README.haskell.md

Haskell Style

Don't stress, just type whatever compiles, then use brittany. Might want to make a git commit before applying inplace rewrite, just in case. Can squash it later.

If you got a nix-shell from the root of treetide-workspace, then formatter tools are already in scope.

brittany --write-mode inplace path/to/source.hs

Note: brittany won't format data decls or typeclasses. Use 4-indent in these if possible. But again, don't stress.

Before running it, you might want to create a commit (to be squashed later) to be safe. After the commit, run

git log --stat HEAD~.. --name-only --format=format:"" | grep '\.hs$' | xargs -n1 brittany --write-mode inplace
git diff

to see the performed changes (available as brittanyPreviousCommit in the nix-shell). If you are brave, go ahead without a commit:

git status --porcelain | grep '^\s*[AM]' | awk '{print $2}' | grep '\.hs$' | xargs -n1 brittany --write-mode inplace

which is available as brittanyChanged in the nix-shell.

Linter checking

Use the handy hlint.

hlint path/to/rootdir/to/check

If it suggests something odd, can add it to .hlint.yaml to ignore. Run hlint path/to/rootdir --default to omit a config that ignores all remaining lint warning types. Merge those with the existing ones.

Interactive lint replace mode

To do interactive inplace suggestion application with hlint, execute:

hlint path/to/rootdir --reformat --reformat-options="-i -s" some/root

which is available as hlintApply in the nix-shell. Note that not all the suggestions can be acted upon by the reformatter. So check hlint output after reformat as well.

Ambiguous suggestions

Hlint likes to suggest eta-reductions, which sometimes make sense, sometimes not (for readability). Use your judgement.

(Extend as needed.)

Running tests with Bazel

Bazel by default caches invocation results, and only reruns if deps changed. But for quickcheck / hedgehog this may not be what we want. In that case use --nocache_test_results flag:

bazel test -c opt treetide/path/to:a_test --test_output=streamed --nocache_test_results