util: support classes in util.deprecate()

Classes cannot be instantiated without new, but util.deprecate()
uses Function.prototype.apply(). This commit uses new.target to
detect constructor calls, allowing classes to be deprecated.

PR-URL: https://github.com/nodejs/node/pull/7690
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <mic.besace@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/internal/util.js b/lib/internal/util.js
index e3d9a66b3b..073879d9e9 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -60,9 +60,18 @@ exports._deprecate = function(fn, msg) {
   var warned = false;
   function deprecated() {
     warned = exports.printDeprecationMessage(msg, warned, deprecated);
+    if (new.target) {
+      return Reflect.construct(fn, arguments, new.target);
+    }
     return fn.apply(this, arguments);
   }
 
+  // The wrapper will keep the same prototype as fn to maintain prototype chain
+  Object.setPrototypeOf(deprecated, fn);
+  if (fn.prototype) {
+    Object.setPrototypeOf(deprecated.prototype, fn.prototype);
+  }
+
   return deprecated;
 };