fix no RHS in class properties causing undefined to be used instead of a noop - fixes #1396

src/babel/transformation/templates/helper-create-decorated-class.js

@@ -24,7 +24,7 @@
           }
         }
 
-        if (descriptor.initializer) {
+        if (descriptor.initializer !== undefined) {
           initializers[key] = descriptor;
           continue;
         }

src/babel/transformation/templates/helper-create-decorated-object.js

@@ -26,9 +26,10 @@
       }
     }
 
-    descriptor.value = descriptor.initializer.call(target);
-
-    Object.defineProperty(target, key, descriptor);
+    if (descriptor.initializer) {
+      descriptor.value = descriptor.initializer.call(target);
+      Object.defineProperty(target, key, descriptor);
+    }
   }
 
   return target;

src/babel/transformation/templates/helper-define-decorated-property-descriptor.js

@@ -6,6 +6,7 @@
   for (var _key in _descriptor) descriptor[_key] = _descriptor[_key];
 
   // initialize it
+  if (!descriptor.initializer) return;
   descriptor.value = descriptor.initializer.call(target);
 
   Object.defineProperty(target, key, descriptor);

src/babel/transformation/transformers/es6/classes.js

@@ -550,8 +550,12 @@ class ClassTransformer {
 
     if (node.decorators) {
       var body = [];
-      if (node.value) body.push(t.returnStatement(node.value));
-      node.value = t.functionExpression(null, [], t.blockStatement(body));
+      if (node.value) {
+        body.push(t.returnStatement(node.value));
+        node.value = t.functionExpression(null, [], t.blockStatement(body));
+      } else {
+        node.value = t.literal(null);
+      }
       this.pushToMap(node, true, "initializer");
 
       var initializers;
@@ -575,7 +579,7 @@ class ClassTransformer {
         ])
       ));
     } else {
-      node.value = node.value || t.identifier("undefined");
+      if (!node.value && !node.decorators) return;
 
       if (node.static) {
         // can just be added to the static map

test/core/fixtures/transformation/es7.class-properties/instance-undefined/expected.js

@@ -2,5 +2,4 @@
 
 var Foo = function Foo() {
   babelHelpers.classCallCheck(this, Foo);
-  this.bar = undefined;
-};
+};

test/core/fixtures/transformation/es7.class-properties/static-undefined/exec.js

@@ -2,5 +2,5 @@ class Foo {
   static num;
 }
 
-assert.equal("num" in Foo, true);
+assert.equal("num" in Foo, false);
 assert.equal(Foo.num, undefined);

test/core/fixtures/transformation/es7.class-properties/static-undefined/expected.js

@@ -1,14 +1,5 @@
 "use strict";
 
-var Foo = (function () {
-  function Foo() {
-    babelHelpers.classCallCheck(this, Foo);
-  }
-
-  babelHelpers.createClass(Foo, null, [{
-    key: "bar",
-    value: undefined,
-    enumerable: true
-  }]);
-  return Foo;
-})();
+var Foo = function Foo() {
+  babelHelpers.classCallCheck(this, Foo);
+};

test/core/fixtures/transformation/es7.decorators/class-no-init-instance-props/expected.js

@@ -11,8 +11,8 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, [{
     key: "foo",
     decorators: [bar],
-    initializer: function () {},
+    initializer: null,
     enumerable: true
   }], null, _instanceInitializers);
   return Foo;
-})();
+})();

test/core/fixtures/transformation/es7.decorators/class-no-init-static-props/expected.js

@@ -10,7 +10,7 @@ var Foo = (function () {
   babelHelpers.createDecoratedClass(Foo, null, [{
     key: "foo",
     decorators: [bar],
-    initializer: function () {},
+    initializer: null,
     enumerable: true
   }], null, _staticInitializers);
   babelHelpers.defineDecoratedPropertyDescriptor(Foo, "foo", _staticInitializers);