Cabal plugins

On Fri, Oct 21, 2011 at 3:49 PM, Jason Dagit wrote:

On Fri, Oct 21, 2011 at 1:29 PM, Brent Yorgey wrote:

...

Hi everyone,

I'm working on some improvements to 'cabal init', the biggest of which is looking at imports in source files to guess an initial list of dependencies to populate the 'Build-depends:' field.  I wanted to get some feedback on a design decision: what to do when we find multiple packages providing the same module?

While cabal init is something I use, I would prefer to have a separate tool for calculating my build-depends field.  Something that could suggest things for an existing cabal project, ideally.  Then I could run that regularly during development to help me determine what my build-deps should be and cabal init could suggest I run it (or run it for me).

While I'm suggesting features I would like, wouldn't it be great if cabal used the plugin RFC that Simon came up with? http://www.mail-archive.com/haskell-cafe@haskell.org/msg92770.html

I think that interface is a great way to unify the tools that have sprung up around cabal such as cabal-dev and cab.

One thing that will be hard for plugins is that there's no way to get at the package hooks without entering through Setup.main. This means that if your plugin wants to, say, call haddock with slightly tweaked arguments, you might miss something important that the standard 'cabal haddock' would have gotten because it runs the user hooks. (This concern only applies if your plugin is using the Cabal library to open up the package description and root around and do things). There's probably still a lot you can do, though - something like 'cabal-dev' could be entirely written as a plugin (and I guess it would be out-of-the-box: 'cabal dev configure' would 'just work' under this proposal, although the help text would need to change). Antoine