Improve array destructuring spec compliance

packages/babel-helpers/src/helpers-generated.ts

@@ -45,6 +45,14 @@ export default Object.freeze({
     "7.20.1",
     'export default function _checkInRHS(value){if(Object(value)!==value)throw TypeError("right-hand side of \'in\' should be an object, got "+(null!==value?typeof value:"null"));return value}',
   ),
+  iterableToArrayLimit: helper(
+    "7.0.0-beta.0",
+    'export default function _iterableToArrayLimit(arr,i){var _i=null==arr?null:"undefined"!=typeof Symbol&&arr[Symbol.iterator]||arr["@@iterator"];if(null!=_i){var _s,_e,_x,_r,_arr=[],_n=!0,_d=!1;try{if(_x=(_i=_i.call(arr)).next,0===i){if(Object(_i)!==_i)return;_n=!1}else for(;!(_n=(_s=_x.call(_i)).done)&&(_arr.push(_s.value),_arr.length!==i);_n=!0);}catch(err){_d=!0,_e=err}finally{try{if(!_n&&null!=_i.return&&(_r=_i.return(),Object(_r)!==_r))return}finally{if(_d)throw _e}}return _arr}}',
+  ),
+  iterableToArrayLimitLoose: helper(
+    "7.0.0-beta.0",
+    'export default function _iterableToArrayLimitLoose(arr,i){var _i=arr&&("undefined"!=typeof Symbol&&arr[Symbol.iterator]||arr["@@iterator"]);if(null!=_i){var _s,_arr=[];for(_i=_i.call(arr);arr.length<i&&!(_s=_i.next()).done;)_arr.push(_s.value);return _arr}}',
+  ),
   jsx: helper(
     "7.0.0-beta.0",
     'var REACT_ELEMENT_TYPE;export default function _createRawReactElement(type,props,key,children){REACT_ELEMENT_TYPE||(REACT_ELEMENT_TYPE="function"==typeof Symbol&&Symbol.for&&Symbol.for("react.element")||60103);var defaultProps=type&&type.defaultProps,childrenLength=arguments.length-3;if(props||0===childrenLength||(props={children:void 0}),1===childrenLength)props.children=children;else if(childrenLength>1){for(var childArray=new Array(childrenLength),i=0;i<childrenLength;i++)childArray[i]=arguments[i+3];props.children=childArray}if(props&&defaultProps)for(var propName in defaultProps)void 0===props[propName]&&(props[propName]=defaultProps[propName]);else props||(props=defaultProps||{});return{$$typeof:REACT_ELEMENT_TYPE,type:type,key:void 0===key?null:""+key,ref:null,props:props,_owner:null}}',

packages/babel-helpers/src/helpers.ts

@@ -771,58 +771,6 @@ helpers.iterableToArray = helper("7.0.0-beta.0")`
   }
 `;
 
-helpers.iterableToArrayLimit = helper("7.0.0-beta.0")`
-  export default function _iterableToArrayLimit(arr, i) {
-    // this is an expanded form of \`for...of\` that properly supports abrupt completions of
-    // iterators etc. variable names have been minimised to reduce the size of this massive
-    // helper. sometimes spec compliance is annoying :(
-    //
-    // _n = _iteratorNormalCompletion
-    // _d = _didIteratorError
-    // _e = _iteratorError
-    // _i = _iterator
-    // _s = _step
-
-    var _i = arr == null ? null : (typeof Symbol !== "undefined" && arr[Symbol.iterator] || arr["@@iterator"]);
-    if (_i == null) return;
-
-    var _arr = [];
-    var _n = true;
-    var _d = false;
-    var _s, _e;
-    try {
-      for (_i = _i.call(arr); !(_n = (_s = _i.next()).done); _n = true) {
-        _arr.push(_s.value);
-        if (i && _arr.length === i) break;
-      }
-    } catch (err) {
-      _d = true;
-      _e = err;
-    } finally {
-      try {
-        if (!_n && _i["return"] != null) _i["return"]();
-      } finally {
-        if (_d) throw _e;
-      }
-    }
-    return _arr;
-  }
-`;
-
-helpers.iterableToArrayLimitLoose = helper("7.0.0-beta.0")`
-  export default function _iterableToArrayLimitLoose(arr, i) {
-    var _i = arr && (typeof Symbol !== "undefined" && arr[Symbol.iterator] || arr["@@iterator"]);
-    if (_i == null) return;
-
-    var _arr = [];
-    for (_i = _i.call(arr), _step; !(_step = _i.next()).done;) {
-      _arr.push(_step.value);
-      if (i && _arr.length === i) break;
-    }
-    return _arr;
-  }
-`;
-
 helpers.unsupportedIterableToArray = helper("7.9.0")`
   import arrayLikeToArray from "arrayLikeToArray";
 

