Fix _step.value access in for await (#13491)

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

@@ -2,26 +2,22 @@ import { types as t, template } from "@babel/core";
 
 const buildForAwait = template(`
   async function wrapper() {
-    var ITERATOR_COMPLETION = true;
+    var ITERATOR_ABRUPT_COMPLETION = false;
     var ITERATOR_HAD_ERROR_KEY = false;
     var ITERATOR_ERROR_KEY;
     try {
       for (
-        var ITERATOR_KEY = GET_ITERATOR(OBJECT), STEP_KEY, STEP_VALUE;
+        var ITERATOR_KEY = GET_ITERATOR(OBJECT), STEP_KEY;
-        (
+        ITERATOR_ABRUPT_COMPLETION = !(STEP_KEY = await ITERATOR_KEY.next()).done;
-          STEP_KEY = await ITERATOR_KEY.next(),
+        ITERATOR_ABRUPT_COMPLETION = false
-          ITERATOR_COMPLETION = STEP_KEY.done,
+      ) {
-          STEP_VALUE = await STEP_KEY.value,
-          !ITERATOR_COMPLETION
-        );
-        ITERATOR_COMPLETION = true) {
       }
     } catch (err) {
       ITERATOR_HAD_ERROR_KEY = true;
       ITERATOR_ERROR_KEY = err;
     } finally {
       try {
-        if (!ITERATOR_COMPLETION && ITERATOR_KEY.return != null) {
+        if (ITERATOR_ABRUPT_COMPLETION && ITERATOR_KEY.return != null) {
           await ITERATOR_KEY.return();
         }
       } finally {
@@ -37,7 +33,7 @@ export default function (path, { getAsyncIterator }) {
   const { node, scope, parent } = path;
 
   const stepKey = scope.generateUidIdentifier("step");
-  const stepValue = scope.generateUidIdentifier("value");
+  const stepValue = t.memberExpression(stepKey, t.identifier("value"));
   const left = node.left;
   let declar;
 
@@ -54,15 +50,14 @@ export default function (path, { getAsyncIterator }) {
   }
   let template = buildForAwait({
     ITERATOR_HAD_ERROR_KEY: scope.generateUidIdentifier("didIteratorError"),
-    ITERATOR_COMPLETION: scope.generateUidIdentifier(
+    ITERATOR_ABRUPT_COMPLETION: scope.generateUidIdentifier(
-      "iteratorNormalCompletion",
+      "iteratorAbruptCompletion",
     ),
     ITERATOR_ERROR_KEY: scope.generateUidIdentifier("iteratorError"),
     ITERATOR_KEY: scope.generateUidIdentifier("iterator"),
     GET_ITERATOR: getAsyncIterator,
     OBJECT: node.right,
-    STEP_VALUE: t.cloneNode(stepValue),
+    STEP_KEY: t.cloneNode(stepKey),
-    STEP_KEY: stepKey,
   });
 
   // remove async function wrapper

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-arrow/output.js

@@ -1,13 +1,13 @@
 /*#__PURE__*/
 babelHelpers.asyncToGenerator(function* () {
-  var _iteratorNormalCompletion = true;
+  var _iteratorAbruptCompletion = false;
   var _didIteratorError = false;
 
   var _iteratorError;
 
   try {
-    for (var _iterator = babelHelpers.asyncIterator(y), _step, _value; _step = yield _iterator.next(), _iteratorNormalCompletion = _step.done, _value = yield _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+    for (var _iterator = babelHelpers.asyncIterator(y), _step; _iteratorAbruptCompletion = !(_step = yield _iterator.next()).done; _iteratorAbruptCompletion = false) {
-      let x = _value;
+      let x = _step.value;
       f(x);
     }
   } catch (err) {
@@ -15,7 +15,7 @@ babelHelpers.asyncToGenerator(function* () {
     _iteratorError = err;
   } finally {
     try {
-      if (!_iteratorNormalCompletion && _iterator.return != null) {
+      if (_iteratorAbruptCompletion && _iterator.return != null) {
         yield _iterator.return();
       }
     } finally {

