Expose @babel/eslint-parser/experimental-worker (#13398)

* Expose `@babel/eslint-parser/experimental-worker`

* Fix `@babel/runtime` build on Windows

eslint/babel-eslint-parser/package.json

@@ -23,6 +23,7 @@
   "type": "commonjs",
   "exports": {
     ".": "./lib/index.cjs",
+    "./experimental-worker": "./lib/experimental-worker.cjs",
     "./package.json": "./package.json"
   },
   "peerDependencies": {

eslint/babel-eslint-parser/src/analyze-scope.cjs

@@ -4,13 +4,11 @@ const OriginalPatternVisitor = require("eslint-scope/lib/pattern-visitor");
 const OriginalReferencer = require("eslint-scope/lib/referencer");
 const { getKeys: fallback } = require("eslint-visitor-keys");
 
-const { getTypesInfo, getVisitorKeys } = require("./client.cjs");
-
 let visitorKeysMap;
-function getVisitorValues(nodeType) {
+function getVisitorValues(nodeType, client) {
   if (visitorKeysMap) return visitorKeysMap[nodeType];
 
-  const { FLOW_FLIPPED_ALIAS_KEYS, VISITOR_KEYS } = getTypesInfo();
+  const { FLOW_FLIPPED_ALIAS_KEYS, VISITOR_KEYS } = client.getTypesInfo();
 
   const flowFlippedAliasKeys = FLOW_FLIPPED_ALIAS_KEYS.concat([
     "ArrayPattern",
@@ -63,6 +61,13 @@ class PatternVisitor extends OriginalPatternVisitor {
 }
 
 class Referencer extends OriginalReferencer {
+  #client;
+
+  constructor(options, scopeManager, client) {
+    super(options, scopeManager);
+    this.#client = client;
+  }
+
   // inherits.
   visitPattern(node, options, callback) {
     if (!node) {
@@ -264,7 +269,7 @@ class Referencer extends OriginalReferencer {
     }
 
     // get property to check (params, id, etc...)
-    const visitorValues = getVisitorValues(node.type);
+    const visitorValues = getVisitorValues(node.type, this.#client);
     if (!visitorValues) {
       return;
     }
@@ -328,7 +333,7 @@ class Referencer extends OriginalReferencer {
   }
 }
 
-module.exports = function analyzeScope(ast, parserOptions) {
+module.exports = function analyzeScope(ast, parserOptions, client) {
   const options = {
     ignoreEval: true,
     optimistic: false,
@@ -343,10 +348,10 @@ module.exports = function analyzeScope(ast, parserOptions) {
     fallback,
   };
 
-  options.childVisitorKeys = getVisitorKeys();
+  options.childVisitorKeys = client.getVisitorKeys();
 
   const scopeManager = new escope.ScopeManager(options);
-  const referencer = new Referencer(options, scopeManager);
+  const referencer = new Referencer(options, scopeManager, client);
 
   referencer.visit(ast);
 

eslint/babel-eslint-parser/src/client.cjs

@@ -1,67 +1,105 @@
 const path = require("path");
 
-let send;
+const ACTIONS = {
+  GET_VERSION: "GET_VERSION",
+  GET_TYPES_INFO: "GET_TYPES_INFO",
+  GET_VISITOR_KEYS: "GET_VISITOR_KEYS",
+  GET_TOKEN_LABELS: "GET_TOKEN_LABELS",
+  MAYBE_PARSE: "MAYBE_PARSE",
+  MAYBE_PARSE_SYNC: "MAYBE_PARSE_SYNC",
+};
 
-exports.getVersion = sendCached("GET_VERSION");
+class Client {
+  #send;
 
-exports.getTypesInfo = sendCached("GET_TYPES_INFO");
+  constructor(send) {
+    this.#send = send;
+  }
 
-exports.getVisitorKeys = sendCached("GET_VISITOR_KEYS");
+  #vCache;
+  getVersion() {
+    return (this.#vCache ??= this.#send(ACTIONS.GET_VERSION, undefined));
+  }
 
-exports.getTokLabels = sendCached("GET_TOKEN_LABELS");
+  #tiCache;
+  getTypesInfo() {
+    return (this.#tiCache ??= this.#send(ACTIONS.GET_TYPES_INFO, undefined));
+  }
 
