vaoid being greedy when destructuring array iterables

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 Gaps between patch versions are faulty/broken releases.
 
+## 2.0.4
+
+ * Avoid being greedy when destructuring array iterables.
+
 ## 2.0.3
 
  * Hoist function declarations in system module formatter for circular references.

lib/6to5/file.js

@@ -22,6 +22,7 @@ File.declarations = [
   "tagged-template-literal",
   "interop-require",
   "to-array",
+  "sliced-to-array",
   "object-without-properties",
   "has-own",
   "slice"
@@ -82,13 +83,19 @@ File.normaliseOptions = function (opts) {
   return opts;
 };
 
-File.prototype.toArray = function (node) {
+File.prototype.toArray = function (node, i) {
   if (t.isArrayExpression(node)) {
     return node;
   } else if (t.isIdentifier(node) && node.name === "arguments") {
     return t.callExpression(t.memberExpression(this.addDeclaration("slice"), t.identifier("call")), [node]);
   } else {
-    return t.callExpression(this.addDeclaration("to-array"), [node]);
+    var declarationName = "to-array";
+    var args = [node];
+    if (i) {
+      args.push(t.literal(i));
+      declarationName = "sliced-to-array";
+    }
+    return t.callExpression(this.addDeclaration(declarationName), args);
   }
 };
 

lib/6to5/templates/sliced-to-array.js

@@ -0,0 +1,12 @@
+(function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+      if (i && _arr.length === i) break;
+    }
+    return _arr;
+  }
+});

lib/6to5/transformation/transformers/es6-destructuring.js

@@ -1,6 +1,7 @@
 // TODO: Clean up
 
 var t = require("../../types");
+var _ = require("lodash");
 
 var buildVariableAssign = function (opts, id, init) {
   var op = opts.operator;
@@ -61,9 +62,21 @@ var pushObjectPattern = function (opts, nodes, pattern, parentId) {
 };
 
 var pushArrayPattern = function (opts, nodes, pattern, parentId) {
+  if (!pattern.elements) return;
+
+  var hasSpreadElement = false;
+  for (var i in pattern.elements) {
+    if (t.isSpreadElement(pattern.elements[i])) {
+      hasSpreadElement = true;
+      break;
+    }
+  }
+
+  var toArray = opts.file.toArray(parentId, !hasSpreadElement && pattern.elements.length);
+
   var _parentId = opts.file.generateUidIdentifier("ref", opts.scope);
   nodes.push(t.variableDeclaration("var", [
-    t.variableDeclarator(_parentId, opts.file.toArray(parentId))
+    t.variableDeclarator(_parentId, toArray)
   ]));
   parentId = _parentId;
 

test/fixtures/transformation/es6-constants/destructuring/expected.js

@@ -1,18 +1,29 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 var _ref = [1, 2];
 
-var _ref2 = _toArray(_ref);
+var _ref2 = _slicedToArray(_ref, 2);
 
 var a = _ref2[0];
 var b = _ref2[1];
 var _ref3 = [3, 4];
 
-var _ref4 = _toArray(_ref3);
+var _ref4 = _slicedToArray(_ref3, 2);
 
 var c = _ref4[0];
 var d = _ref4[1];

test/fixtures/transformation/es6-destructuring/array/expected.js

@@ -1,18 +1,29 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 var _ref = ["hello", [", ", "junk"], ["world"]];
 
-var _ref2 = _toArray(_ref);
+var _ref2 = _slicedToArray(_ref, 4);
 
 var a = _ref2[0];
-var _ref3 = _toArray(_ref2[1]);
+var _ref3 = _slicedToArray(_ref2[1], 1);
 
 var b = _ref3[0];
-var _ref4 = _toArray(_ref2[2]);
+var _ref4 = _slicedToArray(_ref2[2], 1);
 
 var c = _ref4[0];
 var d = _ref2[3];

test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js

@@ -1,8 +1,19 @@
 "use strict";
 
 var _temp, _ref;
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
-console.log((_temp = [123], _ref = _toArray(_temp), x = _ref[0], _temp));
+console.log((_temp = [123], _ref = _slicedToArray(_temp, 1), x = _ref[0], _temp));

test/fixtures/transformation/es6-destructuring/assignment-statement/expected.js

@@ -1,12 +1,23 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 var _ref = f();
 
