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;
-
-exports.getVersion = sendCached("GET_VERSION");
-
-exports.getTypesInfo = sendCached("GET_TYPES_INFO");
-
-exports.getVisitorKeys = sendCached("GET_VISITOR_KEYS");
-
-exports.getTokLabels = sendCached("GET_TOKEN_LABELS");
-
-exports.maybeParse = (code, options) => send("MAYBE_PARSE", { code, options });
-
-function sendCached(action) {
-  let cache = null;
-
-  return () => {
-    if (!cache) cache = send(action, undefined);
-    return cache;
-  };
+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",
+};
+
+class Client {
+  #send;
+
+  constructor(send) {
+    this.#send = send;
+  }
+
+  #vCache;
+  getVersion() {
+    return (this.#vCache ??= this.#send(ACTIONS.GET_VERSION, undefined));
+  }
+
+  #tiCache;
+  getTypesInfo() {
+    return (this.#tiCache ??= this.#send(ACTIONS.GET_TYPES_INFO, undefined));
+  }
+
+  #vkCache;
+  getVisitorKeys() {
+    return (this.#vkCache ??= this.#send(ACTIONS.GET_VISITOR_KEYS, undefined));
+  }
+
+  #tlCache;
+  getTokLabels() {
+    return (this.#tlCache ??= this.#send(ACTIONS.GET_TOKEN_LABELS, undefined));
+  }
+
+  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.
-  const worker = new Worker(
+// 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"));
+  }
+
+  #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();
-
-  const signal = new Int32Array(new SharedArrayBuffer(4));
-
-  send = (action, payload) => {
-    signal[0] = 0;
-    const subChannel = new MessageChannel();
-
-    worker.postMessage({ signal, port: subChannel.port1, action, payload }, [
-      subChannel.port1,
-    ]);
-
-    Atomics.wait(signal, 0, 0);
-    const { message } = receiveMessageOnPort(subChannel.port2);
-
-    if (message.error) throw Object.assign(message.error, message.errorData);
-    else return message.result;
+  #signal = new Int32Array(new SharedArrayBuffer(4));
+
+  constructor() {
+    super((action, payload) => {
+      this.#signal[0] = 0;
+      const subChannel = new WorkerClient.#worker_threads.MessageChannel();
+
+      this.#worker.postMessage(
+        { signal: this.#signal, port: subChannel.port1, action, payload },
+        [subChannel.port1],
+      );
+
+      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);
+  }
+};