Always transform for-await in async functions. (#7446)

for-await was transformed in @babel/helper-remap-async-to-generator, which was
called by @babel/plugin-transform-async-to-generator and
@babel/plugin-proposal-async-generator-functions. This prevented for-await
statements in async functions to be transpiled if the
transform-async-to-generator plugin was't enabled.

packages/babel-helper-remap-async-to-generator/src/index.js

@@ -4,7 +4,6 @@ import type { NodePath } from "@babel/traverse";
 import wrapFunction from "@babel/helper-wrap-function";
 import annotateAsPure from "@babel/helper-annotate-as-pure";
 import * as t from "@babel/types";
-import rewriteForAwait from "./for-await";
 
 const awaitVisitor = {
   Function(path) {
@@ -27,44 +26,13 @@ const awaitVisitor = {
       ),
     );
   },
-
-  ForOfStatement(path, { file, wrapAwait }) {
-    const { node } = path;
-    if (!node.await) return;
-
-    const build = rewriteForAwait(path, {
-      getAsyncIterator: file.addHelper("asyncIterator"),
-      wrapAwait,
-    });
-
-    const { declar, loop } = build;
-    const block = loop.body;
-
-    // ensure that it's a block so we can take all its statements
-    path.ensureBlock();
-
-    // add the value declaration to the new loop body
-    if (declar) {
-      block.body.push(declar);
-    }
-
-    // push the rest of the original loop body onto our new body
-    block.body = block.body.concat(node.body.body);
-
-    t.inherits(loop, node);
-    t.inherits(loop.body, node.body);
-
-    if (build.replaceParent) {
-      path.parentPath.replaceWithMultiple(build.node);
-    } else {
-      path.replaceWithMultiple(build.node);
-    }
-  },
 };
 
-export default function(path: NodePath, file: Object, helpers: Object) {
+export default function(
+  path: NodePath,
+  helpers: { wrapAsync: Object, wrapAwait: Object },
+) {
   path.traverse(awaitVisitor, {
-    file,
     wrapAwait: helpers.wrapAwait,
   });
 

packages/babel-plugin-proposal-async-generator-functions/package.json

@@ -18,6 +18,8 @@
   },
   "devDependencies": {
     "@babel/core": "7.0.0-beta.40",
+    "@babel/types": "7.0.0-beta.40",
+    "@babel/template": "7.0.0-beta.40",
     "@babel/helper-plugin-test-runner": "7.0.0-beta.40"
   }
 }

packages/babel-plugin-proposal-async-generator-functions/src/for-await.js

@@ -1,8 +1,8 @@
 import * as t from "@babel/types";
 import template from "@babel/template";
 
-const awaitTemplate = `
+const buildForAwait = template(`
-  function* wrapper() {
+  async function wrapper() {
     var ITERATOR_COMPLETION = true;
     var ITERATOR_HAD_ERROR_KEY = false;
     var ITERATOR_ERROR_KEY;
@@ -10,9 +10,9 @@ const awaitTemplate = `
       for (
         var ITERATOR_KEY = GET_ITERATOR(OBJECT), STEP_KEY, STEP_VALUE;
         (
-          STEP_KEY = yield AWAIT(ITERATOR_KEY.next()),
+          STEP_KEY = await ITERATOR_KEY.next(),
           ITERATOR_COMPLETION = STEP_KEY.done,
-          STEP_VALUE = yield AWAIT(STEP_KEY.value),
+          STEP_VALUE = await STEP_KEY.value,
           !ITERATOR_COMPLETION
         );
         ITERATOR_COMPLETION = true) {
@@ -23,7 +23,7 @@ const awaitTemplate = `
     } finally {
       try {
         if (!ITERATOR_COMPLETION && ITERATOR_KEY.return != null) {
-          yield AWAIT(ITERATOR_KEY.return());
+          await ITERATOR_KEY.return();
         }
       } finally {
         if (ITERATOR_HAD_ERROR_KEY) {
@@ -32,13 +32,9 @@ const awaitTemplate = `
       }
     }
   }
-`;
+`);
-const buildForAwait = template(awaitTemplate);
-const buildForAwaitWithoutWrapping = template(
-  awaitTemplate.replace(/\bAWAIT\b/g, ""),
-);
 
-export default function(path, { getAsyncIterator, wrapAwait }) {
+export default function(path, { getAsyncIterator }) {
   const { node, scope, parent } = path;
 
   const stepKey = scope.generateUidIdentifier("step");
@@ -57,9 +53,7 @@ export default function(path, { getAsyncIterator, wrapAwait }) {
       t.variableDeclarator(left.declarations[0].id, stepValue),
     ]);
   }
-
+  let template = buildForAwait({
-  const build = wrapAwait ? buildForAwait : buildForAwaitWithoutWrapping;
-  let template = build({
     ITERATOR_HAD_ERROR_KEY: scope.generateUidIdentifier("didIteratorError"),
     ITERATOR_COMPLETION: scope.generateUidIdentifier(
       "iteratorNormalCompletion",
@@ -70,10 +64,9 @@ export default function(path, { getAsyncIterator, wrapAwait }) {
     OBJECT: node.right,
     STEP_VALUE: stepValue,
     STEP_KEY: stepKey,
-    ...(wrapAwait ? { AWAIT: wrapAwait } : {}),
   });
 
