Incremental formatting?

[michalrus]

Maybe we could have incremental formatting? I.e. when run for a directory, reformatting only the files with updated times (since last formatting)?

Here’s an example of how to do that with a plain old Makefile:

https://github.com/michalrus/kornel/blob/5c99123afcbb04b555570093c0d5fad0cf7edf23/Makefile#L33-L41

So for each %.hs file, it touches an empty dist/autoformat/%.hs_autoformat. And reformats only these files for which %.hs has time fresher than dist/autoformat/%.hs_autoformat.

Something like that would be very cool. ♥

[danstiner]

Neat approach, I assume the problem is how slow it is to run a format (it is indeed quite slow). Several things could be done to speed it up some, but I agree the best solution is to only run it on the files that actually might need it.

I would be open to including such logic in this tool if you'd like to send a PR :) but I'm not writing much Haskell lately so I probably won't be getting around to it personally anytime soon. I actually think such logic would be re-usable by other tools and would be great as a separate library.

Currently I enjoy having some plugins set up in my editor to run stylish-haskell on save and show suggestions from hlint and then manually run hfmt before check-in. For the Atom editor see ide-haskell.