setup sdist places implementation-dependent preprocessor output in the source bundle

[bos]

(Imported from Trac #137, reported by ross on 2007-06-02)

e.g. happy -agc output in the haskell-src package.

Suggested new scheme: http://www.haskell.org/pipermail/cabal-devel/2007-May/000529.html.

[bos]

(Imported comment by ross on 2007-06-02)

see also #92: issues with 'clean'.

[bos]

(Imported comment by @igfoo on 2007-06-07)

It also includes files generated by "Setup configure", e.g. HsGLUT.h in the GLUT package.

[bos]

(Imported comment by @dcoutts on 2008-06-19)

Replying to @igfoo:

It also includes files generated by "Setup configure", e.g. HsGLUT.h in the GLUT package.

Which is because Cabal has no idea that HsGLUT.h is the result of HsGLUT.h.in.

[bos]

(Imported comment by ross on 2008-06-19)

Replying to @dcoutts:

Replying to @igfoo:

It also includes files generated by "Setup configure", e.g. HsGLUT.h in the GLUT package.

Which is because Cabal has no idea that HsGLUT.h is the result of HsGLUT.h.in.

Maybe #152 wasn't a bug.

[bos]

(Imported comment by @dcoutts on 2008-06-19)

Or maybe we should assume that foo is generated (by an unknown pre-processor) by foo.in (if foo.in exists) and so it is foo.in that should go in the sdist and not foo.

Though that also violates our rule about putting generated files in dist/ and not back in the source tree.

[bos]

(Imported comment by @igfoo on 2008-06-19)

Incidentally, include/HsGLUT.h is in extra-tmp-files; should Cabal look at that when deciding what to put in the sdist?

[bos]

(Imported comment by @dankna on 2008-06-20)

Attached, please find three patches for Cabal and one for
Cabal-Install, in "darcs send" format. Also find a change to Happy,
in the form of an entire Setup.lhs file to replace the corresponding
file in Happy-1.18.4 (I guess I must not have been able to find the
original repo for Happy - I can prepare a diff if you find that
easier). These implement the stuff we talked about with regard to
preprocessor output. Hopefully you'll like the way I did it. I'm
afraid it's only easy for me to test with ghc, but it /should/ support
all compilers, since I did make appropriate changes to all of their
backends. If this is a problem I can try to get the others set up,
but I hoped you might already be set for that and able to do it more
quickly than I could.

There are three main pieces to the patch, as the commit messages will
explain. Briefly, the first piece simply redirects the output, the
second piece makes sure the output is included in the sdist tarball,
and the third piece adds a user hook to implement the
subdirectory-naming policy we discussed.

With the redirection of the output, I found that by doing it at the
proper layer it wasn't necessary to add any new code to compare
timestamps; the existing codepath appeared to handle it. This could
use more testing; I used Happy as my test case.

With the inclusion in sdist, I added a new parameter to prepareTree,
which necessitated the change to Cabal-Install. As I explained in a
comment somewhere, it includes ALL immediate subdirectories of
preprocessed/, but within those, ONLY the files that have names which
could have been generated by a known preprocessor from one of the
included source files.

With the subdirectory-naming, I added a new user hook that implements
the concept of "specializing" the preprocessed output on a set of
variables. Rather than defining a new vocabulary of variables which
would then become maintenance overhead, I reused PathTemplateVariable?
for this purpose. It constructs a subdirectory name as a canonical
representation of the set of variables specialized on, with their
values. It uses URL-escaping for characters that we can't use for
various reasons.

I also made a trivial change to Happy's Setup.lhs, to test the
specialization feature. I've included that one too; once the Cabal
changes are released, either you or I can submit it to the Happy
maintainer for inclusion there. It doesn't actually implement using
Happy's --ghc option; it merely specializes the build properly,
outputting into "compiler=ghc-6.blahblahblah" if the compiler is GHC
or into "generic" otherwise. It does this by installing a
preprocesserSpecialization hook which looks at the LocalBuildInfo? it's
given, checks the compiler flavor therein, and returns [CompilerVar?]
or [] as appropriate. Hopefully this is a sufficiently general
capability for the use-cases that exist in the wild.

As always, see the source for more details. I tried to follow your
coding style as I understood it; in particular when I needed to add
imports I enumerated each symbol used. I also tried to comment
everything of any importance. I'll be interested in your feedback on
how well I managed.

[bos]

(Imported comment by @dankna on 2010-04-21)

Patch for Cabal in "darcs send" format.

[bos]

(Imported comment by @dankna on 2010-04-21)

Patch for Cabal-Install in "darcs send" format.

[bos]

(Imported comment by @dankna on 2010-04-21)

For testing purposes, modified Setup.lhs for Happy 1.18.4.

[bos]

(Imported comment by @nomeata on 2010-04-21)

Is there still something happening on this front? It seems that, for example, uuagc could greatly benefit if Setup sdist would include all the generated .hs files in the tarball required to bootstrap the program; the current scheme (a separate uuagc-bootstrap package) feels like unnecessary overkill to me.