[babel 8] Move @babel/register transform to a separate worker (#14025)

packages/babel-node/test/fixtures/cli/--config-file/in-files/index.js

@@ -1 +1,3 @@
-console.log("foo");
+// See https://github.com/babel/babel/pull/14025#issuecomment-986296424
+// for the reason behind using setImmediate.
+setImmediate(() => console.log("foo"));

packages/babel-node/test/fixtures/cli/--env-name/in-files/index.js

@@ -1 +1,3 @@
-console.log("foo");
+// See https://github.com/babel/babel/pull/14025#issuecomment-986296424
+// for the reason behind using setImmediate.
+setImmediate(() => console.log("foo"));

packages/babel-node/test/fixtures/cli/--presets/in-files/index.js

@@ -1 +1,3 @@
-console.log("foo");
+// See https://github.com/babel/babel/pull/14025#issuecomment-986296424
+// for the reason behind using setImmediate.
+setImmediate(() => console.log("foo"));

packages/babel-node/test/fixtures/cli/-b/in-files/index.js

@@ -1 +1,3 @@
-console.log("foo");
+// See https://github.com/babel/babel/pull/14025#issuecomment-986296424
+// for the reason behind using setImmediate.
+setImmediate(() => console.log("foo"));

packages/babel-register/.npmignore

@@ -1,3 +1,7 @@
 src
 test
 *.log
+
+experimental-worker.js
+lib/experimental-worker.js
+lib/is-in-register-worker.js

packages/babel-register/experimental-worker.js

@@ -0,0 +1 @@
+module.exports = require("./lib/experimental-worker");

packages/babel-register/package.json

@@ -12,9 +12,10 @@
     "directory": "packages/babel-register"
   },
   "author": "The Babel Team (https://babel.dev/team)",
+  "type": "commonjs",
   "main": "./lib/index.js",
   "browser": {
-    "./lib/nodeWrapper.js": "./lib/browser.js"
+    "./lib/index.js": "./lib/browser.js"
   },
   "dependencies": {
     "clone-deep": "^4.0.1",
@@ -28,6 +29,7 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
+    "@babel/plugin-transform-arrow-functions": "workspace:^",
     "@babel/plugin-transform-modules-commonjs": "workspace:^",
     "browserify": "^16.5.2"
   },

packages/babel-register/src/browser.js

@@ -0,0 +1,10 @@
+// required to safely use babel/register within a browserify codebase
+
+function register() {}
+
+module.exports = Object.assign(register, {
+  default: register,
+  register,
+  revert: function revert() {},
+  __esModule: true,
+});

packages/babel-register/src/cache.js

@@ -0,0 +1,3 @@
+// File moved to ./worker/cache.js
+// TODO: Remove this backward-compat "proxy file" in Babel 8
+module.exports = require("./worker/cache");

packages/babel-register/src/experimental-worker.js

@@ -0,0 +1,26 @@
+// TODO: Move this file to index.js in Babel 8
+
+"use strict";
+
+const [major, minor] = process.versions.node.split(".").map(Number);
+
+if (major < 12 || (major === 12 && minor < 3)) {
+  throw new Error(
+    "@babel/register/experimental-worker requires Node.js >= 12.3.0",
+  );
+}
+
+const hook = require("./hook");
+const { WorkerClient } = require("./worker-client");
+
+const register = hook.register.bind(null, new WorkerClient());
+
+module.exports = Object.assign(register, {
+  revert: hook.revert,
+  default: register,
+  __esModule: true,
+});
+
+if (!require("./is-in-register-worker").isInRegisterWorker) {
+  register();
+}