-exports.maybeParse = (code, options) => send("MAYBE_PARSE", { code, options });
+  #vkCache;
+  getVisitorKeys() {
+    return (this.#vkCache ??= this.#send(ACTIONS.GET_VISITOR_KEYS, undefined));
+  }
 
-function sendCached(action) {
-  let cache = null;
+  #tlCache;
+  getTokLabels() {
+    return (this.#tlCache ??= this.#send(ACTIONS.GET_TOKEN_LABELS, undefined));
+  }
 
-  return () => {
-    if (!cache) cache = send(action, undefined);
-    return cache;
-  };
+  maybeParse(code, options) {
+    return this.#send(ACTIONS.MAYBE_PARSE, { code, options });
+  }
 }
 
-if (process.env.BABEL_8_BREAKING) {
-  const {
-    Worker,
-    receiveMessageOnPort,
-    MessageChannel,
-    SHARE_ENV,
-  } = require("worker_threads");
+// We need to run Babel in a worker for two reasons:
+// 1. ESLint workers must be CJS files, and this is a problem
+//    since Babel 8+ uses native ESM
+// 2. ESLint parsers must run synchronously, but many steps
+//    of Babel's config loading (which is done for each file)
+//    can be asynchronous
+// If ESLint starts supporting async parsers, we can move
+// everything back to the main thread.
+exports.WorkerClient = class WorkerClient extends Client {
+  static #worker_threads_cache;
+  static get #worker_threads() {
+    return (WorkerClient.#worker_threads_cache ??= require("worker_threads"));
+  }
 
-  // We need to run Babel in a worker for two reasons:
-  // 1. ESLint workers must be CJS files, and this is a problem
-  //    since Babel 8+ uses native ESM
-  // 2. ESLint parsers must run synchronously, but many steps
-  //    of Babel's config loading (which is done for each file)
-  //    can be asynchronous
-  // If ESLint starts supporting async parsers, we can move
-  // everything back to the main thread.
-  const worker = new Worker(
+  #worker = new WorkerClient.#worker_threads.Worker(
     path.resolve(__dirname, "../lib/worker/index.cjs"),
-    { env: SHARE_ENV },
+    { env: WorkerClient.#worker_threads.SHARE_ENV },
   );
 
-  // The worker will never exit by itself. Prevent it from keeping
-  // the main process alive.
-  worker.unref();
+  #signal = new Int32Array(new SharedArrayBuffer(4));
 
-  const signal = new Int32Array(new SharedArrayBuffer(4));
+  constructor() {
+    super((action, payload) => {
+      this.#signal[0] = 0;
+      const subChannel = new WorkerClient.#worker_threads.MessageChannel();
 
-  send = (action, payload) => {
-    signal[0] = 0;
-    const subChannel = new MessageChannel();
+      this.#worker.postMessage(
+        { signal: this.#signal, port: subChannel.port1, action, payload },
+        [subChannel.port1],
+      );
 
-    worker.postMessage({ signal, port: subChannel.port1, action, payload }, [
-      subChannel.port1,
-    ]);
-
-    Atomics.wait(signal, 0, 0);
-    const { message } = receiveMessageOnPort(subChannel.port2);
+      Atomics.wait(this.#signal, 0, 0);
+      const { message } = WorkerClient.#worker_threads.receiveMessageOnPort(
+        subChannel.port2,
+      );
 
       if (message.error) throw Object.assign(message.error, message.errorData);
       else return message.result;
+    });
+
+    // The worker will never exit by itself. Prevent it from keeping
+    // the main process alive.
+    this.#worker.unref();
+  }
+};
+
+if (!process.env.BABEL_8_BREAKING) {
+  exports.LocalClient = class LocalClient extends Client {
+    static #handleMessage;
+
+    constructor() {
+      LocalClient.#handleMessage ??= require("./worker/handle-message.cjs");
+
+      super((action, payload) => {
+        return LocalClient.#handleMessage(
+          action === ACTIONS.MAYBE_PARSE ? ACTIONS.MAYBE_PARSE_SYNC : action,
+          payload,
+        );
+      });
+    }
   };
-} else {
-  send = require("./worker/index.cjs");
 }

