'ClsRootModule', 'WinstonModule'],
    exactMatches: ['ConfigModule:CONFIGURATION(app)'],
  },
});

Requires Node.js 20.5 or newer and NestJS 10 or 11. cat-knip analyzes the runtime DI graph; it has no CLI and does not parse source files.

Contributions are welcome; see CONTRIBUTING.md.

Why "cat-knip"?

NestJS's logo is a cat, and there's a unused code detection tool called "knip". The #dad-joke was right there, I couldn't help myself.