packages/babel-register/src/hook.js

@@ -0,0 +1,85 @@
+"use strict";
+
+const { addHook } = require("pirates");
+const sourceMapSupport = require("source-map-support");
+
+let piratesRevert;
+const maps = Object.create(null);
+
+function installSourceMapSupport() {
+  installSourceMapSupport = () => {}; // eslint-disable-line no-func-assign
+
+  sourceMapSupport.install({
+    handleUncaughtExceptions: false,
+    environment: "node",
+    retrieveSourceMap(filename) {
+      const map = maps?.[filename];
+      if (map) {
+        return { url: null, map: map };
+      } else {
+        return null;
+      }
+    },
+  });
+}
+
+if (!process.env.BABEL_8_BREAKING) {
+  // Babel 7 compiles files in the same thread where it hooks `require()`,
+  // so we must prevent mixing Babel plugin dependencies with the files
+  // to be compiled.
+  // All the `!process.env.BABEL_8_BREAKING` code in this file is for
+  // this purpose.
+
+  const Module = require("module");
+
+  let compiling = false;
+  const internalModuleCache = Module._cache;
+
+  // eslint-disable-next-line no-var
+  var compileBabel7 = function compileBabel7(client, code, filename) {
+    if (!client.isLocalClient) return compile(client, code, filename);
+
+    if (compiling) return code;
+
+    const globalModuleCache = Module._cache;
+    try {
+      compiling = true;
+      Module._cache = internalModuleCache;
+      return compile(client, code, filename);
+    } finally {
+      compiling = false;
+      Module._cache = globalModuleCache;
+    }
+  };
+}
+
+function compile(client, inputCode, filename) {
+  const result = client.transform(inputCode, filename);
+
+  if (result === null) return inputCode;
+
+  const { code, map } = result;
+  if (map) {
+    maps[filename] = map;
+    installSourceMapSupport();
+  }
+  return code;
+}
+
+exports.register = function register(client, opts = {}) {
+  if (piratesRevert) piratesRevert();
+
+  piratesRevert = addHook(
+    (process.env.BABEL_8_BREAKING ? compile : compileBabel7).bind(null, client),
+    {
+      exts: opts.extensions ?? client.getDefaultExtensions(),
+      ignoreNodeModules: false,
+    },
+  );
+
+  client.setOptions(opts);
+};
+
+exports.revert = function revert() {
+  if (piratesRevert) piratesRevert();
+};

packages/babel-register/src/index.js

@@ -4,12 +4,16 @@
  * from a compiled Babel import.
  */
 
-exports = module.exports = function (...args) {
-  return register(...args);
-};
-exports.__esModule = true;
+if (process.env.BABEL_8_BREAKING) {
+  module.exports = require("./experimental-worker");
+} else {
+  exports = module.exports = function (...args) {
+    return register(...args);
+  };
+  exports.__esModule = true;
 
-const node = require("./nodeWrapper");
-const register = node.default;
+  const node = require("./nodeWrapper");
+  const register = node.default;
 
-Object.assign(exports, node);
+  Object.assign(exports, node);
+}

packages/babel-register/src/is-in-register-worker.js

@@ -0,0 +1,20 @@
+"use strict";
+
+/**
+ * Since workers inherit the exec options from the parent thread, we
+ * must be careful to avoid infite "@babel/register" setup loops.
+ *
+ * If @babel/register is imported using the -r/--require flag, the worker
+ * will have the same flag and we must avoid registering the @babel/register
+ * hook again.
+ *
+ * - markInRegisterWorker() can be used to mark a set of env vars (that will
+ *   be forwarded to a worker) as being in the @babel/register worker.
+ * - isInRegisterWorker will be true in @babel/register workers.
+ */
+
+const envVarName = "___INTERNAL___IS_INSIDE_BABEL_REGISTER_WORKER___";
+const envVarValue = "yes_I_am";
+
+exports.markInRegisterWorker = env => ({ ...env, [envVarName]: envVarValue });
+exports.isInRegisterWorker = process.env[envVarName] === envVarValue;

packages/babel-register/src/node.js

@@ -0,0 +1,13 @@
+// TODO: Remove this file in Babel 8
+
+"use strict";
+
+const hook = require("./hook");
+const { LocalClient } = require("./worker-client");
+
+const register = hook.register.bind(null, new LocalClient());
+
+module.exports = Object.assign(register, {
+  revert: hook.revert,
+  default: register,
+});