eslint/babel-eslint-parser/src/experimental-worker.cjs

@@ -0,0 +1,22 @@
+const [major, minor] = process.versions.node.split(".").map(Number);
+
+if (major < 12 || (major === 12 && minor < 3)) {
+  throw new Error(
+    "@babel/eslint-parser/experimental-worker requires Node.js >= 12.3.0",
+  );
+}
+
+const { normalizeESLintConfig } = require("./configuration.cjs");
+const analyzeScope = require("./analyze-scope.cjs");
+const baseParse = require("./parse.cjs");
+
+const { WorkerClient } = require("./client.cjs");
+const client = new WorkerClient();
+
+exports.parseForESLint = function (code, options = {}) {
+  const normalizedOptions = normalizeESLintConfig(options);
+  const ast = baseParse(code, normalizedOptions, client);
+  const scopeManager = analyzeScope(ast, normalizedOptions, client);
+
+  return { ast, scopeManager, visitorKeys: client.getVisitorKeys() };
+};

eslint/babel-eslint-parser/src/index.cjs

@@ -1,63 +1,20 @@
-const semver = require("semver");
 const { normalizeESLintConfig } = require("./configuration.cjs");
 const analyzeScope = require("./analyze-scope.cjs");
-const {
-  getVersion,
-  getVisitorKeys,
-  getTokLabels,
-  maybeParse,
-} = require("./client.cjs");
-const convert = require("./convert/index.cjs");
+const baseParse = require("./parse.cjs");
 
-const babelParser = require(require.resolve("@babel/parser", {
-  paths: [require.resolve("@babel/core/package.json")],
-}));
-
-let isRunningMinSupportedCoreVersion = null;
-
-function baseParse(code, options) {
-  // Ensure we're using a version of `@babel/core` that includes `parse()` and `tokTypes`.
-  const minSupportedCoreVersion = ">=7.2.0";
-
-  if (typeof isRunningMinSupportedCoreVersion !== "boolean") {
-    isRunningMinSupportedCoreVersion = semver.satisfies(
-      getVersion(),
-      minSupportedCoreVersion,
-    );
-  }
-
-  if (!isRunningMinSupportedCoreVersion) {
-    throw new Error(
-      `@babel/eslint-parser@${
-        PACKAGE_JSON.version
-      } does not support @babel/core@${getVersion()}. Please upgrade to @babel/core@${minSupportedCoreVersion}.`,
-    );
-  }
-
-  const { ast, parserOptions } = maybeParse(code, options);
-
-  if (ast) return ast;
-
-  try {
-    return convert.ast(
-      babelParser.parse(code, parserOptions),
-      code,
-      getTokLabels(),
-      getVisitorKeys(),
-    );
-  } catch (err) {
-    throw convert.error(err);
-  }
-}
+const { LocalClient, WorkerClient } = require("./client.cjs");
+const client = new (
+  process.env.BABEL_8_BREAKING ? WorkerClient : LocalClient
+)();
 
 exports.parse = function (code, options = {}) {
-  return baseParse(code, normalizeESLintConfig(options));
+  return baseParse(code, normalizeESLintConfig(options), client);
 };
 
 exports.parseForESLint = function (code, options = {}) {
   const normalizedOptions = normalizeESLintConfig(options);
-  const ast = baseParse(code, normalizedOptions);
-  const scopeManager = analyzeScope(ast, normalizedOptions);
+  const ast = baseParse(code, normalizedOptions, client);
+  const scopeManager = analyzeScope(ast, normalizedOptions, client);
 
-  return { ast, scopeManager, visitorKeys: getVisitorKeys() };
+  return { ast, scopeManager, visitorKeys: client.getVisitorKeys() };
 };

