fix: threads multi-compiler

declarations/getESLint.d.ts

@@ -11,16 +11,25 @@
  */
 export function loadESLint(options: Options): Linter;
 /**
+ * @param {string|undefined} key
  * @param {number} poolSize
  * @param {Options} options
  * @returns {Linter}
  */
-export function loadESLintThreaded(poolSize: number, options: Options): Linter;
+export function loadESLintThreaded(
+  key: string | undefined,
+  poolSize: number,
+  options: Options
+): Linter;
 /**
+ * @param {string|undefined} key
  * @param {Options} options
  * @returns {Linter}
  */
-export default function getESLint({ threads, ...options }: Options): Linter;
+export default function getESLint(
+  key: string | undefined,
+  { threads, ...options }: Options
+): Linter;
 export type ESLint = import('eslint').ESLint;
 export type LintResult = import('eslint').ESLint.LintResult;
 export type Options = import('./options').PluginOptions &

declarations/index.d.ts

@@ -13,6 +13,7 @@ export class ESLintWebpackPlugin {
    * @returns {void}
    */
   apply(compiler: Compiler): void;
+  key: string | undefined;
   /**
    *
    * @param {Compiler} compiler

declarations/linter.d.ts

@@ -1,9 +1,11 @@
 /**
+ * @param {string|undefined} key
  * @param {Options} options
  * @param {Compilation} compilation
  * @returns {{lint: Linter, report: Reporter}}
  */
 export default function linter(
+  key: string | undefined,
   options: Options,
   compilation: Compilation
 ): {

src/getESLint.js

@@ -46,12 +46,13 @@ export function loadESLint(options) {
 }
 
 /**
+ * @param {string|undefined} key
  * @param {number} poolSize
  * @param {Options} options
  * @returns {Linter}
  */
-export function loadESLintThreaded(poolSize, options) {
-  const key = getCacheKey(options);
+export function loadESLintThreaded(key, poolSize, options) {
+  const cacheKey = getCacheKey(key, options);
   const { eslintPath = 'eslint' } = options;
   const source = require.resolve('./worker');
   const workerOptions = {
@@ -74,7 +75,7 @@ export function loadESLintThreaded(poolSize, options) {
       (worker && (await worker.lintFiles(files))) ||
       /* istanbul ignore next */ [],
     cleanup: async () => {
-      cache[key] = local;
+      cache[cacheKey] = local;
       context.lintFiles = (files) => local.lintFiles(files);
       if (worker) {
         worker.end();
@@ -87,10 +88,11 @@ export function loadESLintThreaded(poolSize, options) {
 }
 
 /**
+ * @param {string|undefined} key
  * @param {Options} options
  * @returns {Linter}
  */
-export default function getESLint({ threads, ...options }) {
+export default function getESLint(key, { threads, ...options }) {
   const max =
     typeof threads !== 'number'
       ? threads
@@ -99,18 +101,19 @@ export default function getESLint({ threads, ...options }) {
       : /* istanbul ignore next */
         threads;
 
-  const key = getCacheKey({ threads, ...options });
-  if (!cache[key]) {
-    cache[key] =
-      max > 1 ? loadESLintThreaded(max, options) : loadESLint(options);
+  const cacheKey = getCacheKey(key, { threads, ...options });
+  if (!cache[cacheKey]) {
+    cache[cacheKey] =
+      max > 1 ? loadESLintThreaded(key, max, options) : loadESLint(options);
   }
-  return cache[key];
+  return cache[cacheKey];
 }
 
 /**
+ * @param {string|undefined} key
  * @param {Options} options
  * @returns {string}
  */
-function getCacheKey(options) {
-  return JSON.stringify(options, jsonStringifyReplacerSortKeys);
+function getCacheKey(key, options) {
+  return JSON.stringify({ key, options }, jsonStringifyReplacerSortKeys);
 }

src/index.js

@@ -11,6 +11,7 @@ import { parseFiles, parseFoldersToGlobs } from './utils';
 /** @typedef {import('./options').Options} Options */
 
 const ESLINT_PLUGIN = 'ESLintWebpackPlugin';
+let counter = 0;
 
 export class ESLintWebpackPlugin {
   /**
@@ -26,6 +27,12 @@ export class ESLintWebpackPlugin {
    * @returns {void}
    */
   apply(compiler) {
+    // Generate key for each compilation,
+    // this differentiates one from the other when being cached.
+    this.key = compiler.name || `${ESLINT_PLUGIN}_${(counter += 1)}`;
+
+    // If `lintDirtyModulesOnly` is disabled,
+    // execute the linter on the build
     if (!this.options.lintDirtyModulesOnly) {
       compiler.hooks.run.tapPromise(ESLINT_PLUGIN, this.run);
     }
@@ -72,7 +79,7 @@ export class ESLintWebpackPlugin {
       let report;
 
       try {
-        ({ lint, report } = linter(options, compilation));
+        ({ lint, report } = linter(this.key, options, compilation));
       } catch (e) {
         compilation.errors.push(e);
         return;

src/linter.js

@@ -21,11 +21,12 @@ import getESLint from './getESLint';
 const resultStorage = new WeakMap();
 
 /**
+ * @param {string|undefined} key
  * @param {Options} options
  * @param {Compilation} compilation
  * @returns {{lint: Linter, report: Reporter}}
  */
-export default function linter(options, compilation) {
+export default function linter(key, options, compilation) {
   /** @type {ESLint} */
   let eslint;
 
@@ -41,7 +42,7 @@ export default function linter(options, compilation) {
   const crossRunResultStorage = getResultStorage(compilation);
 
   try {
-    ({ eslint, lintFiles, cleanup } = getESLint(options));
+    ({ eslint, lintFiles, cleanup } = getESLint(key, options));
   } catch (e) {
     throw new ESLintError(e.message);
   }

test/threads.test.js

@@ -6,7 +6,7 @@ import { loadESLint, loadESLintThreaded } from '../src/getESLint';
 describe('Threading', () => {
   test('Threaded interface should look like non-threaded interface', async () => {
     const single = loadESLint({});
-    const threaded = loadESLintThreaded(1, {});
+    const threaded = loadESLintThreaded('foo', 1, {});
     for (const key of Object.keys(single)) {
       expect(typeof single[key]).toEqual(typeof threaded[key]);
     }
@@ -21,7 +21,7 @@ describe('Threading', () => {
   });
 
   test('Threaded should lint files', async () => {
-    const threaded = loadESLintThreaded(1, { ignore: false });
+    const threaded = loadESLintThreaded('bar', 1, { ignore: false });
     try {
       const [good, bad] = await Promise.all([
         threaded.lintFiles(join(__dirname, 'fixtures/good.js')),