Lint code in PRs and when committing to master

[tarleb]

This adds a new GitHub Actions workflow which checks the code with HLint for all PRs and commits to master. Most linter annotations in the code are resolved; the remaining warnings are disabled via configs.

[tarleb]

This is a bit of an experiment. I have generally had good experiences using linters in this way in other projects. But there is always the danger that it gets in the way more than it helps.

[jgm]

Yeah, I'm not sure. I normally don't always apply hlint's suggestions, so I'm not sure I'd want to make it a requirement for commits.

Sometimes I find that some parentheses that aren't strictly necessary are helpful to make the code more readable by humans, for example.

[tarleb]

That's very true. The PR disables multiple hints because they would have made things worse (IMHO).

I am using automatic linting checks in hslua; so far the experience has been good. However, my feeling is that unnecessary warnings happen more often than in other languages. Maybe this would get annoying quickly when used in a project of pandoc's size.

I haven't tried it yet, but maybe the hint-man bot could be a good alternative.

[mb21]

Not sure if this has already been discussed, but we could also go full blown with https://github.com/tweag/ormolu

[tarleb]

Ormolu and similar tools are great in a company environment IMHO. I wouldn't want to use them in pandoc though.

[jgm]

Let's try it. If the automatic lint action gets to be a pain, we can disable it. But even if we do, these changes to hlint config and to the code are useful.

[jgm]

@tarleb I'm confused about how this works! (Background: I was trying to add a matching lint step to my pre-push procedure.)
Can you explain it?
The main action is

curl -sSL "${hlint_script}" | sh -s .

where hlint_script = https://raw.github.com/ndmitchell/hlint/master/misc/run.sh.
Now if I got to that URL, I see

#!/bin/sh
curl -sSL https://raw.github.com/ndmitchell/neil/master/misc/run.sh | sh -s -- hlint $*

So, we download a script and run it, and the script says to download itself and pipe itself to hlint? What is going on here?
I tried doing hlint . in the pandoc source directory, but I got many more warnings than the CI gives.

[tarleb]

I took that line from the hlint docs' CI section. Following all URL redirects and indirections, I end up at https://raw.githubusercontent.com/ndmitchell/neil/master/misc/run.sh, which downloads hlint from its GitHub release page. This does seem overly convoluted.

I tried doing hlint . in the pandoc source directory, but I got many more warnings than the CI gives.

That's weird, I'm not getting any warnings right now. I don't know what's going on there.

[tarleb]

FWIW, I'm running hlint 3.2.

[tarleb]

My pre-commit hook is

#!/bin/sh
git diff --cached --name-only | grep '.hs$' | xargs hlint --hint .hlint.yaml

[jgm]

I've got an older hlint, that may be the issue.

[jgm]

Upgraded hlint. That did it. Thanks for the pre-commit hook.