Providing a smooth default user experience

[Simon Hengel]

> Recently, I had to add a MIN_VERSION macro to my code because of the
> old-time / time change in directory, but couldn't test the library in
> ghci because the macro was not defined.
> 
> I discovered that configuring ghci with
> 
>   :set -optP-include -optPdist/build/autogen/cabal_macros.h
> 
> tells ghci about the macro, but I find this even more cumbersome than
> dist/build/<executable>/<executable>.
> 
> So, if I'm not missing something, it may also be comfortable to add a
> 
> cabal ghci
> 
> command which tells ghci about cabal's configuration.

You can put the required options in a .ghci file in you project root.  I
use [3] as a starting point for new projects, [2] and [3] are real world
examples.

`cabal ghci` could still be useful, but I think a general solution is
not trivial.  It would probably need to accept qualified targets, e.g.
`ghci test:properties` to start ghci in a way suitable for a test-suite
with the name "properties".

Moreover, it would be awesome if it would regenerate generated source
files on :reload.  I'm not sure if this is feasible without changes to
GHCi, but a custom macro, e.g.

    :cabal-reload

could still work.

Cheers,
Simon

[1] http://hpaste.org/77144
[2] https://github.com/ghc/haddock/blob/ghc-7.6/.ghci
[3] https://github.com/sol/doctest-haskell/blob/master/.ghci