packages/babel-helpers/src/helpers/iterableToArrayLimit.js

@@ -0,0 +1,54 @@
+/* @minVersion 7.0.0-beta.0 */
+
+export default function _iterableToArrayLimit(arr, i) {
+  // this is an expanded form of \`for...of\` that properly supports abrupt completions of
+  // iterators etc. variable names have been minimised to reduce the size of this massive
+  // helper. sometimes spec compliance is annoying :(
+  //
+  // _n = _iteratorNormalCompletion
+  // _d = _didIteratorError
+  // _e = _iteratorError
+  // _i = _iterator
+  // _s = _step
+  // _x = _next
+  // _r = _return
+
+  var _i =
+    arr == null
+      ? null
+      : (typeof Symbol !== "undefined" && arr[Symbol.iterator]) ||
+        arr["@@iterator"];
+  if (_i == null) return;
+
+  var _arr = [];
+  var _n = true;
+  var _d = false;
+  var _s, _e, _x, _r;
+  try {
+    _x = (_i = _i.call(arr)).next;
+    if (i === 0) {
+      if (Object(_i) !== _i) return;
+      _n = false;
+    } else {
+      for (; !(_n = (_s = _x.call(_i)).done); _n = true) {
+        _arr.push(_s.value);
+        if (_arr.length === i) break;
+      }
+    }
+  } catch (err) {
+    _d = true;
+    _e = err;
+  } finally {
+    try {
+      if (!_n && _i["return"] != null) {
+        _r = _i["return"]();
+        // eslint-disable-next-line no-unsafe-finally
+        if (Object(_r) !== _r) return;
+      }
+    } finally {
+      // eslint-disable-next-line no-unsafe-finally
+      if (_d) throw _e;
+    }
+  }
+  return _arr;
+}

packages/babel-helpers/src/helpers/iterableToArrayLimitLoose.js

@@ -0,0 +1,16 @@
+/* @minVersion 7.0.0-beta.0 */
+
+export default function _iterableToArrayLimitLoose(arr, i) {
+  var _i =
+    arr &&
+    ((typeof Symbol !== "undefined" && arr[Symbol.iterator]) ||
+      arr["@@iterator"]);
+  if (_i == null) return;
+
+  var _arr = [];
+  var _s;
+  for (_i = _i.call(arr); arr.length < i && !(_s = _i.next()).done; ) {
+    _arr.push(_s.value);
+  }
+  return _arr;
+}

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/check-iterator-return/exec.js

@@ -0,0 +1,41 @@
+expect(() => {
+  var [] = {
+    [Symbol.iterator]: () => {
+      return {
+        return: () => {},
+      };
+    },
+  };
+}).toThrow(TypeError);
+
+expect(() => {
+  var [] = {
+    [Symbol.iterator]: () => {
+      return {
+        return: () => ({}),
+      };
+    },
+  };
+}).not.toThrow();
+
+expect(() => {
+  var [x] = {
+    [Symbol.iterator]: () => {
+      return {
+        next: () => ({ done: false, value: 1 }),
+        return: () => {},
+      };
+    },
+  };
+}).toThrow(TypeError);
+
+expect(() => {
+  var [x] = {
+    [Symbol.iterator]: () => {
+      return {
+        next: () => ({ done: false, value: 1 }),
+        return: () => ({}),
+      };
+    },
+  };
+}).not.toThrow();

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/check-iterator-return/input.js

@@ -0,0 +1,33 @@
+var [] = {
+  [Symbol.iterator]: () => {
+    return {
+      return: () => {},
+    };
+  },
+};
+
+var [] = {
+  [Symbol.iterator]: () => {
+    return {
+      return: () => ({}),
+    };
+  },
+};
+
+var [x] = {
+  [Symbol.iterator]: () => {
+    return {
+      next: () => ({ done: false, value: 1 }),
+      return: () => {},
+    };
+  },
+};
+
+var [x] = {
+  [Symbol.iterator]: () => {
+    return {
+      next: () => ({ done: false, value: 1 }),
+      return: () => ({}),
+    };
+  },
+};

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/check-iterator-return/output.js

@@ -0,0 +1,42 @@
+var _Symbol$iterator = {
+    [Symbol.iterator]: () => {
+      return {
+        return: () => {}
+      };
+    }
+  },
+  _Symbol$iterator2 = babelHelpers.slicedToArray(_Symbol$iterator, 0);
+var _Symbol$iterator3 = {
+    [Symbol.iterator]: () => {
+      return {
+        return: () => ({})
+      };
+    }
+  },
+  _Symbol$iterator4 = babelHelpers.slicedToArray(_Symbol$iterator3, 0);
+var _Symbol$iterator5 = {
+    [Symbol.iterator]: () => {
+      return {
+        next: () => ({
+          done: false,
+          value: 1
+        }),
+        return: () => {}
+      };
+    }
+  },
+  _Symbol$iterator6 = babelHelpers.slicedToArray(_Symbol$iterator5, 1),
+  x = _Symbol$iterator6[0];
+var _Symbol$iterator7 = {
+    [Symbol.iterator]: () => {
+      return {
+        next: () => ({
+          done: false,
+          value: 1
+        }),
+        return: () => ({})
+      };
+    }
+  },
+  _Symbol$iterator8 = babelHelpers.slicedToArray(_Symbol$iterator7, 1),
+  x = _Symbol$iterator8[0];

