Json-Mode / Puppet-Mode unset common functions when installed with use-package

Question

I'm facing a weird issue in my init.el. Installing packages such as json-mode or puppet-mode (from MELPA Stable) with use-package unsets common functions like forward-word or backward-kill-word. The key bindings are unaffected, the function is simply missing (I get Symbol’s function definition is void: nil). This behavior does not happen with all packages (I have dozens of other packages in my init.el which work just fine).

Here is a minimal init.el:

(require 'package)
(setq package-enable-at-startup nil)
(add-to-list 'package-archives '("melpa-stable" . "https://stable.melpa.org/packages/"))
(when (< emacs-major-version 24)
    (add-to-list 'package-archives '("gnu" . "http://elpa.gnu.org/packages/")))
(package-initialize)

(unless (package-installed-p 'use-package)
  (package-refresh-contents)
  (package-install 'use-package)
  )

(eval-when-compile (require 'use-package))
(setq use-package-always-ensure t)                                                                                                                                                                       

(use-package json-mode
  :mode ("\\.json"))


(use-package puppet-mode                                                                                                                                                                                                                                                     
  :mode ("\\.pp"))

Running Emacs with a complete clean .emacs.d (apart from the init file) first installs use-package along with diminish and bind-key and then downloads the two modes json-mode and puppet-mode and adds them to the load-path (as expected).

However, opening a text file test.txt and then running M-f or M-x forward-word returns the error: Symbol’s function definition is void: nil

I'm running Emacs 25.1.1

Is this an issue with these packages, or am I doing something wrong?

Can anyone reproduce this problem?

Answer 1

I still don't understand what's going on internally here (if this is a bug or just my faulty syntax). Nevertheless, I was able to workaround the problem.

Apparently, one cannot use parentheses when having only one argument for :mode (e.g. :mode ("\\.pp")), but has to omit these (i.e. :mode "\\.pp")).

Fix:

-(use-package puppet-mode
-  :mode ("\\.pp"))
+(use-package puppet-mode
+  :mode "\\.pp")


-(use-package json-mode
-  :mode ("\\.json"))
+(use-package json-mode
+  :mode "\\.json")