Wrong json-mode formatter chosen when specified in dir-locals file

[daut]

I'm trying to specify different formatters for three different modes in .dir-locals.el file. Here's how the file looks like.

((js-mode . ((apheleia-formatter . eslint)))
 (json-mode . ((apheleia-formatter . prettier-json)))
 (web-mode . ((apheleia-formatter . eslint))))

js and web mode files are correctly using eslint formatter, but json-mode incorrectly uses eslint as well. When I delete the first line from the above dir-locals file json-mode correctly has prettier-json set in the apheleia-formatter variable.

I'm suspecting this is caused by the fact that javascript-mode is json-mode's parent, but don't have an idea how to fix it. Are there any ways around this?

[raxod502]

Hm. When I create that .dir-locals.el file and open a JSON file in the same directory, the value of the variable apheleia-formatter in that buffer is prettier-json.

What version of Emacs is this? I am testing with 28.1.

[daut]

I'm on 29.1.

GNU Emacs 29.1 (build 1, aarch64-apple-darwin23.1.0, NS appkit-2487.20 Version 14.1.1 (Build 23B81)) of 2023-11-19

[raxod502]

Okay, I can reproduce this - make docker VERSION=29 CMD="make fmt-emacs" and then create the described files.

[raxod502]

Oh, okay.

The problem is in Emacs 29 there is a builtin json-mode, but it's not called json-mode, it's called js-json-mode.

Change your .dir-locals.el as:

((js-json-mode . ((apheleia-formatter . eslint)))
 (json-mode . ((apheleia-formatter . prettier-json)))
 (web-mode . ((apheleia-formatter . eslint))))

(or include entries for both mode names if you want to cover both versions).

Meanwhile in Emacs 28 my json-mode is provided by an external package and is really called json-mode.

[daut]

OK, thanks!

I was actually using json-mode too for .json files. Switching to js-json-mode does solve the issue.