create cabal files

[pascalh]

This pull request allows bnfc to create cabal files in order to build/install the generated modules.

(I will start working on a cabal hook, which lets you use bnfc as a preprocessor to cabal.)

[gdetrez]

Hi @pascalh. Thanks for this 👍 and for taking time to add tests ❤️

I see from the code that it should add the proper dependencies but when trying on my local machine, the generated build-depends: is empty, any idea why that might be?

Also, would it be possible to also build the test program?

[pascalh]

I can not imagine why the dependencies are not being added on your machine. Which ghc and cabal version are you using? If this is a major problem we could generate the cabal files without cabal library (using plain text concatenation).

Building the test program is not straight forward, because the module and file name differ. I could rename the module Main and everything works fine. I felt like this is a bigger change, which should not be implemented without any discussion.

[gdetrez]

It took me a while but I manage to make some more tests. I am using ghc 7.8 and Cabal (library) 1.18. I tried rebuilding bnfc with Cabal 1.22 and it now correctly populates the list of dependencies. So it might just be a bug in old Cabal library and I guess one solution is to make the lower version bound higher (1.22 seems to work, 1.20 might as well)

I'm not sure I understand what is the problem with the test executable. I tried adding a section to the cabal file manually and it seems to work fine.
What I added looks like this (there might be a way to make it less redundant though...)

Executable TestCalc
   build-depends:
     base >4,
     array -any
   main-is: TestCalc.hs
   Other-modules:
     AbsCalc
     ErrM
     PrintCalc
     LexCalc
     ParCalc

[pascalh]

Thanks for testing. It worked out well using your approach.

[andreasabel]

Seems like @gdetrez has moved on, this threat has been dormant for a year.
I am the new guy trying to take over some maintenance for bnfc (I use it for my class).

What is the status of this feature @pascalh ?

• Still interested.
• Good test coverage.
• Good documentation (integration into bnfc-tutorial, for instance).

[pascalh]

@andreasabel Great to see BNFC coming back to life. I will update the pull request as soon as I find some time to do so.

[andreasabel]

Possibly cabal init could be utilized to generate the cabal file, see haskell/cabal#7253 .
I also played with hpack, see sol/hpack#406 .