Implement support for Cabal CPP pragmas

[lykahb]

When a file has a pragma with Cabal macros like

#if MIN_VERSION_template_haskell(2, 7, 0)

it would not loaded by the inferior haskell process because of

error: missing binary operator before token "("
phase `C pre-processor' failed (exitcode = 1)

I suggest detecting this error message and issuing a command :set -optP-include -optPdist/build/autogen/cabal_macros.h as pointed out at http://stackoverflow.com/questions/12546757/how-do-i-use-cabals-min-version-and-other-macros-with-ghci

If the header file is absent, haskell-mode can run a cabal build.

[chrisdone]

Agree. Technically cabal repl deals with this issue. But if one is unable to use cabal repl such a detection would be handy.

[hvr]

injecting a :set is the wrong approach here IMO; cabal repl support is what we want here

[chrisdone]

Another trick is putting this in your .ghci file of your project so that you only have to do this once.

[lykahb]

How can I detect if ghci or cabal repl was used?

[chrisdone]

How are you running GHCi?

[lykahb]

It is started by inferior-haskell I guess. I haven't used ghci for the modules which haskell-mode did not load.

[gracjan]

It has been over a ear since this issue was reported. It seems that todays cabal repl covers all use cases. Is this issue still relevant?

[gracjan]

I'll close this now. If you feel this is important just write below and we will reopen.