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/empty-array-pattern/exec.js

@@ -0,0 +1,38 @@
+expect(() => {
+  var [] = null;
+}).toThrow(TypeError);
+
+expect(() => {
+  var [] = 42;
+}).toThrow(TypeError);
+
+expect(() => {
+  var [] = {};
+}).toThrow(TypeError);
+
+expect(() => {
+  var [] = { [Symbol.iterator]: () => {} };
+}).toThrow(TypeError);
+
+expect(() => {
+  var [] = [];
+  var [] = [0, 1, 2];
+  var [] = "foo";
+  var [] = (function*() { throw new Error("Should not throw"); })();
+  var [] = { [Symbol.iterator]: () => ({}) };
+  var [] = { [Symbol.iterator]: () => () => {} };
+  var [] = { [Symbol.iterator]: async function*() {} };
+}).not.toThrow();
+
+var returnCalled = false;
+var [] = {
+  [Symbol.iterator]: () => {
+    return {
+      return: () => {
+        returnCalled = true;
+        return {};
+      },
+    };
+  },
+};
+expect(returnCalled).toStrictEqual(true);

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/empty-array-pattern/input.js

@@ -0,0 +1,24 @@
+var [] = null;
+var [] = 42;
+var [] = {};
+var [] = { [Symbol.iterator]: () => {} };
+
+var [] = [];
+var [] = [0, 1, 2];
+var [] = "foo";
+var [] = (function*() { throw new Error("Should not throw"); })();
+var [] = { [Symbol.iterator]: () => ({}) };
+var [] = { [Symbol.iterator]: () => () => {} };
+var [] = { [Symbol.iterator]: async function*() {} };
+
+var returnCalled = false;
+var [] = {
+  [Symbol.iterator]: () => {
+    return {
+      return: () => {
+        returnCalled = true;
+        return {};
+      },
+    };
+  },
+};

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/empty-array-pattern/output.js

@@ -0,0 +1,61 @@
+var _ref = null,
+  _ref2 = babelHelpers.slicedToArray(_ref, 0);
+var _ = 42,
+  _ref3 = babelHelpers.slicedToArray(_, 0);
+var _ref4 = {},
+  _ref5 = babelHelpers.slicedToArray(_ref4, 0);
+var _Symbol$iterator = {
+    [Symbol.iterator]: () => {}
+  },
+  _Symbol$iterator2 = babelHelpers.slicedToArray(_Symbol$iterator, 0);
+var _ref6 = [0, 1, 2];
+var _foo = "foo",
+  _foo2 = babelHelpers.slicedToArray(_foo, 0);
+var _ref7 = /*#__PURE__*/babelHelpers.regeneratorRuntime().mark(function _callee() {
+    return babelHelpers.regeneratorRuntime().wrap(function _callee$(_context) {
+      while (1) {
+        switch (_context.prev = _context.next) {
+          case 0:
+            throw new Error("Should not throw");
+          case 1:
+          case "end":
+            return _context.stop();
+        }
+      }
+    }, _callee);
+  })(),
+  _ref8 = babelHelpers.slicedToArray(_ref7, 0);
+var _Symbol$iterator3 = {
+    [Symbol.iterator]: () => ({})
+  },
+  _Symbol$iterator4 = babelHelpers.slicedToArray(_Symbol$iterator3, 0);
+var _Symbol$iterator5 = {
+    [Symbol.iterator]: () => () => {}
+  },
+  _Symbol$iterator6 = babelHelpers.slicedToArray(_Symbol$iterator5, 0);
+var _Symbol$iterator7 = {
+    [Symbol.iterator]: /*#__PURE__*/babelHelpers.regeneratorRuntime().mark(function _callee2() {
+      return babelHelpers.regeneratorRuntime().async(function _callee2$(_context2) {
+        while (1) {
+          switch (_context2.prev = _context2.next) {
+            case 0:
+            case "end":
+              return _context2.stop();
+          }
+        }
+      }, _callee2, null, null, Promise);
+    })
+  },
+  _Symbol$iterator8 = babelHelpers.slicedToArray(_Symbol$iterator7, 0);
+var returnCalled = false;
+var _Symbol$iterator9 = {
+    [Symbol.iterator]: () => {
+      return {
+        return: () => {
+          returnCalled = true;
+          return {};
+        }
+      };
+    }
+  },
+  _Symbol$iterator10 = babelHelpers.slicedToArray(_Symbol$iterator9, 0);

packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/init-hole/output.js

@@ -45,7 +45,7 @@ try {
 expect(thrown).toEqual(true);
 try {
   thrown = false;
-  var _ = babelHelpers.toArray(void 0);
+  var _ = babelHelpers.slicedToArray(void 0, 0);
 } catch (e) {
   thrown = true;
 }