Implement skipForOfIteratorClosing assumption (#12496)

packages/babel-core/src/config/validation/options.js

@@ -337,11 +337,12 @@ export const assumptionsNames = new Set<string>([
   "ignoreToPrimitiveHint",
   "iterableIsArray",
   "mutableTemplateObject",
+  "noDocumentAll",
   "pureGetters",
   "setClassMethods",
   "setComputedProperties",
   "setPublicClassFields",
-  "noDocumentAll",
+  "skipForOfIteratorClosing",
 ]);
 
 function getSource(loc: NestingPath): OptionsSource {

packages/babel-plugin-transform-for-of/src/index.js

@@ -6,10 +6,8 @@ import transformWithoutHelper from "./no-helper-implementation";
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const { loose } = options;
-
   {
-    const { assumeArray, allowArrayLike } = options;
+    const { assumeArray, allowArrayLike, loose } = options;
 
     if (loose === true && assumeArray === true) {
       throw new Error(
@@ -35,11 +33,14 @@ export default declare((api, options) => {
     options.assumeArray ??
     // Loose mode is not compatible with 'assumeArray', so we shouldn't read
     // 'iterableIsArray' if 'loose' is true.
-    (!loose && api.assumption("iterableIsArray"));
+    (!options.loose && api.assumption("iterableIsArray"));
 
   const arrayLikeIsIterable =
     options.allowArrayLike ?? api.assumption("arrayLikeIsIterable");
 
+  const skipteratorClosing =
+    api.assumption("skipForOfIteratorClosing") ?? options.loose;
+
   if (iterableIsArray && arrayLikeIsIterable) {
     throw new Error(
       `The "iterableIsArray" and "arrayLikeIsIterable" assumptions are not compatible.`,
@@ -113,16 +114,16 @@ export default declare((api, options) => {
     };
   }
 
-  const buildForOfArray = template(`
+  const buildForOfArray = template`
     for (var KEY = 0, NAME = ARR; KEY < NAME.length; KEY++) BODY;
-  `);
+  `;
 
-  const buildForOfLoose = template.statements(`
+  const buildForOfNoIteratorClosing = template.statements`
     for (var ITERATOR_HELPER = CREATE_ITERATOR_HELPER(OBJECT, ARRAY_LIKE_IS_ITERABLE), STEP_KEY;
         !(STEP_KEY = ITERATOR_HELPER()).done;) BODY;
-  `);
+  `;
 
-  const buildForOf = template.statements(`
+  const buildForOf = template.statements`
     var ITERATOR_HELPER = CREATE_ITERATOR_HELPER(OBJECT, ARRAY_LIKE_IS_ITERABLE), STEP_KEY;
     try {
       for (ITERATOR_HELPER.s(); !(STEP_KEY = ITERATOR_HELPER.n()).done;) BODY;
@@ -131,11 +132,11 @@ export default declare((api, options) => {
     } finally {
       ITERATOR_HELPER.f();
     }
-  `);
+  `;
 
-  const builder = loose
+  const builder = skipteratorClosing
     ? {
-        build: buildForOfLoose,
+        build: buildForOfNoIteratorClosing,
         helper: "createForOfIteratorHelperLoose",
         getContainer: nodes => nodes,
       }
@@ -198,7 +199,7 @@ export default declare((api, options) => {
 
         if (!state.availableHelper(builder.helper)) {
           // Babel <7.9.0 doesn't support this helper
-          transformWithoutHelper(loose, path, state);
+          transformWithoutHelper(skipteratorClosing, path, state);
           return;
         }
 

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/identifier/input.js

@@ -0,0 +1,3 @@
+for (i of arr) {
+
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/identifier/output.js

@@ -0,0 +1,3 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(arr), _step; !(_step = _iterator()).done;) {
+  i = _step.value;
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/ignore-cases/input.js

@@ -0,0 +1,6 @@
+for (var i of foo) {
+  switch (i) {
+    case 1:
+      break;
+  }
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/ignore-cases/output.js

@@ -0,0 +1,8 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(foo), _step; !(_step = _iterator()).done;) {
+  var i = _step.value;
+
+  switch (i) {
+    case 1:
+      break;
+  }
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/let/input.js

@@ -0,0 +1,3 @@
+for (let i of arr) {
+
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/let/output.js

@@ -0,0 +1,3 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(arr), _step; !(_step = _iterator()).done;) {
+  let i = _step.value;
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/member-expression/input.js

@@ -0,0 +1,3 @@
+for (obj.prop of arr) {
+
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/member-expression/output.js

@@ -0,0 +1,3 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(arr), _step; !(_step = _iterator()).done;) {
+  obj.prop = _step.value;
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/multiple/input.js

@@ -0,0 +1,7 @@
+for (var i of arr) {
+
+}
+
+for (var i of numbers) {
+
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/multiple/output.js

@@ -0,0 +1,7 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(arr), _step; !(_step = _iterator()).done;) {
+  var i = _step.value;
+}
+
+for (var _iterator2 = babelHelpers.createForOfIteratorHelperLoose(numbers), _step2; !(_step2 = _iterator2()).done;) {
+  var i = _step2.value;
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/nested-label-for-of/input.js

@@ -0,0 +1,5 @@
+b: for (let c of d()) {
+  for (let e of f()) {
+    continue b;
+  }
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/nested-label-for-of/output.js

@@ -0,0 +1,8 @@
+b: for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(d()), _step; !(_step = _iterator()).done;) {
+  let c = _step.value;
+
+  for (var _iterator2 = babelHelpers.createForOfIteratorHelperLoose(f()), _step2; !(_step2 = _iterator2()).done;) {
+    let e = _step2.value;
+    continue b;
+  }
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    "transform-for-of"
+  ],
+  "assumptions": {
+    "skipForOfIteratorClosing": true
+  }
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/var/input.js

@@ -0,0 +1,3 @@
+for (var i of arr) {
+
+}

packages/babel-plugin-transform-for-of/test/fixtures/assumption-skipForOfIteratorClosing/var/output.js

@@ -0,0 +1,3 @@
+for (var _iterator = babelHelpers.createForOfIteratorHelperLoose(arr), _step; !(_step = _iterator()).done;) {
+  var i = _step.value;
+}