Path to build artifacts changes depending on the build-type

[23Skidoo]

For example, if I have a package foo with an executable exe, with build-type: Simple the executable will be under

dist-newstyle/build/x86_64-linux/ghc-8.2.1/foo-1.0/c/exe/build/exe/exe

But if I change the build type to Custom, it will be under

dist-newstyle/build/x86_64-linux/ghc-8.2.1/foo-1.0/build/exe/exe

This is with Cabal 2.0.

/cc @ezyang

[ezyang]

Unfortunately, this is expected behavior. In particular, it has less to do with Custom, and more to do with whether or not we support per-component builds; per-component builds have a different directory layout.

Is there a broader context where this is a problem?

[23Skidoo]

It's just a bit confusing and annoying. For example, if a user switches a build-type: Simple project to build-type: Custom, it may take them a while to realise that the directory layout is now different. Plus if those paths are hardcoded somewhere (e.g. in CI conf, scripts or an external build system) they now have to be changed.

[ezyang]

So, there are some workarounds available to us. For example, after running an old-style setup script, we could copy / otherwise move binaries so that they show up in the locations people "expect". This might be a bit too magical, but it would "solve" the problem, to a certain extent.

[ivan-m]

Is there support to programmatically discover where these paths are? If that's promoted, then scripts can refer to those locations rather than trying to discover them themselves.

[gbaz]

Agreed -- a flag to builds that output paths to executable artifacts as a result would be welcome in general.

[hvr]

@ivan-m for new-build, you can use http://hackage.haskell.org/package/cabal-plan to programmatically query the paths for build targets.