Pretty ?λ character caused reader error in clojure-mode.el

[egbulmer]

Installed this package for the first time using M-x el-get-install cider and I see this error when I try to edit a .clj file (invalid-read-syntax "?"). I believe this is because the file is not in a unicode format and so it does not understand the lambda character. This is what I see

(defconst clojure--prettify-symbols-alist
  '(("fn"  . ?λ)))

I need to manually change it to ?λ and then save the buffer as utf-8 to resolve the issue. I'm running Emacs 24.3 on a Windows machine. Looks like the file is encoded correctly on github. I guess this means the encoding got messed up somewhere along the lines. Any thoughts on how this could happen?

[bbatsov]

I'm puzzled; other modes in Emacs have unicode characters in their code (like lisp-mode). You can try putting something like this in your config:

 (set-language-environment 'utf-8)
 (setq locale-coding-system 'utf-8)
 (set-default-coding-systems 'utf-8)
 (set-terminal-coding-system 'utf-8)

[mbsmith]

I was also having this issue, and your suggestion fixed the issue for me.

[tanzoniteblack]

@bbatsov rather than assuming/hoping that everyone has this set correctly, we should probably add ;; coding: utf-8 to the Local Variables.

Can someone who's experiencing this issue try adding the line ;; coding: utf-8 below ;; Local Variables: at the bottom of clojure-mode.el file, reload the file (probably best to just restart emacs), and see if this fixes the issue?

;; Local Variables:
;; coding: utf-8
;; byte-compile-warnings: (not cl-functions)
;; indent-tabs-mode: nil
;; End:

[bbatsov]

@tanzoniteblack Perhaps... I haven't done so because I was under the impression utf-8 was the default encoding in 24.x. There are unicode chars in the source code of 24.4 in files without explicit encoding (like lisp-mode.el), so I wonder if utf-8 was made default in 24.4.

[root42]

I think this should be a more safe alternative to the workaround:

(prefer-coding-system 'utf-8)

Forcing everything to be utf-8 might break some things that are not utf-8.

[egbulmer]

Just tested this fix with a fresh install. Works like a charm, thank-you!