add formatter schema

[zimbatm]

This is needed for flakes that want to support nix fmt.

Right now it's missing some testing as I didn't find a test framework for it.

Needed by numtide/treefmt#169

[roberth]

Seems to work after suggestions and looks alright.

Right now it's missing some testing as I didn't find a test framework for it.

Yeah the testing situation is kinda bad because I don't want to pollute the repo with test dependencies and such. People complain about those, even in other repos that aren't low level like this one. Not sure if I should wait for something like NixOS/nix#6124

[zimbatm]

Yeah the testing situation is kinda bad because I don't want to pollute the repo with test dependencies and such. People complain about those, even in other repos that aren't low level like this one. Not sure if I should wait for something like NixOS/nix#6124

Yeah, I know what you mean. One workaround would be to add a tests/flake.nix that refers back to the root flake. nix run ./tests#.?

[roberth]

One workaround would be to add a tests/flake.nix that refers back to the root flake. nix run ./tests#.?

Yeah, I'm doing something similar in the dev directory, though that's a very unusual not-quite-flake because you can't reference up (../), at least not when I wrote that solution.

[zimbatm]

Oh well :) I think this is ready. I switched the upstream PR to this branch, and it's working as intended.

[roberth]

bors r+

[bors]

Build succeeded:

• ci/hercules/evaluation
• ci/hercules/onPush/default