feat: make knip understand yarn pnp

packages/knip/fixtures/yarn-pnp/.yarnrc.yml

@@ -0,0 +1 @@
+enableGlobalCache: false

packages/knip/fixtures/yarn-pnp/index.js

@@ -0,0 +1,3 @@
+import { dep } from '@sample-package/dep'
+
+dep;

packages/knip/fixtures/yarn-pnp/knip.json

@@ -0,0 +1,3 @@
+{
+  "ignore": ["**/.pnp.{cjs,mjs,js}", "**/.pnp.loader.{cjs,mjs,js}", "**/sample-packages/**"]
+}

packages/knip/fixtures/yarn-pnp/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "@fixtures/yarn-pnp-test",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "packageManager": "[email protected]",
+  "dependencies": {
+    "@sample-package/dep": "./sample-packages/dep",
+    "@sample-package/peer": "./sample-packages/peer"
+  }
+}

packages/knip/fixtures/yarn-pnp/sample-packages/dep/index.js

@@ -0,0 +1 @@
+export const dep = 'dep';

packages/knip/fixtures/yarn-pnp/sample-packages/dep/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@sample-package/dep",
+  "version": "0.0.0",
+  "main": "./index.js",
+  "peerDependencies": {
+    "@sample-package/peer": "*"
+  }
+}

packages/knip/fixtures/yarn-pnp/sample-packages/peer/index.js

@@ -0,0 +1 @@
+export const peer = 'peer';

packages/knip/fixtures/yarn-pnp/sample-packages/peer/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "@sample-package/peer",
+  "version": "0.0.0",
+  "main": "./index.js"
+}

packages/knip/fixtures/yarn-pnp/yarn.lock

@@ -0,0 +1,31 @@
+# This file is generated by running "yarn install" inside your project.
+# Manual changes might be lost - proceed with caution!
+
+__metadata:
+  version: 8
+  cacheKey: 10c0
+
+"@fixtures/yarn-pnp-test@workspace:.":
+  version: 0.0.0-use.local
+  resolution: "@fixtures/yarn-pnp-test@workspace:."
+  dependencies:
+    "@sample-package/dep": ./sample-packages/dep
+    "@sample-package/peer": ./sample-packages/peer
+  languageName: unknown
+  linkType: soft
+
+"@sample-package/dep@file:./sample-packages/dep::locator=%40fixtures%2Fyarn-pnp-test%40workspace%3A.":
+  version: 0.0.0
+  resolution: "@sample-package/dep@file:./sample-packages/dep#./sample-packages/dep::hash=537a59&locator=%40fixtures%2Fyarn-pnp-test%40workspace%3A."
+  peerDependencies:
+    "@sample-package/peer": "*"
+  checksum: 10c0/e8bd21d44ae40880d3512bc09edededd1a98716da88727fba4983465d9b452bfebc48257239632ed41d34d75d5fed03183d7422c352e90554e95ebee82c2f83b
+  languageName: node
+  linkType: hard
+
+"@sample-package/peer@file:./sample-packages/peer::locator=%40fixtures%2Fyarn-pnp-test%40workspace%3A.":
+  version: 0.0.0
+  resolution: "@sample-package/peer@file:./sample-packages/peer#./sample-packages/peer::hash=3bb161&locator=%40fixtures%2Fyarn-pnp-test%40workspace%3A."
+  checksum: 10c0/ec625a2dd9ddeeccfb18550e0789ddb92c6b65d7e94514f3eb62a222b500297dc2d50aadc748d5e3067374bdf74e634dfa36cec258e334ca5ea19565f85b44e6
+  languageName: node
+  linkType: hard

packages/knip/src/manifest/helpers.ts

@@ -1,12 +1,82 @@
 import type { Scripts } from '../types/package-json.js';
-import { join } from '../util/path.js';
+import { isFile } from '../util/fs.js';
+import { dirname, join } from '../util/path.js';
 import { _require } from '../util/require.js';
 
+let isPnPEnabled: boolean | 'NOT_DETERMINED_YET' = 'NOT_DETERMINED_YET';
+
 type LoadPackageManifestOptions = { dir: string; packageName: string; cwd: string };
 
+const findNearestPnPFile = (startDir: string): string | null => {
+  // Find the nearest .pnp.cjs file by traversing up
+  let currentDir = startDir;
+  while (currentDir !== '/') {
+    const pnpPath = join(currentDir, '.pnp.cjs');
+    if (isFile(pnpPath)) {
+      return pnpPath;
+    }
+    // Move up one directory
+    const parentDir = dirname(currentDir);
+    if (parentDir === currentDir) {
+      break; // Reached root
+    }
+    currentDir = parentDir;
+  }
+  return null;
+};
+
+const tryLoadManifestWithYarnPnp = (cwd: string, packageName: string) => {
+  if (isPnPEnabled === false) {
+    return null;
+  }
+
+  try {
+    if (isPnPEnabled === 'NOT_DETERMINED_YET') {
+      const pnpPath = findNearestPnPFile(cwd);
+
+      if (pnpPath != null) {
+        const pnp = _require(pnpPath);
+        pnp.setup();
+        isPnPEnabled = true;
+      } else {
+        isPnPEnabled = false;
+      }
+    }
+
+    if (isPnPEnabled) {
+      const pnpApi = _require('pnpapi');
+
+      if (pnpApi != null) {
+        const resolvedPath = pnpApi.resolveRequest(packageName, cwd);
+
+        if (resolvedPath) {
+          const packageLocation = pnpApi.findPackageLocator(resolvedPath);
+          const packageInformation = pnpApi.getPackageInformation(packageLocation);
+          const packageJsonPath = join(packageInformation.packageLocation, 'package.json');
+
+          // We need to require fs dynamically here because pnp patches it.
+          const _readFileSync = _require('fs').readFileSync;
+          const manifest = JSON.parse(_readFileSync(packageJsonPath, 'utf8'));
+
+          return manifest;
+        }
+      }
+    }
+  } catch (_error) {
+    // Explicitly suppressing errors here
+  }
+
+  return null;
+};
+
 export const loadPackageManifest = ({ dir, packageName, cwd }: LoadPackageManifestOptions) => {
-  // TODO Not sure what's the most efficient way to get a package.json, but this seems to do the job across package
-  // managers (npm, Yarn, pnpm)
+  // 1. Try Yarn PnP first
+  const pnpManifest = tryLoadManifestWithYarnPnp(cwd, packageName);
+  if (pnpManifest != null) {
+    return pnpManifest;
+  }
+
+  // 2. Fallback to traditional node_modules resolution
   try {
     return _require(join(dir, 'node_modules', packageName, 'package.json'));
   } catch (_error) {

packages/knip/test/yarn-pnp.test.ts

@@ -0,0 +1,22 @@
+import { test } from 'bun:test';
+import assert from 'node:assert/strict';
+import { main } from '../src/index.js';
+import { resolve } from '../src/util/path.js';
+import baseArguments from './helpers/baseArguments.js';
+import baseCounters from './helpers/baseCounters.js';
+
+const cwd = resolve('fixtures/yarn-pnp');
+
+test('Find unused dependencies', async () => {
+  const { counters } = await main({
+    ...baseArguments,
+    cwd,
+    isStrict: true,
+  });
+
+  assert.deepEqual(counters, {
+    ...baseCounters,
+    processed: 1,
+    total: 4,
+  });
+});