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About Carlo Sciolla

Carlo Sciolla
An enterprise software engineer by day and Clojurian, meetup organizer, blogger and biker by night, Carlo is an Open Source enthusiast and passionate of every thing software. Currently working as Product Lead at Backbase, he is also the organizer of the Amsterdam Clojurians meetup and the yearly October Amsterdam Clojure conference.

A tale of Emacs, Clojure and pinned packages

It’s like trying to pin down a kangaroo on a trampoline. – Sid Waddel

If you do any clojure[script] development, chances are that you do so through Emacs and CIDER. The experience is generally nothing short of awesome, but every now and then you bump into some quirks. That was the case for me when the latest CIDER came out, mostly due to how I like to keep my Emacs.

tl;dr

CIDER and clj-refactor have incompatible stable releases for which you need to make sure the latter comes from melpa-unstable

Stable vs unstable

I use Clojure to pay the bills, and as such I cannot afford myself to walk too much on the bleeding edge. That’s why I made sure all of my Emacs packages come from a slightly trustworthier stream of stable releases:

(require 'package)

(setq package-archives
      '(("gnu" . "https://elpa.gnu.org/packages/")
        ("melpa" . "https://stable.melpa.org/packages/")
        ("melpa-unstable" . "https://melpa.org/packages/")))

(setq package-archive-priorities
      '(("melpa" . 50)
        ("gnu" . 10)
        ("melpa-unstable" . 0)))

The priorities set on the package archives make sure that released packages (from melpa-stable) will be installed in place of their unstable snapshots if they exist. Ideally I’d love to remove melpa-unstable from my configuration, but there are cases in which that’s some necessary evil to keep. Like the reason why I’m writing this up.

CIDER and clj-refactor and pinning

The latest and gratest CIDER (v0.17.0) earlier in May 2018, while the latest clj-refactor release is pretty ancient, dating back to June 2017. The two packages are now not compatible, and if you installed both in your Emacs your REPL will fail to start. This has been reported many, many, many times in the clj-refactor issue tracker, but Java 9 compatibility is holding back any new releases of clj-refactor, which means we might be waiting quite some time before we can have a stable clojure IDE including refactorings. We need to fiddle around ourselves:

;; manual package pinning:
(add-to-list 'package-pinned-packages '(clj-refactor . "melpa-unstable") t)

;; or if you're using `use-package' to install packages:
(use-package clj-refactor
  :ensure t
  :pin "melpa-unstable"
  ...)

That’s it. You can now safely upgrade your packages and enjoy your clojure IDE once again.

As duly noted by dantheobserver in the comments, use-package itself is pending a stable release for some time now. As such, you only have one way to properly pin it, similarly to the first option above:

(add-to-list 'package-pinned-packages '(use-package . "melpa-unstable") t)

Happy hacking!

Published on Java Code Geeks with permission by Carlo Sciolla, partner at our JCG program. See the original article here: A tale of Emacs, Clojure and pinned packages

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