eslint/babel-eslint-parser/src/parse.cjs

@@ -0,0 +1,45 @@
+"use strict";
+
+const semver = require("semver");
+const convert = require("./convert/index.cjs");
+
+const babelParser = require(require.resolve("@babel/parser", {
+  paths: [require.resolve("@babel/core/package.json")],
+}));
+
+let isRunningMinSupportedCoreVersion = null;
+
+module.exports = function parse(code, options, client) {
+  // Ensure we're using a version of `@babel/core` that includes `parse()` and `tokTypes`.
+  const minSupportedCoreVersion = ">=7.2.0";
+
+  if (typeof isRunningMinSupportedCoreVersion !== "boolean") {
+    isRunningMinSupportedCoreVersion = semver.satisfies(
+      client.getVersion(),
+      minSupportedCoreVersion,
+    );
+  }
+
+  if (!isRunningMinSupportedCoreVersion) {
+    throw new Error(
+      `@babel/eslint-parser@${
+        PACKAGE_JSON.version
+      } does not support @babel/core@${client.getVersion()}. Please upgrade to @babel/core@${minSupportedCoreVersion}.`,
+    );
+  }
+
+  const { ast, parserOptions } = client.maybeParse(code, options);
+
+  if (ast) return ast;
+
+  try {
+    return convert.ast(
+      babelParser.parse(code, parserOptions),
+      code,
+      client.getTokLabels(),
+      client.getVisitorKeys(),
+    );
+  } catch (err) {
+    throw convert.error(err);
+  }
+};

eslint/babel-eslint-parser/src/worker/configuration.cjs

@@ -41,7 +41,7 @@ function normalizeParserOptions(options) {
   };
 }
 
-function validateResolvedConfig(config, options) {
+function validateResolvedConfig(config, options, parseOptions) {
   if (config !== null) {
     if (options.requireConfigFile !== false) {
       if (!config.hasFilesystemConfig()) {
@@ -54,8 +54,10 @@ function validateResolvedConfig(config, options) {
         throw new Error(error);
       }
     }
-    return config.options;
+    if (config.options) return config.options;
   }
+
+  return getDefaultParserOptions(parseOptions);
 }
 
 function getDefaultParserOptions(options) {
@@ -70,25 +72,14 @@ function getDefaultParserOptions(options) {
   };
 }
 
-module.exports = function normalizeBabelParseConfig(options) {
+exports.normalizeBabelParseConfig = async function (options) {
   const parseOptions = normalizeParserOptions(options);
-
-  if (process.env.BABEL_8_BREAKING) {
-    return babel
-      .loadPartialConfigAsync(parseOptions)
-      .then(config => validateConfigWithFallback(config));
-  } else {
-    const config = babel.loadPartialConfigSync(parseOptions);
-    return validateConfigWithFallback(config);
-  }
-
-  function validateConfigWithFallback(inputConfig) {
-    const result = validateResolvedConfig(inputConfig, options);
-    if (result) {
-      return result;
-    } else {
-      // Fallback when `loadPartialConfig` returns `null` (e.g.: when the file is ignored)
-      return getDefaultParserOptions(parseOptions);
-    }
-  }
+  const config = await babel.loadPartialConfigAsync(parseOptions);
+  return validateResolvedConfig(config, options, parseOptions);
+};
+
+exports.normalizeBabelParseConfigSync = function (options) {
+  const parseOptions = normalizeParserOptions(options);
+  const config = babel.loadPartialConfigSync(parseOptions);
+  return validateResolvedConfig(config, options, parseOptions);
 };

eslint/babel-eslint-parser/src/worker/handle-message.cjs

@@ -0,0 +1,36 @@
+const babel = require("./babel-core.cjs");
+const maybeParse = require("./maybeParse.cjs");
+const { getVisitorKeys, getTokLabels } = require("./ast-info.cjs");
+const {
+  normalizeBabelParseConfig,
+  normalizeBabelParseConfigSync,
+} = require("./configuration.cjs");
+
+module.exports = function handleMessage(action, payload) {
+  switch (action) {
+    case "GET_VERSION":
+      return babel.version;
+    case "GET_TYPES_INFO":
+      return {
+        FLOW_FLIPPED_ALIAS_KEYS: babel.types.FLIPPED_ALIAS_KEYS.Flow,
+        VISITOR_KEYS: babel.types.VISITOR_KEYS,
+      };
+    case "GET_TOKEN_LABELS":
+      return getTokLabels();
+    case "GET_VISITOR_KEYS":
+      return getVisitorKeys();
+    case "MAYBE_PARSE":
+      return normalizeBabelParseConfig(payload.options).then(options =>
+        maybeParse(payload.code, options),
+      );
+    case "MAYBE_PARSE_SYNC":
+      if (!process.env.BABEL_8_BREAKING) {
+        return maybeParse(
+          payload.code,
+          normalizeBabelParseConfigSync(payload.options),
+        );
+      }
+  }
+
+  throw new Error(`Unknown internal parser worker action: ${action}`);
+};

eslint/babel-eslint-parser/src/worker/index.cjs

@@ -1,43 +1,9 @@
 const babel = require("./babel-core.cjs");
-const maybeParse = require("./maybeParse.cjs");
-const { getVisitorKeys, getTokLabels } = require("./ast-info.cjs");
-const normalizeBabelParseConfig = require("./configuration.cjs");
+const handleMessage = require("./handle-message.cjs");
 
