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, 19 insertions, 0 deletions

diff --git a/test/fixtures/deprecated-userland-subclass.js b/test/fixtures/deprecated-userland-subclass.js
new file mode 100644
index 0000000000..2df374ad7d
--- /dev/null
+++ b/test/fixtures/deprecated-userland-subclass.js
@@ -0,0 +1,19 @@
+const util = require('util');
+const assert = require('assert');
+
+class deprecatedClass {
+}
+
+const deprecated = util.deprecate(deprecatedClass, 'deprecatedClass is deprecated.');
+
+class subclass extends deprecated {
+  constructor() {
+    super();
+  }
+}
+
+const instance = new subclass();
+
+assert(instance instanceof subclass);
+assert(instance instanceof deprecated);
+assert(instance instanceof deprecatedClass);