Specify intra-package target (like 'cabal build COMPONENTS')

[chreekat]

This may fit in with the talk of building test suites somewhat independently of a project itself.

Suggest keeping stack build TARGET syntax, just making TARGET more flexible — So I can do any of

stack build .              # everything
stack build Snowdrift      # Snowdrift package
stack build exe:Snowdrift  # Snowdrift component

May be slightly ambiguous, but I doubt that would be a problem very often.

[snoyberg]

Worth exploring, but we may be constrained by what Cabal allows us to do here. If anyone has experience with Cabal on this front, please speak up.

[bitemyapp]

+1 if it doesn't get ornate or complicated.

I don't have a lot to contribute re: Cabal. I've gotten away with specifying specific suites/stanzas by name, cabal test, and cabal build without needing much else so far.

[snoyberg]

Gah, I can't believe I never realized that you can just pass in the components to runghc Setup.hs build. OK, this should be trivial to implement. I think I'd prefer to reverse the order of your TARGET syntax to be PACKAGE:COMPONENT, which would be symmetrical with the flag syntax (which is PACKAGE:FLAG).

[chreekat]

Fwiw, in my example "exe:Snowdrift" is the component (not 'component:package' — just 'component'). If we tacked package on to that, it would be Snowdrift:exe:Snowdrift. That's why I hoped it wouldn't be hard to add a heuristic to figure out which package a particular component belonged to, so one could simply specify a component by itself.

Of course, Snowdrift:exe:Snowdrift would be an acceptable first pass.

[snoyberg]

Is the exe necessary to disambiguate? I thought there was a requirement in cabal files that you couldn't give a test suite and executable the same name.

[chreekat]

In this case the choices are exe:Snowdrift and lib:Snowdrift.

[snoyberg]

@chreekat This is now implemented. This does require prefixing the component name with the package name (doing otherwise would have led to ambiguities with the current syntax). This, for example, works:

stack build stack:lib:stack

Can you try it out?