-function handleMessage(action, payload) {
-  switch (action) {
-    case "GET_VERSION":
-      return babel.version;
-    case "GET_TYPES_INFO":
-      return {
-        FLOW_FLIPPED_ALIAS_KEYS: babel.types.FLIPPED_ALIAS_KEYS.Flow,
-        VISITOR_KEYS: babel.types.VISITOR_KEYS,
-      };
-    case "GET_TOKEN_LABELS":
-      return getTokLabels();
-    case "GET_VISITOR_KEYS":
-      return getVisitorKeys();
-    case "MAYBE_PARSE":
-      if (process.env.BABEL_8_BREAKING) {
-        return normalizeBabelParseConfig(payload.options).then(options =>
-          maybeParse(payload.code, options),
-        );
-      } else {
-        return maybeParse(
-          payload.code,
-          normalizeBabelParseConfig(payload.options),
-        );
-      }
-  }
+const { parentPort } = require("worker_threads");
 
-  throw new Error(`Unknown internal parser worker action: ${action}`);
-}
-
-if (process.env.BABEL_8_BREAKING) {
-  const { parentPort } = require("worker_threads");
-
-  parentPort.addListener(
-    "message",
-    async ({ signal, port, action, payload }) => {
+parentPort.addListener("message", async ({ signal, port, action, payload }) => {
   let response;
 
   try {
@@ -59,8 +25,4 @@ if (process.env.BABEL_8_BREAKING) {
     Atomics.store(signal, 0, 1);
     Atomics.notify(signal, 0);
   }
-    },
-  );
-} else {
-  module.exports = handleMessage;
-}
+});

eslint/babel-eslint-tests/test/fixtures/mjs-config-file-babel-7/.eslintrc.js

@@ -0,0 +1,13 @@
+module.exports = {
+  root: true,
+  parser: "@babel/eslint-parser/experimental-worker",
+  parserOptions: {
+    babelOptions: {
+      configFile: __dirname + "/babel.config.mjs",
+      sourceType: "module",
+    },
+  },
+  rules: {
+    "template-curly-spacing": "error",
+  },
+};

eslint/babel-eslint-tests/test/fixtures/mjs-config-file-babel-7/a.js

@@ -0,0 +1 @@
+export default () => <div />;

eslint/babel-eslint-tests/test/fixtures/mjs-config-file-babel-7/babel.config.mjs

@@ -0,0 +1,3 @@
+export default {
+  presets: ["@babel/preset-react"],
+};

eslint/babel-eslint-tests/test/fixtures/mjs-config-file/.eslintrc.js

@@ -1,6 +1,6 @@
 module.exports = {
   root: true,
-  parser: "@babel/eslint-parser",
+  parser: "@babel/eslint-parser/experimental-worker",
   parserOptions: {
     babelOptions: {
       configFile: __dirname + "/babel.config.mjs",

eslint/babel-eslint-tests/test/integration/config-files.js

@@ -16,4 +16,21 @@ describe("Babel config files", () => {
       ]),
     ).toMatchObject({ errorCount: 0 });
   });
+
+  const babel7node12 =
+    process.env.BABEL_8_BREAKING || parseInt(process.versions.node) < 12
+      ? it.skip
+      : it;
+
+  babel7node12("experimental worker works with babel.config.mjs", () => {
+    const engine = new eslint.CLIEngine({ ignore: false });
+    expect(
+      engine.executeOnFiles([
+        path.resolve(
+          path.dirname(fileURLToPath(import.meta.url)),
+          `../fixtures/mjs-config-file-babel-7/a.js`,
+        ),
+      ]),
+    ).toMatchObject({ errorCount: 0 });
+  });
 });

