add support for generator comprehensions - fixes #149

FEATURES.md

@@ -95,6 +95,11 @@ for (var i of [1, 2, 3]) {
 ```javascript
 ```
 
+## Generator comprehension
+
+```javascript
+```
+
 ## Modules
 
 ```javascript

lib/6to5/generation/generator.js

@@ -53,16 +53,16 @@ CodeGenerator.normaliseOptions = function (opts) {
 };
 
 CodeGenerator.generators = {
-  arrayComprehensions: require("./generators/array-comprehensions"),
-  templateLiterals:    require("./generators/template-literals"),
-  expressions:         require("./generators/expressions"),
-  statements:          require("./generators/statements"),
-  classes:             require("./generators/classes"),
-  methods:             require("./generators/methods"),
-  modules:             require("./generators/modules"),
-  types:               require("./generators/types"),
-  base:                require("./generators/base"),
-  jsx:                 require("./generators/jsx")
+  templateLiterals: require("./generators/template-literals"),
+  comprehensions:   require("./generators/comprehensions"),
+  expressions:      require("./generators/expressions"),
+  statements:       require("./generators/statements"),
+  classes:          require("./generators/classes"),
+  methods:          require("./generators/methods"),
+  modules:          require("./generators/modules"),
+  types:            require("./generators/types"),
+  base:             require("./generators/base"),
+  jsx:              require("./generators/jsx")
 };
 
 _.each(CodeGenerator.generators, function (generator) {
@@ -76,7 +76,6 @@ CodeGenerator.prototype.generate = function () {
 
   return {
     map:  this.map.get(),
-    ast:  ast,
     code: this.buffer.get()
   };
 };

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

@@ -8,7 +8,8 @@ exports.ComprehensionBlock = function (node, print) {
 };
 
 exports.ComprehensionExpression = function (node, print) {
-  this.push("[");
+  this.push(node.generator ? "(" : "[");
+
   print.join(node.blocks, { separator: " " });
   this.space();
 
@@ -21,5 +22,6 @@ exports.ComprehensionExpression = function (node, print) {
   }
 
   print(node.body);
-  this.push("]");
+
+  this.push(node.generator ? ")" : "]");
 };

lib/6to5/register.js

@@ -36,6 +36,7 @@ var blacklistTest = function (transformer, code) {
 };
 
 blacklistTest("arrayComprehension", "var foo = [for (foo of bar) foo * foo];");
+//blacklistTest("generatorComprehension", "");
 blacklistTest("arrowFunctions", "var foo = x => x * x;");
 blacklistTest("classes", "class Foo {}");
 blacklistTest("computedPropertyNames", "var foo = { [foo]: bar };");

lib/6to5/transformation/transform.js

@@ -31,6 +31,7 @@ _.each({
   propertyNameShorthand:    require("./transformers/property-name-shorthand"),
   constants:                require("./transformers/constants"),
   arrayComprehension:       require("./transformers/array-comprehension"),
+  generatorComprehension:   require("./transformers/generator-comprehension"),
   arrowFunctions:           require("./transformers/arrow-functions"),
   classes:                  require("./transformers/classes"),
 

lib/6to5/transformation/transformer.js

@@ -15,6 +15,7 @@ Transformer.normalise = function (transformer) {
   }
 
   _.each(transformer, function (fns, type) {
+    if (type[0] === "_") return;
     if (_.isFunction(fns)) fns = { enter: fns };
     transformer[type] = fns;
   });

lib/6to5/transformation/transformers/array-comprehension.js

@@ -37,39 +37,42 @@ var multiple = function (node, file) {
 
   var returnStatement = body.pop();
 
-  var build = function () {
-    var self = node.blocks.shift();
-    if (!self) return;
-
-    var child = build();
-    if (!child) {
-      // last item
-
-      child = util.template("array-push", {
-        STATEMENT: node.body,
-        KEY:       uid
-      }, true);
-
-      // add a filter as this is our final stop
-      if (node.filter) {
-        child = t.ifStatement(node.filter, t.blockStatement([child]));
-      }
-    }
-
-    return t.forOfStatement(
-      t.variableDeclaration("var", [t.variableDeclarator(self.left)]),
-      self.right,
-      t.blockStatement([child])
-    );
-  };
-
-  body.push(build());
+  body.push(exports._build(node, function () {
+    return util.template("array-push", {
+      STATEMENT: node.body,
+      KEY:       uid
+    }, true);
+  }));
   body.push(returnStatement);
 
   return container;
 };
 
+exports._build = function (node, buildBody) {
+  var self = node.blocks.shift();
+  if (!self) return;
+
+  var child = exports._build(node, buildBody);
+  if (!child) {
+    // last item
+    child = buildBody();
+
+    // add a filter as this is our final stop
+    if (node.filter) {
+      child = t.ifStatement(node.filter, t.blockStatement([child]));
+    }
+  }
+
+  return t.forOfStatement(
+    t.variableDeclaration("var", [t.variableDeclarator(self.left)]),
+    self.right,
+    t.blockStatement([child])
+  );
+};
+
 exports.ComprehensionExpression = function (node, parent, file) {
+  if (node.generator) return;
+
   if (node.blocks.length === 1 && t.isArrayExpression(node.blocks[0].right)) {
     return singleArrayExpression(node);
   } else {

test/fixtures/transformation/generator-comprehension/simple/exec.js

@@ -0,0 +1,6 @@
+var nums = [1, 2, 3, 4, 5, 6];
+var multiples = (for (i of nums) if (i % 2) i * i);
+assert.equal(multiples.next().value, 1);
+assert.equal(multiples.next().value, 9);
+assert.equal(multiples.next().value, 25);
+assert.ok(multiples.next().done);