override generator coroutine function length property

use es5 defineProperty
petkaantonov · Jan 23, 2016 · 6bd757e · 6bd757e
1 parent 0dc2861
commit 6bd757e
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Showing 2 changed files with 24 additions and 8 deletions.
diff --git a/src/generators.js b/src/generators.js
@@ -12,6 +12,7 @@ var util = require("./util");
 var errorObj = util.errorObj;
 var tryCatch = util.tryCatch;
 var yieldHandlers = [];
+var defineProperty = require("./es5").defineProperty;
 
 function promiseFromYieldHandler(value, yieldHandlers, traceParent) {
     for (var i = 0; i < yieldHandlers.length; ++i) {
@@ -178,15 +179,25 @@ Promise.coroutine = function (generatorFunction, options) {
     var yieldHandler = Object(options).yieldHandler;
     var PromiseSpawn$ = PromiseSpawn;
     var stack = new Error().stack;
-    return function () {
+
+    function wrap () {
         var generator = generatorFunction.apply(this, arguments);
         var spawn = new PromiseSpawn$(undefined, undefined, yieldHandler,
                                       stack);
         var ret = spawn.promise();
         spawn._generator = generator;
         spawn._promiseFulfilled(undefined);
         return ret;
-    };
+    }
+
+    defineProperty(wrap, "length", {
+      value: generatorFunction.length,
+      writable: false,
+      enumerable: false,
+      configurable: true
+    });
+
+    return wrap;
 };
 
 Promise.coroutine.addYieldHandler = function(fn) {

diff --git a/test/mocha/generator.js b/test/mocha/generator.js
@@ -295,18 +295,23 @@ describe("Promise.coroutine", function() {
             this.goblins = 3;
         }
 
-        MyClass.prototype.spawnGoblins = Promise.coroutine(function* () {
-            this.goblins = yield get(this.goblins+1);
-        });
+        function* gen(increment) {
+            this.goblins = yield get(this.goblins+increment);
+        }
 
+        MyClass.prototype.spawnGoblins = Promise.coroutine(gen);
+
+        specify("generator function's arity should be replicated", function() {
+          assert.equal(MyClass.prototype.spawnGoblins.length, gen.length);
+        });
 
         specify("generator function's receiver should be the instance too", function() {
             var a = new MyClass();
             var b = new MyClass();
 
-            return Promise.join(a.spawnGoblins().then(function(){
-                return a.spawnGoblins()
-            }), b.spawnGoblins()).then(function(){
+            return Promise.join(a.spawnGoblins(1).then(function(){
+                return a.spawnGoblins(1)
+            }), b.spawnGoblins(1)).then(function(){
                 assert.equal(a.goblins, 5);
                 assert.equal(b.goblins, 4);
             });