-var _ref2 = _toArray(_ref);
+var _ref2 = _slicedToArray(_ref, 2);
 
 a = _ref2[0];
 b = _ref2[1];

test/fixtures/transformation/es6-destructuring/empty/expected.js

@@ -1,18 +1,29 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 var _ref = ["foo", "hello", [", ", "junk"], ["world"]];
 
-var _ref2 = _toArray(_ref);
+var _ref2 = _slicedToArray(_ref, 5);
 
 var a = _ref2[1];
-var _ref3 = _toArray(_ref2[2]);
+var _ref3 = _slicedToArray(_ref2[2], 1);
 
 var b = _ref3[0];
-var _ref4 = _toArray(_ref2[3]);
+var _ref4 = _slicedToArray(_ref2[3], 1);
 
 var c = _ref4[0];
 var d = _ref2[4];

test/fixtures/transformation/es6-destructuring/for-in/expected.js

@@ -1,11 +1,22 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 for (var _ref in obj) {
-  var _ref2 = _toArray(_ref);
+  var _ref2 = _slicedToArray(_ref, 2);
 
   var name = _ref2[0];
   var value = _ref2[1];

test/fixtures/transformation/es6-destructuring/for-of/expected.js

@@ -1,12 +1,23 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 for (var _iterator = this.test.expectation.registers[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
   var _ref = _step.value;
-  var _ref2 = _toArray(_ref);
+  var _ref2 = _slicedToArray(_ref, 3);
 
   var name = _ref2[0];
   var before = _ref2[1];

test/fixtures/transformation/es6-destructuring/member-expression/expected.js

@@ -1,12 +1,23 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 var _ref = [1, 2];
 
-var _ref2 = _toArray(_ref);
+var _ref2 = _slicedToArray(_ref, 2);
 
 this.foo = _ref2[0];
 this.bar = _ref2[1];

test/fixtures/transformation/es6-destructuring/mixed/expected.js

@@ -1,14 +1,25 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
-var _ref = _toArray(rect.topLeft);
+var _ref = _slicedToArray(rect.topLeft, 2);
 
 var x1 = _ref[0];
 var y1 = _ref[1];
-var _ref2 = _toArray(rect.bottomRight);
+var _ref2 = _slicedToArray(rect.bottomRight, 2);
 
 var x2 = _ref2[0];
 var y2 = _ref2[1];

test/fixtures/transformation/es6-destructuring/parameters/expected.js

@@ -1,7 +1,18 @@
 "use strict";
 
-var _toArray = function (arr) {
-  return Array.isArray(arr) ? arr : Array.from(arr);
+var _slicedToArray = function (arr, i) {
+  if (Array.isArray(arr)) {
+    return arr;
+  } else {
+    var _arr = [];
+    for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) {
+      _arr.push(_step.value);
+
+      if (i && _arr.length === i) break;
+    }
+
+    return _arr;
+  }
 };
 
 function somethingAdvanced(_ref) {
@@ -20,12 +31,12 @@ function unpackObject(_ref2) {
 console.log(unpackObject({ title: "title", author: "author" }));
 
 var unpackArray = function (_ref3, _ref5) {
-  var _ref4 = _toArray(_ref3);
+  var _ref4 = _slicedToArray(_ref3, 3);
 
   var a = _ref4[0];
   var b = _ref4[1];
   var c = _ref4[2];
-  var _ref6 = _toArray(_ref5);
+  var _ref6 = _slicedToArray(_ref5, 3);
 
   var x = _ref6[0];
   var y = _ref6[1];