How to properly hook an action on save in vim

Question

I have a code linter (https://github.com/symplify/easy-coding-standard) that I can run manually from the command line, but which I'd like to run automatically in vim whenever I save a file that I've been working on.

This is what I have so far:

autocmd BufWritePost * execute '! /var/www/sites/mysite/vendor/bin/ecs check %'

Very basic, but kind of works. I'd like to improve it in lots of ways though

1) don't save the file if ecs is unhappy, unless I confirm in some way

2) don't allow vim to quit if I've used :x and there's a problem

3) only run ecs in certain project directories

I've tried googling this problem but didn't come up with much, especially for the first point. Any help appreciated, thank you!

Answer 1

To prevent the saving, you first need to switch from BufWritePost to BufWritePre. But then, the updated file contents are not available yet on the file system, so you'd have to find another way (pipe, temp file) to get them to your linter. In general, this is a non-trivial problem, and I second the recommendation for generic tools like ALE already given in the comments.

If you still want to build a solution yourself:

1. You can abort a write (in BufWritePre) by :throwing an exception (:echoerr might also work).
2. When the buffer isn't persisted, Vim will automatically prevent a non-forceful quit.
3. To limit this to certain directories, the autocmd pattern can be used; instead of *, you can put in file or path globs. But again, this scoping functionality often already is provided by plugins (directly as plugin configuration or indirectly by offering a command to turn off checking for a buffer, which you can then set up via a separate autocmd).