-  // remove generator function wrapper
+  // remove async function wrapper
   template = template.body.body;
 
   const isLabeledParent = t.isLabeledStatement(parent);

packages/babel-plugin-proposal-async-generator-functions/src/index.js

@@ -2,6 +2,7 @@ import { declare } from "@babel/helper-plugin-utils";
 import remapAsyncToGenerator from "@babel/helper-remap-async-to-generator";
 import syntaxAsyncGenerators from "@babel/plugin-syntax-async-generators";
 import { types as t } from "@babel/core";
+import rewriteForAwait from "./for-await";
 
 export default declare(api => {
   api.assertVersion(7);
@@ -21,18 +22,73 @@ export default declare(api => {
     },
   };
 
+  const forAwaitVisitor = {
+    Function(path) {
+      path.skip();
+    },
+
+    ForOfStatement(path, { file }) {
+      const { node } = path;
+      if (!node.await) return;
+
+      const build = rewriteForAwait(path, {
+        getAsyncIterator: file.addHelper("asyncIterator"),
+      });
+
+      const { declar, loop } = build;
+      const block = loop.body;
+
+      // ensure that it's a block so we can take all its statements
+      path.ensureBlock();
+
+      // add the value declaration to the new loop body
+      if (declar) {
+        block.body.push(declar);
+      }
+
+      // push the rest of the original loop body onto our new body
+      block.body = block.body.concat(node.body.body);
+
+      t.inherits(loop, node);
+      t.inherits(loop.body, node.body);
+
+      if (build.replaceParent) {
+        path.parentPath.replaceWithMultiple(build.node);
+      } else {
+        path.replaceWithMultiple(build.node);
+      }
+    },
+  };
+
+  const visitor = {
+    Function(path, state) {
+      if (!path.node.async) return;
+
+      path.traverse(forAwaitVisitor, state);
+
+      if (!path.node.generator) return;
+
+      path.traverse(yieldStarVisitor, state);
+
+      remapAsyncToGenerator(path, {
+        wrapAsync: state.addHelper("wrapAsyncGenerator"),
+        wrapAwait: state.addHelper("awaitAsyncGenerator"),
+      });
+    },
+  };
+
   return {
     inherits: syntaxAsyncGenerators,
     visitor: {
-      Function(path, state) {
+      Program(path, state) {
-        if (!path.node.async || !path.node.generator) return;
+        // We need to traverse the ast here (instead of just vising Function
-
+        // in the top level visitor) because for-await needs to run before the
-        path.traverse(yieldStarVisitor, state);
+        // async-to-generator plugin. This is because for-await is transpiled
-
+        // using "await" expressions, which are then converted to "yield".
-        remapAsyncToGenerator(path, state.file, {
+        //
-          wrapAsync: state.addHelper("wrapAsyncGenerator"),
+        // This is bad for performance, but plugin ordering will allow as to
-          wrapAwait: state.addHelper("awaitAsyncGenerator"),
+        // directly visit Function in the top level visitor.
-        });
+        path.traverse(visitor, state);
       },
     },
   };

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-function-no-transform/input.js

@@ -0,0 +1,3 @@
+async function foo() {
+	for await (const x of y) {}
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-function-no-transform/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "external-helpers",
+    "proposal-async-generator-functions"
+  ]
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-function-no-transform/output.js

@@ -0,0 +1,25 @@
+async function foo() {
+  var _iteratorNormalCompletion = true;
+  var _didIteratorError = false;
+
+  var _iteratorError;
+
+  try {
+    for (var _iterator = babelHelpers.asyncIterator(y), _step, _value; _step = await _iterator.next(), _iteratorNormalCompletion = _step.done, _value = await _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+      const x = _value;
+    }
+  } catch (err) {
+    _didIteratorError = true;
+    _iteratorError = err;
+  } finally {
+    try {
+      if (!_iteratorNormalCompletion && _iterator.return != null) {
+        await _iterator.return();
+      }
+    } finally {
+      if (_didIteratorError) {
+        throw _iteratorError;
+      }
+    }
+  }
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/regression/5880/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "external-helpers",
+    "proposal-async-generator-functions",
+    "transform-destructuring"
+  ]
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/regression/5880/output.js

