Relocatable data-files: support

[lukexi]

I have some packages that require some accompanying data to be placed alongside any executables that depend on them; in a few cases that's some closed-source DLLs, and in another it's some shader files. I could use file-embed as a workaround for the shaders, but the DLLs aren't as straightforward.

cabal-install has the ability to specify where the data-files: of a package are placed via --datadir and --datasubdir, which I think would solve this nicely alongside the existing --local-bin-dir option?

(I haven't needed this until I switched to Stack, but I assume cabal-install's --datadir flag works alongside the Paths_foo module system to enable use of getDataFileName regardless of installation destination, for the shader example case)

[borsboom]

@lukexi, will #848 do what you need? If not, is there a way that proposal could be extended to support what you need?

[borsboom]

For lack of feedback, closing as duplicate of #848.

[lukexi]

Whoops, sorry I missed this!

I think #848 will do the trick — I'll explain exactly what I'm hoping for just in case and you can close again if #848 subsumes it : )

Say I have a dependency tree like this:

foo
|
bar baz
|    |
\   /
 bat

bat defines an executable, and all of the projects have data-files in their .cabal.

When I run stack install --prefix releasedir, I want to have all of foo, bar, baz and bat's data-files along with bat's executable installed into releasedir, and for Paths_Foo, Paths_Bar, and Paths_baz to be configured so that bat's executable can load data from them at runtime.

Hope that makes sense : )

[borsboom]

Pretty sure #848 will cover this case. I'll reference your case over there to make sure.