Make sure all labels we use in rules_haskell are fully qualified

[nmattia]

Last week I got bitten by rules_haskell's assumption that a ./haskell/ directory exists and contains a ghc.BUILD (see #719 (comment)). Most likely this is only the case in the root of this repo. I suspect there are a few similar bugs lurking around.

One way to make sure that we don't make such assumptions is to have tests be run from a different directory.

CC @Profpatsch

[mboes]

You mean from a dependent project. Please update title and description accordingly. I think we should do better than this: detect all hard-coded labels and make sure they are all fully qualified.

[Profpatsch]

detect all hard-coded labels and make sure they are all fully qualified.

What kind of labels are problematic for outside projects?

[mboes]

It's unclear that this still an issue. See bazelbuild/bazel#7130.

[ylecornec]

Indeed, it seems that within the main repository, // at the start of labels should now be equivalent to @rules_haskell//.

[mboes]

OK let's close then.