fix: callbackify resulting function should have one more argument

Author: erossignon

test/browser/callbackify.js

@@ -167,3 +167,18 @@ test('util.callbackify non-function inputs throw', function (t) {
   });
   t.end();
 });
+
+test('util.callbackify resulting function should have one more argument', function (t) {
+  // Test that resulting function should have one more argument
+  [
+    function() { },
+    function(a) { },
+    function(a, b) { }
+  ].forEach(function (fct) {
+
+    var callbackified = callbackify(fct);
+    t.strictEqual(callbackified.length, fct.length + 1, "callbackified function should have one more argument");
+  });
+  t.end();
+});
+

test/node/callbackify.js

@@ -193,3 +193,29 @@ if (false) {
 if (require('is-async-supported')()) {
   require('./callbackify-async');
 }
+
+(function callbackify_resulting_function_should_have_one_more_argument() {
+
+  var nodeJSVersion = parseInt(process.version.substring(1,3),10);
+
+  console.log("Testing callbackify resulting function should have one more argument")
+  var original_callbackify = require('util').callbackify;
+  // Test that resulting function should have one more argument
+  [
+    function(){ },
+    function(a){ }, 
+    function(a, b) { }
+  ].forEach(function (fct) {
+
+    var node_callbackified = original_callbackify(fct);
+    var browser_callbackified = callbackify(fct);
+
+    if (nodeJSVersion >= 12 && node_callbackified.length !== fct.length + 1) {
+      // this behavior is only true with node 12 and above, where the bug was fixed
+      throw new Error("callbackified function should have one more argument");
+    }
+    if (browser_callbackified.length !== node_callbackified.length) {
+      throw new Error("callbackified function should have one more argument, like in node");
+    }
+  });
+})();

util.js

@@ -708,8 +708,9 @@ function callbackify(original) {
   }
 
   Object.setPrototypeOf(callbackified, Object.getPrototypeOf(original));
-  Object.defineProperties(callbackified,
-                          getOwnPropertyDescriptors(original));
+  const desc = getOwnPropertyDescriptors(original);
+  desc.length.value += 1;
+  Object.defineProperties(callbackified, desc);
   return callbackified;
 }
 exports.callbackify = callbackify;