chore: add treefmt formatting (nix fmt + pre-commit + CI check)#5
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Wire treefmt via treefmt-nix: nixfmt, dhall format, purs-tidy (.tidyrc.json) and LuaFormatter for the FFI (.lua-format, kept over StyLua because it preserves the parentheses pslua's parser needs). `nix fmt` formats; the dev shell installs a content-based pre-commit hook and CI runs `nix fmt && git diff --exit-code` (content-based, since the in-place formatters bump mtime and would trip treefmt --fail-on-change). Lua lines budget 130 cols, matching the raised `luacheck --max-line-length`. This fork has no hand-written FFI, so luacheck stays over the generated dist/.
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Pull request overview
This PR adds a repo-wide formatting setup using treefmt-nix, wiring it into the flake so nix fmt works locally, a formatting check is exposed via flake checks, CI enforces formatting, and the dev shell installs a pre-commit hook to block unformatted commits.
Changes:
- Add
treefmt.nixand wiretreefmt-nixintoflake.nix(formatter +checks.formatting) with a dev-shell pre-commit hook. - Introduce formatter configs for PureScript and Lua (
.tidyrc.json,.lua-format) and ensure they’re not ignored by git. - Update CI and contributor docs to include formatting and updated luacheck settings.
Reviewed changes
Copilot reviewed 6 out of 8 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| treefmt.nix | Defines treefmt formatters (nix/dhall/purs-tidy/lua-format) and global excludes. |
| flake.nix | Adds treefmt-nix input, exposes formatter/checks.formatting, and installs a pre-commit hook in devShell. |
| flake.lock | Locks the new treefmt-nix dependency. |
| AGENTS.md | Documents formatting (nix fmt) and updates luacheck line-length guidance. |
| .tidyrc.json | Adds purs-tidy formatting configuration. |
| .lua-format | Adds LuaFormatter configuration. |
| .gitignore | Unignores the new formatter config dotfiles so they can be committed. |
| .github/workflows/ci.yml | Adds a nix fmt && git diff --exit-code formatting check step and updates luacheck flags. |
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Roll the ecosystem formatting setup (ADR 0007, piloted in purescript-lua/purescript-lua-effect#6) onto this fork.
Tooling. Copies
treefmt.nix/.tidyrc.json/.lua-formatand wires treefmt-nix into the flake:nix fmtformats,checks.formattingis exposed, the dev shell installs a content-based pre-commit hook, and CI gains a format-check step. The check is content-based (nix fmt && git diff --exit-code) rather thantreefmt --ci, since the in-place formatters bump mtime even when content is unchanged.Fork specifics. No hand-written FFI here, so
luacheckstays over the generateddist/; the--max-line-lengthis raised to 130 to match the Lua budget. The.purswas already purs-tidy clean, so the diff is just the tooling wiring. Verified locally: build +luacheck --max-line-length 130green.