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

@@ -1,19 +1,19 @@
 async function foo() {
-  var _iteratorNormalCompletion = true;
+  var _iteratorAbruptCompletion = false;
   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) {
+    for (var _iterator = babelHelpers.asyncIterator(y), _step; _iteratorAbruptCompletion = !(_step = await _iterator.next()).done; _iteratorAbruptCompletion = false) {
-      const x = _value;
+      const x = _step.value;
     }
   } catch (err) {
     _didIteratorError = true;
     _iteratorError = err;
   } finally {
     try {
-      if (!_iteratorNormalCompletion && _iterator.return != null) {
+      if (_iteratorAbruptCompletion && _iterator.return != null) {
         await _iterator.return();
       }
     } finally {

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-function/output.js

@@ -4,14 +4,14 @@ function f() {
 
 function _f() {
   _f = babelHelpers.asyncToGenerator(function* () {
-    var _iteratorNormalCompletion = true;
+    var _iteratorAbruptCompletion = false;
     var _didIteratorError = false;
 
     var _iteratorError;
 
     try {
-      for (var _iterator = babelHelpers.asyncIterator(y), _step, _value; _step = yield _iterator.next(), _iteratorNormalCompletion = _step.done, _value = yield _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+      for (var _iterator = babelHelpers.asyncIterator(y), _step; _iteratorAbruptCompletion = !(_step = yield _iterator.next()).done; _iteratorAbruptCompletion = false) {
-        let x = _value;
+        let x = _step.value;
         g(x);
       }
     } catch (err) {
@@ -19,7 +19,7 @@ function _f() {
       _iteratorError = err;
     } finally {
       try {
-        if (!_iteratorNormalCompletion && _iterator.return != null) {
+        if (_iteratorAbruptCompletion && _iterator.return != null) {
           yield _iterator.return();
         }
       } finally {

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/async-generator/output.js

@@ -4,14 +4,14 @@ function g() {
 
 function _g() {
   _g = babelHelpers.wrapAsyncGenerator(function* () {
-    var _iteratorNormalCompletion = true;
+    var _iteratorAbruptCompletion = false;
     var _didIteratorError = false;
 
     var _iteratorError;
 
     try {
-      for (var _iterator = babelHelpers.asyncIterator(y), _step, _value; _step = yield babelHelpers.awaitAsyncGenerator(_iterator.next()), _iteratorNormalCompletion = _step.done, _value = yield babelHelpers.awaitAsyncGenerator(_step.value), !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+      for (var _iterator = babelHelpers.asyncIterator(y), _step; _iteratorAbruptCompletion = !(_step = yield babelHelpers.awaitAsyncGenerator(_iterator.next())).done; _iteratorAbruptCompletion = false) {
-        let x = _value;
+        let x = _step.value;
         f(x);
       }
     } catch (err) {
@@ -19,7 +19,7 @@ function _g() {
       _iteratorError = err;
     } finally {
       try {
-        if (!_iteratorNormalCompletion && _iterator.return != null) {
+        if (_iteratorAbruptCompletion && _iterator.return != null) {
           yield babelHelpers.awaitAsyncGenerator(_iterator.return());
         }
       } finally {

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/destructuring/output.js

@@ -4,17 +4,17 @@ function f() {
 
 function _f() {
   _f = babelHelpers.asyncToGenerator(function* () {
-    var _iteratorNormalCompletion = true;
+    var _iteratorAbruptCompletion = false;
     var _didIteratorError = false;
 
     var _iteratorError;
 
     try {
-      for (var _iterator = babelHelpers.asyncIterator(a), _step, _value; _step = yield _iterator.next(), _iteratorNormalCompletion = _step.done, _value = yield _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+      for (var _iterator = babelHelpers.asyncIterator(a), _step; _iteratorAbruptCompletion = !(_step = yield _iterator.next()).done; _iteratorAbruptCompletion = false) {
         let {
           x,
           y: [z]
-        } = _value;
+        } = _step.value;
         g(x, z);
       }
     } catch (err) {
@@ -22,7 +22,7 @@ function _f() {
       _iteratorError = err;
     } finally {
       try {
-        if (!_iteratorNormalCompletion && _iterator.return != null) {
+        if (_iteratorAbruptCompletion && _iterator.return != null) {
           yield _iterator.return();
         }
       } finally {

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/lhs-member-expression/exec.js

@@ -0,0 +1,6 @@
+return async function () {
+  let obj = {};
+  for await (obj.x of [1, 2]);
+
+  expect(obj.x).toBe(2);
+}();

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/lhs-member-expression/input.js

