cabal should lint ~/.cabal/config for compat with selected GHC

[cartazio]

With GHC 7.8, we need shared: True in the cabal config. However, historically shared: False has been explicitly set in people's cabal configs for various reasons.

This is actually a really really recurrent problem as people upgrade to GHC 7.8 and cabal 1.18, and I have to suggest rm ~/.cabal/config ; cabal update as my quick fix for folks.

It would be really nice (and best) if on systems that need dynamic too / shared / etc, if cabal install would holler "shared: False is possibly a problem" or the like.

Maybe there should be a "cabal doctor" or "cabal lint", I just want to not have this gotcha be in my support load.

[kvanbere]

Can confirm that this is kind of an issue with Windows where if you upgrade cabal to a newer one (from the HP versions) a lot of things break, including package lists corrupting, parallel builds not happening and other issues.

Nuking cabal config fixes it, but it'd be nice if automatically chose better defaults or something.

[tibbe]

I think cabal should check for these problems whenever it reads the config file and print a warning.