Allow cabal to execute packager-defined commands

[Jookia]

With other build systems like Make you can add custom targets to do different tasks. An example is a 'lang' target to build language files. It'd be nice if custom targets could be added to Cabal.

[byorgey]

I don't think I understand what you're asking for. (I'm not familiar with custom targets in make). Can you give some more specific examples of the kind of thing you would like to be able to do?

[Jookia]

I'd like the ability to add a 'command' to my project somehow, then run 'cabal my_command' which would do what I want.

For instance, say I have a custom command for my project which uses Gettext to create catalogs from my source, then move them to a build directory.

In a hypothetical situation where Cabal has this feature, I'd add the command 'langfiles' to my project.cabal file, which has a name and description for the hypothetical project-specific command section of 'cabal help', and a command 'runhaskell scripts/langfiles.hs' that it'd run when the command is issued.
Then my Haskell file would read the PackageDescription stuff, go through my executables and libraries, scrape the strings from the source file and use Gettext to translate and put them in the appropriate folders in dist/.

Another hypothetical situation would be to have this in my .cabal file:

Custom-Command lint Help: Runs hlint on source code. Task: hlint source

Which would run hlint on my source file, and come up in 'cabal help' like so:

Commands:
install Installs a list of packages.
update Updates list of known packages
list List packages matching a search string.
...

Project Comands:
lint Runs hlint on source code.

I'm aware that Cabal is meant to build packages, but it's the only build system around that's easy to use, and I think it shows evidence that it does non-package-related stuff already with executable documentation, code coverage, tests and benchmarks. This kind of stuff would allow easy extendibility.

[23Skidoo]

Note than you can combine Makefiles with Cabal. The Make build type allows you to delegate the work of actually building the package to make.

[Jookia]

Yes, you can also override Setup.hs and 'hijack' getArgs to do some of your own stuff, but considering Distribution.Simple already has its own command infrastructure it'd be nice to expose this?

[ttuegel]

I renamed this to reflect the similarity to the recent #2349.