luacheck: Fails due to cache write race condition

[hunger]

I am trying to use luacheck in pre-commit.ci and get a lot of false positives there.

This is the output I get:

[21 lines ending in ok]
Total: 0 warnings / 0 errors in 21 files
Critical error: Couldn't initialize cache in /tmp/cache/luacheck: Couldn't make directory /tmp/cache/luacheck: File exists

The devs over at pre-commit looked into the issue and came to the conclusion that luacheck is racing with its cache directory creation.

I can reproduce the same thing locally by repeatedly trying this command:

rm -rf ~/.cache/luacheck; PATH=$PWD/opt/lua/bin/:$PATH pre-commit run luacheck --all-files
please report the issue to luacheck

pointing to this code:

luacheck/src/luacheck/fs.lua

Lines 177 to 201 in 81e0835

	local function make_absolute_dirs(dir_path)
	if fs.is_dir(dir_path) then
	return true
	end
	local upper_dir = fs.normalize(fs.join(dir_path, ".."))
	if upper_dir == dir_path then
	return nil, ("Filesystem root %s is not a directory"):format(upper_dir)
	end
	local upper_ok, upper_err = make_absolute_dirs(upper_dir)
	if not upper_ok then
	return nil, upper_err
	end
	local make_ok, make_error = lfs.mkdir(dir_path)
	if not make_ok then
	return nil, ("Couldn't make directory %s: %s"):format(dir_path, make_error)
	end
	return true
	end

This is the issue I raised with pre-commit.ci: pre-commit-ci/issues#114

[alerque]

Yes I see what the issues is ... Unfortunately the bug is even upstream of us, technically the lfs project needs a fix, anything else we can do is just a hack around the missing option there (raised upstream issue here).

In the mean time we can probably fudge and catch this particular error state, check again to see why we we ended up there, then hope for the best and go on. This isn't ideal though and I would suggest part of the problem is luacheck should be allowed to manage it's own threads instead of having them imposed. I'll raise that on the pre-check issue.