util: runtime deprecate util.isFunction

PR-URL: #50488
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Yagiz Nizipli <yagiz.nizipli@sentry.io>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

doc/api/deprecations.md

@@ -1083,6 +1083,9 @@ instead.
 
 <!-- YAML
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/50488
+    description: Runtime deprecation.
   - version:
     - v6.12.0
     - v4.8.6
@@ -1095,7 +1098,7 @@ changes:
     description: Documentation-only deprecation.
 -->
 
-Type: Documentation-only
+Type: Runtime
 
 The [`util.isFunction()`][] API is deprecated.
 

lib/util.js

@@ -437,7 +437,9 @@ module.exports = {
                      'Please use `ObjectPrototypeToString(e) === "[object Error]" ' +
                      '|| e instanceof Error` instead.',
                      'DEP0048'),
-  isFunction: deprecate(isFunction, 'The `util.isFunction API is deprecated.', 'DEP0049'),
+  isFunction: deprecate(isFunction,
+                        'The `util.isFunction` API is deprecated.  Please use `typeof arg === "function"` instead.',
+                        'DEP0049'),
   isPrimitive: deprecate(isPrimitive, 'The `util.isPrimitive API is deprecated.', 'DEP0054'),
   log: deprecate(log, 'The `util.log API is deprecated.', 'DEP0059'),
   promisify,