@@ -0,0 +1,3 @@
+(async function () {
+  for await (obj.x of y) {}
+})();

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/lhs-member-expression/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/lhs-member-expression/output.js

@@ -0,0 +1,25 @@
+babelHelpers.asyncToGenerator(function* () {
+  var _iteratorAbruptCompletion = false;
+  var _didIteratorError = false;
+
+  var _iteratorError;
+
+  try {
+    for (var _iterator = babelHelpers.asyncIterator(y), _step; _iteratorAbruptCompletion = !(_step = yield _iterator.next()).done; _iteratorAbruptCompletion = false) {
+      obj.x = _step.value;
+    }
+  } catch (err) {
+    _didIteratorError = true;
+    _iteratorError = err;
+  } finally {
+    try {
+      if (_iteratorAbruptCompletion && _iterator.return != null) {
+        yield _iterator.return();
+      }
+    } finally {
+      if (_didIteratorError) {
+        throw _iteratorError;
+      }
+    }
+  }
+})();

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-single-tick/exec.js

@@ -0,0 +1,31 @@
+let resolve;
+let promise = new Promise((r) => (resolve = r));
+let iterable = {
+  [Symbol.asyncIterator || "@@asyncIterator"]() {
+    return {
+      next: () => promise,
+    };
+  },
+};
+
+let values = [];
+
+return Promise.all([
+  async function () {
+    for await (let value of iterable) {
+      values.push(value);
+    }
+  }(),
+  async function () {
+    resolve({ value: 0, done: false });
+    promise = new Promise((r) => (resolve = r));
+
+    await null;
+    resolve({ value: 1, done: false });
+    promise = new Promise((r) => (resolve = r));
+
+    resolve({ value: undefined, done: true });
+  }(),
+]).then(() => {
+  expect(values).toEqual([0, 1]);
+});

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-single-tick/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-value-is-promise/exec.js

@@ -0,0 +1,22 @@
+let steps = [
+  { done: false, value: Promise.resolve(1) },
+  { done: true, value: undefined }
+];
+
+let iterable = {
+  [Symbol.asyncIterator || "@@asyncIterator"]() {
+    return {
+      next: () => steps.shift(),
+    };
+  },
+};
+
+let values = [];
+
+return async function () {
+  let value;
+  for await (value of iterable);
+
+  expect(value).toBeInstanceOf(Promise);
+  await expect(value).resolves.toBe(1);
+}();

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-value-is-promise/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-value-not-accessed-when-done/exec.js

@@ -0,0 +1,18 @@
+let gotValue = false;
+
+let iterable = {
+  [Symbol.asyncIterator || "@@asyncIterator"]() {
+    return {
+      next: () => Promise.resolve({
+        get value() { gotValue = true },
+        done: true
+      })
+    };
+  },
+};
+
+return async function () {
+  for await (let value of iterable) {}
+
+  expect(gotValue).toBe(false);
+}();

packages/babel-plugin-proposal-async-generator-functions/test/fixtures/for-await/step-value-not-accessed-when-done/options.json

@@ -0,0 +1,5 @@
+{
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

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

@@ -1,21 +1,20 @@
 (async () => {
-  var _iteratorNormalCompletion = true;
+  var _iteratorAbruptCompletion = false;
   var _didIteratorError = false;
 
   var _iteratorError;
 
   try {
-    for (var _iterator = babelHelpers.asyncIterator(iterable), _step, _value; _step = await _iterator.next(), _iteratorNormalCompletion = _step.done, _value = await _step.value, !_iteratorNormalCompletion; _iteratorNormalCompletion = true) {
+    for (var _iterator = babelHelpers.asyncIterator(iterable), _step; _iteratorAbruptCompletion = !(_step = await _iterator.next()).done; _iteratorAbruptCompletion = false) {
-      const _value2 = _value,
+      const _step$value = babelHelpers.slicedToArray(_step.value, 1),
-            _value3 = babelHelpers.slicedToArray(_value2, 1),
+            value = _step$value[0];
-            value = _value3[0];
     }
   } catch (err) {
     _didIteratorError = true;
     _iteratorError = err;
   } finally {
     try {
-      if (!_iteratorNormalCompletion && _iterator.return != null) {
+      if (_iteratorAbruptCompletion && _iterator.return != null) {
         await _iterator.return();
       }
     } finally {