jest.config.js

@@ -1,3 +1,5 @@
+const supportsESM = parseInt(process.versions.node) >= 12;
+
 module.exports = {
   collectCoverageFrom: [
     "packages/*/src/**/*.{js,mjs,ts}",
@@ -40,6 +42,7 @@ module.exports = {
     "/test/__data__/",
     "<rootDir>/build/",
   ],
+  resolver: supportsESM ? "./test/jestExportsMapResolver.cjs" : null,
   // We don't need module name mappers here as depedencies of workspace
   // package should be declared explicitly in the package.json
   // Yarn will generate correct file links so that Jest can resolve correctly

package.json

@@ -43,6 +43,7 @@
     "babel-plugin-transform-charcodes": "^0.2.0",
     "chalk": "^2.4.2",
     "charcodes": "^0.2.0",
+    "enhanced-resolve": "^5.8.2",
     "eslint": "^7.27.0",
     "eslint-import-resolver-node": "^0.3.4",
     "eslint-plugin-flowtype": "^5.7.2",

packages/babel-plugin-transform-runtime/scripts/build-dist.js

@@ -127,7 +127,7 @@ function writeHelperFile(
     buildHelper(runtimeName, pkgDirname, fullPath, helperName, { esm, corejs })
   );
 
-  return `./${filePath}`;
+  return esm ? `./helpers/esm/${fileName}` : `./helpers/${fileName}`;
 }
 
 function writeHelpers(runtimeName, { corejs } = {}) {
@@ -164,12 +164,13 @@ function writeHelpers(runtimeName, { corejs } = {}) {
     // - Node.js <13.2.0 will fail resolving the first array entry, and will
     //   fallback to the second entry (the CJS file)
     // In Babel 8 we can simplify this.
-    helperSubExports[`./${helperPath}`] = [
+    helperSubExports[`./${path.posix.join("helpers", helperName)}`] = [
       { node: cjs, import: esm, default: cjs },
       cjs,
     ];
     // For backward compatibility. We can remove this in Babel 8.
-    helperSubExports[`./${path.join("helpers", "esm", helperName)}`] = esm;
+    helperSubExports[`./${path.posix.join("helpers", "esm", helperName)}`] =
+      esm;
   }
 
   writeHelperExports(runtimeName, helperSubExports);

test/jestExportsMapResolver.cjs

@@ -0,0 +1,11 @@
+// Temporary workaround for https://github.com/facebook/jest/issues/9771
+// Source: https://github.com/facebook/jest/issues/9771#issuecomment-841624042
+
+const resolver = require("enhanced-resolve").create.sync({
+  conditionNames: ["node", "require", "default"],
+  extensions: [".js", ".json", ".node", ".ts"],
+});
+
+module.exports = function (request, options) {
+  return resolver(options.basedir, request);
+};

yarn.lock

@@ -5749,6 +5749,7 @@ __metadata:
     babel-plugin-transform-charcodes: ^0.2.0
     chalk: ^2.4.2
     charcodes: ^0.2.0
+    enhanced-resolve: ^5.8.2
     eslint: ^7.27.0
     eslint-import-resolver-node: ^0.3.4
     eslint-plugin-flowtype: ^5.7.2
@@ -7445,13 +7446,13 @@ __metadata:
   languageName: node
   linkType: hard
 
-"enhanced-resolve@npm:^5.7.0":
-  version: 5.7.0
-  resolution: "enhanced-resolve@npm:5.7.0"
+"enhanced-resolve@npm:^5.7.0, enhanced-resolve@npm:^5.8.2":
+  version: 5.8.2
+  resolution: "enhanced-resolve@npm:5.8.2"
   dependencies:
     graceful-fs: ^4.2.4
     tapable: ^2.2.0
-  checksum: 545cfa659e9cdccf1240bccbbd1791db7ec589979d71b35df5aeaf872dd8d13fab379ad73fa960f4cb32963b85492792c0fb0866f484043740014824ae6088b9
+  checksum: 1af3f6bcb92e849f6c18d44c427cbdaecac4be61023f2008d2ef0f8a48c909bf13afa9a5c04f9d030f27d9a7e27e40c367caa22cd63d2a7eb5fdbab7579d1538
   languageName: node
   linkType: hard