Allow user configurable command line options for build tools

[dagit]

There is currently no mechanism to control how tools like happy are invoked by cabal. Other tools that would be nice to control over include (but not limited to), hsc2hs, c2hs, and alex.

A simple option would be to add a field happy-options: to the cabal file format. An even better solution would be for the mechanism to allow the options to be per module. An even better solution would make the addition of tools with options into a generic configurable option so that new build tools can be added without modifying cabal.

[elliottt]

This would be nice, and would give the package developer a bit of control back over how the tools get run.

[23Skidoo]

An even better solution would be for the mechanism to allow the options to be per module.

Probably best solved via tool-specific pragmas.

[23Skidoo]

With regard to this comment:

There is currently no mechanism to control how tools like happy are invoked by cabal.

This is not strictly true, you can set happy-options in ~/.cabal/config or use cabal configure --happy-options="...". But I agree that allowing happy-options in .cabal files would be nice.

[hvr]

I just noticed, one can workaround this also via a project-cabal.config file containing e.g.

-- workaround for https://github.com/haskell/cabal/issues/1223
program-default-options
  alex-options: --latin1

Not sure though if it's a good idea to include that file via extra-sources into the source-dist tarball, and whether it'll be honored then...

(It may actually be a good idea to reject package uploads to Hackage which contain a top-level cabal.config file...)

[yav]

I just run into the same issue. This seems like a fairly obvious and trivial feature, and this ticket is over 5 years old. Are there any technical difficulties, or are we just lacking manpower?

[23Skidoo]

Patches definitely welcome.

[yav]

I found that Alex has an "encoding" directive, so one can do:

%encoding "latin1"

instead of passing --latin1, which is a work around for this specific case.