Introduce treefmt-nix as a universal formatter infra

[benalleng]

This pulls in a commit from #1027 but does not include the ci formatting from there as I believe that we can simply use treefmt-nix for all file types in the ci

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[coveralls]

Pull Request Test Coverage Report for Build 20174624583

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.176%

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Totals
Change from base Build 20173801182:	0.0%
Covered Lines:	9665
Relevant Lines:	11620

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💛 - Coveralls

[spacebear21]

I think any such change should enforce the same formatting rules in CI, otherwise I can see things getting out of sync quickly

[benalleng]

Good point, marking as draft to add this formatting to the CI

[benalleng]

I gave it a college try to add formatting to dart but I kept getting wild diffs in the CI formatter, I don't understand why as dart is notable for having a very strict formatting style. I could never get any formatting to match the CI dart formatter locally

[nothingmuch]

nix code looks good, but i think we should figure out what's wrong with dart formatting before merging

[nothingmuch]

per #1220 (comment), we should add an additional rust-overlay toolchain based on the toolchain.toml rust-bin.fromRustupToolchainFile ./rust-toolchain.toml and format with that instead (it should be equivalent to the rust overlay nightly but if we ever change rust-toolchain.toml then formatting rules will stay in sync)

@spacebear21 is this what you meant here? #1221 (comment)

[spacebear21]

@spacebear21 is this what you meant here? #1221 (comment)

I was just asking for a CI workflow that enforces the formatting rules applied in this PR (when it was posted originally it applied formatting changes but there was no CI validation so I was concerned about eventual regressions).

[benalleng]

Are we even properly linking to our rustfmt.toml file now?

[benalleng]

This commit d906254 I manually made the changes requested by the CI formatter to make it happy but ideally we would have the same options or whatever is causing these changes to be made directly in the treefmt.nix config options.

https://dart.dev/tools/dart-format the dart formatting docs are not really clear on how to add a lot of options

[nothingmuch]

tACK. Also confirmed nix flake check is happy for all commits.