add experimental es7 object spread/rest - closes #200

lib/6to5/file.js

@@ -18,8 +18,16 @@ function File(opts) {
   this.ast          = {};
 }
 
-File.declarations = ["extends", "class-props", "slice", "apply-constructor",
-                     "tagged-template-literal", "interop-require", "to-array"];
+File.declarations = [
+  "extends",
+  "class-props",
+  "apply-constructor",
+  "tagged-template-literal",
+  "interop-require",
+  "to-array",
+  "arguments-to-array",
+  "object-spread"
+];
 
 File.normaliseOptions = function (opts) {
   opts = _.cloneDeep(opts || {});
@@ -73,11 +81,14 @@ File.normaliseOptions = function (opts) {
 File.prototype.toArray = function (node) {
   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 templateName = "to-array";
+  if (t.isIdentifier(node) && node.name === "arguments") {
+    templateName = "arguments-to-array";
+  }
+
+  return t.callExpression(this.addDeclaration(templateName), [node]);
 };
 
 File.prototype.getModuleFormatter = function (type) {

lib/6to5/generation/generators/types.js

@@ -4,7 +4,8 @@ exports.Identifier = function (node) {
   this.push(node.name);
 };
 
-exports.SpreadElement = function (node, print) {
+exports.SpreadElement =
+exports.SpreadProperty = function (node, print) {
   this.push("...");
   print(node.argument);
 };

lib/6to5/generation/node/whitespace.js

@@ -9,6 +9,10 @@ exports.before = {
       }
     },
 
+    SpreadProperty: function (node, parent) {
+      return exports.before.nodes.Property(node, parent);
+    },
+
     SwitchCase: function (node, parent) {
       if (parent.cases[0] === node) {
         return 1;

lib/6to5/transformation/transform.js

@@ -38,6 +38,7 @@ _.each({
   _propertyLiterals:         require("./transformers/_property-literals"),
   computedPropertyNames:     require("./transformers/es6-computed-property-names"),
 
+  objectSpread:              require("./transformers/es7-object-spread"),
   spread:                    require("./transformers/es6-spread"),
   templateLiterals:          require("./transformers/es6-template-literals"),
   propertyMethodAssignment:  require("./transformers/es5-property-method-assignment"),

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

@@ -24,14 +24,33 @@ var push = function (opts, nodes, elem, parentId) {
 };
 
 var pushObjectPattern = function (opts, nodes, pattern, parentId) {
-  _.each(pattern.properties, function (prop) {
-    var pattern2   = prop.value;
-    var patternId2 = t.memberExpression(parentId, prop.key, prop.computed);
+  _.each(pattern.properties, function (prop, i) {
+    if (t.isSpreadProperty(prop)) {
+        // get all the keys that appear in this object before the current spread
+        var keys = [];
+        _.each(pattern.properties, function (prop2, i2) {
+          if (i2 >= i) return false;
+          if (t.isSpreadProperty(prop2)) return;
 
-    if (t.isPattern(pattern2)) {
-      push(opts, nodes, pattern2, patternId2);
+          var key = prop2.key;
+          if (t.isIdentifier(key)) {
+            key = t.literal(prop2.key.name);
+          }
+          keys.push(key);
+        });
+        keys = t.arrayExpression(keys);
+
+        var value = t.callExpression(opts.file.addDeclaration("object-spread"), [parentId, keys]);
+        nodes.push(buildVariableAssign(opts.kind, prop.argument, value));
     } else {
-      nodes.push(buildVariableAssign(opts.kind, pattern2, patternId2));
+      var pattern2   = prop.value;
+      var patternId2 = t.memberExpression(parentId, prop.key, prop.computed);
+
+      if (t.isPattern(pattern2)) {
+        push(opts, nodes, pattern2, patternId2);
+      } else {
+        nodes.push(buildVariableAssign(opts.kind, pattern2, patternId2));
+      }
     }
   });
 };

lib/6to5/transformation/transformers/es7-object-spread.js

@@ -0,0 +1,41 @@
+// https://github.com/sebmarkbage/ecmascript-rest-spread
+
+var t = require("../../types");
+var _ = require("lodash");
+
+exports.ObjectExpression = function (node, parent, file) {
+  var hasSpread = false;
+  _.each(node.properties, function (prop) {
+    if (t.isSpreadProperty(prop)) {
+      hasSpread = true;
+      return false;
+    }
+  });
+  if (!hasSpread) return;
+
+  var args = [];
+  var props = [];
+
+  var push = function () {
+    if (!props.length) return;
+    args.push(t.objectExpression(props));
+    props = [];
+  };
+
+  _.each(node.properties, function (prop) {
+    if (t.isSpreadProperty(prop)) {
+      push();
+      args.push(prop.argument);
+    } else {
+      props.push(prop);
+    }
+  });
+
+  push();
+
+  if (!t.isObjectExpression(args[0])) {
+    args.unshift(t.objectExpression([]));
+  }
+
+  return t.callExpression(t.memberExpression(t.identifier("Object"), t.identifier("assign")), args);
+};

lib/6to5/types/visitor-keys.json

@@ -48,6 +48,7 @@
   "ReturnStatement":           ["argument"],
   "SequenceExpression":        ["expressions"],
   "SpreadElement":             ["argument"],
+  "SpreadProperty":            ["argument"],
   "SwitchCase":                ["test", "consequent"],
   "SwitchStatement":           ["discriminant", "cases"],
   "TaggedTemplateExpression":  ["tag", "quasi"],