support array destructuring on iterables - fixes #194

lib/6to5/templates/array-from.js

@@ -0,0 +1 @@
+Array.from(VALUE);

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

@@ -1,5 +1,6 @@
-var t = require("../../types");
-var _ = require("lodash");
+var util = require("../../util");
+var t    = require("../../types");
+var _    = require("lodash");
 
 var buildVariableAssign = function (kind, id, init) {
   if (kind === false) {
@@ -11,45 +12,60 @@ var buildVariableAssign = function (kind, id, init) {
   }
 };
 
-var push = function (kind, nodes, elem, parentId) {
+var push = function (opts, nodes, elem, parentId) {
   if (t.isObjectPattern(elem)) {
-    pushObjectPattern(kind, nodes, elem, parentId);
+    pushObjectPattern(opts, nodes, elem, parentId);
   } else if (t.isArrayPattern(elem)) {
-    pushArrayPattern(kind, nodes, elem, parentId);
+    pushArrayPattern(opts, nodes, elem, parentId);
   } else if (t.isMemberExpression(elem)) {
     nodes.push(buildVariableAssign(false, elem, parentId));
   } else {
-    nodes.push(buildVariableAssign(kind, elem, parentId));
+    nodes.push(buildVariableAssign(opts.kind, elem, parentId));
   }
 };
 
-var pushObjectPattern = function (kind, nodes, pattern, parentId) {
+var pushObjectPattern = function (opts, nodes, pattern, parentId) {
   _.each(pattern.properties, function (prop) {
     var pattern2   = prop.value;
     var patternId2 = t.memberExpression(parentId, prop.key);
 
     if (t.isPattern(pattern2)) {
-      push(kind, nodes, pattern2, patternId2);
+      push(opts, nodes, pattern2, patternId2);
     } else {
-      nodes.push(buildVariableAssign(kind, pattern2, patternId2));
+      nodes.push(buildVariableAssign(opts.kind, pattern2, patternId2));
     }
   });
 };
 
-var pushArrayPattern = function (kind, nodes, pattern, parentId) {
+var pushArrayPattern = function (opts, nodes, pattern, parentId) {
+  var _parentId = t.identifier(opts.file.generateUid("ref", opts.scope));
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(_parentId, util.template("array-from", {
+      VALUE: parentId
+    }))
+  ]));
+  parentId = _parentId;
+
   _.each(pattern.elements, function (elem, i) {
     if (!elem) return;
 
     var newPatternId;
 
     if (t.isSpreadElement(elem)) {
-      newPatternId = t.callExpression(t.memberExpression(parentId, t.identifier("slice")), [t.literal(i)]);
+      newPatternId = util.template("array-from", {
+        VALUE: parentId
+      });
+
+      if (+i > 0) {
+        newPatternId = t.callExpression(t.memberExpression(newPatternId, t.identifier("slice")), [t.literal(i)]);
+      }
+
       elem = elem.argument;
     } else {
       newPatternId = t.memberExpression(parentId, t.literal(i), true);
     }
 
-    push(kind, nodes, elem, newPatternId);
+    push(opts, nodes, elem, newPatternId);
   });
 };
 
@@ -71,7 +87,7 @@ var pushPattern = function (opts) {
     parentId = key;
   }
 
-  push(kind, nodes, pattern, parentId);
+  push(opts, nodes, pattern, parentId);
 };
 
 exports.ForInStatement =
@@ -89,7 +105,11 @@ exports.ForOfStatement = function (node, parent, file, scope) {
 
   var nodes = [];
 
-  push(declar.kind, nodes, pattern, key);
+  push({
+    kind: declar.kind,
+    file: file,
+    scope: scope
+  }, nodes, pattern, key);
 
   t.ensureBlock(node);
 
@@ -141,7 +161,11 @@ exports.ExpressionStatement = function (node, parent, file, scope) {
     t.variableDeclarator(ref, expr.right)
   ]));
 
-  push(false, nodes, expr.left, ref);
+  push({
+    kind: false,
+    file: file,
+    scope: scope
+  }, nodes, expr.left, ref);
 
   return nodes;
 };

lib/6to5/transformation/transformers/spread.js

@@ -1,13 +1,13 @@
-var t = require("../../types");
-var _ = require("lodash");
+var util = require("../../util");
+var t    = require("../../types");
+var _    = require("lodash");
 
 var getSpreadLiteral = function (spread) {
   var literal = spread.argument;
   if (!t.isArrayExpression(literal)) {
-    literal = t.callExpression(
-      t.memberExpression(t.identifier("Array"), t.identifier("from")),
-      [literal]
-    );
+    literal = util.template("array-from", {
+      VALUE: literal
+    });
   }
   return literal;
 };