@@ -1,11 +1,11 @@
-babelHelpers.asyncToGenerator(function* () {
+(async () => {
   var _iteratorNormalCompletion = true;
   var _didIteratorError = false;
 
   var _iteratorError;
 
   try {
-    for (var _iterator = babelHelpers.asyncIterator(iterable), _step, _value; _step = yield _iterator.next(), _iteratorNormalCompletion = _step.done, _value = yield _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+    for (var _iterator = babelHelpers.asyncIterator(iterable), _step, _value; _step = await _iterator.next(), _iteratorNormalCompletion = _step.done, _value = await _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
       const _value2 = _value,
             _value3 = babelHelpers.slicedToArray(_value2, 1),
             value = _value3[0];
@@ -16,7 +16,7 @@ babelHelpers.asyncToGenerator(function* () {
   } finally {
     try {
       if (!_iteratorNormalCompletion && _iterator.return != null) {
-        yield _iterator.return();
+        await _iterator.return();
       }
     } finally {
       if (_didIteratorError) {

packages/babel-plugin-transform-async-to-generator/src/index.js

@@ -21,9 +21,7 @@ export default declare((api, options) => {
             wrapAsync = state.methodWrapper = addNamed(path, method, module);
           }
 
-          remapAsyncToGenerator(path, state.file, {
+          remapAsyncToGenerator(path, { wrapAsync });
-            wrapAsync,
-          });
         },
       },
     };
@@ -34,7 +32,7 @@ export default declare((api, options) => {
       Function(path, state) {
         if (!path.node.async || path.node.generator) return;
 
-        remapAsyncToGenerator(path, state.file, {
+        remapAsyncToGenerator(path, {
           wrapAsync: state.addHelper("asyncToGenerator"),
         });
       },

packages/babel-plugin-transform-async-to-generator/test/fixtures/regression/5880/options.json

@@ -1,8 +0,0 @@
-{
-  "plugins": [
-    "external-helpers",
-    "transform-async-to-generator",
-    "transform-destructuring",
-    "syntax-async-generators"
-  ]
-}

packages/babel-preset-env/test/fixtures/preset-options/shippedProposals-use-builtins-entry/output.js

@@ -1,3 +1,9 @@
+function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
+
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
+
 function _awaitAsyncGenerator(value) { return new _AwaitValue(value); }
 
 function _wrapAsyncGenerator(fn) { return function () { return new _AsyncGenerator(fn.apply(this, arguments)); }; }
@@ -14,12 +20,6 @@ _AsyncGenerator.prototype.return = function (arg) { return this._invoke("return"
 
 function _AwaitValue(value) { this.wrapped = value; }
 
-function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
-
-function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
-
-function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
-
 var _x$y$a$b = {
   x: 1,
   y: 2,

packages/babel-preset-env/test/fixtures/preset-options/shippedProposals-use-builtins-usage/output.js

@@ -1,16 +1,22 @@
 "use strict";
 
+require("core-js/modules/es6.array.for-each");
+
+require("core-js/modules/es6.array.filter");
+
+require("core-js/modules/es6.array.index-of");
+
 require("regenerator-runtime/runtime");
 
 require("core-js/modules/es6.symbol");
 
 require("core-js/modules/es6.promise");
 
-require("core-js/modules/es6.array.for-each");
+function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
 
-require("core-js/modules/es6.array.filter");
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
 
-require("core-js/modules/es6.array.index-of");
+function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
 
 function _awaitAsyncGenerator(value) { return new _AwaitValue(value); }
 
@@ -28,12 +34,6 @@ _AsyncGenerator.prototype.return = function (arg) { return this._invoke("return"
 
 function _AwaitValue(value) { this.wrapped = value; }
 
-function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
-
-function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
-
-function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
-
 var _x$y$a$b = {
   x: 1,
   y: 2,

packages/babel-preset-env/test/fixtures/preset-options/shippedProposals/output.js

@@ -1,3 +1,9 @@
+function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
+
+function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+
+function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
+
 function _awaitAsyncGenerator(value) { return new _AwaitValue(value); }
 
 function _wrapAsyncGenerator(fn) { return function () { return new _AsyncGenerator(fn.apply(this, arguments)); }; }
@@ -14,12 +20,6 @@ _AsyncGenerator.prototype.return = function (arg) { return this._invoke("return"
 
 function _AwaitValue(value) { this.wrapped = value; }
 
-function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; var ownKeys = Object.keys(source); if (typeof Object.getOwnPropertySymbols === 'function') { ownKeys = ownKeys.concat(Object.getOwnPropertySymbols(source).filter(function (sym) { return Object.getOwnPropertyDescriptor(source, sym).enumerable; })); } ownKeys.forEach(function (key) { _defineProperty(target, key, source[key]); }); } return target; }
-
-function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
-
-function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }
-
 var _x$y$a$b = {
   x: 1,
   y: 2,