setup haddock ignores LANGUAGE CPP pragma

[bos]

(Imported from Trac #230, reported by ross on 2008-02-04)

setup haddock preprocesses sources with cpp if CPP is included in the extensions field, but not if a source file starts with

{-# LANGUAGE CPP #-}

This is confusing, because that works with setup build.

[bos]

(Imported comment by @dcoutts on 2008-02-04)

Of course that's because it is GHC that interprets the {-# LANGUAGE CPP #-} pragma and not Cabal.

Long term I think Cabal should notice LANGUAGE pragmas. It'd allow it to check that all extensions are declared in the .cabal file and it'd allow Cabal to do the cpping itself rather than using ghc's cpp.

I'm assigning it to milestone 2.0 because it should be easy enough if we're already reading .hs files to do module chasing.

[bos]

(Imported comment by ross on 2008-02-04)

Distribution.Simple.Hugs.getOptionsFromSource may be useful.

[bos]

(Imported comment by @dcoutts on 2008-02-05)

And of course we have the same problem with {-# OPTIONS -fglasgow-exts -cpp #-} which is generated by alex. So even if you didn't realise you use CPP, if you use alex then you do and then haddock fails because we don't run cpp on that file. So if we go looking for LANGUAGE pragmas then we'd also have to do the same for OPTIONS (and OPTIONS_*) pragmas.

Seems that getOptionsFromSource gets those too which is nice. Perhaps we should just do that for every file in builds and when haddocking.

[tibbe]

This works for me now so I guess it got fixed at some point.

[asr]

Why is this issue closed? I could reproduce the issue with Cabal-1.18.0 and cabal-install-1.18.0.

[tibbe]

Why is this issue closed? I could reproduce the issue with Cabal-1.18.0 and cabal-install-1.18.0.

I said 7 months ago:

This works for me now so I guess it got fixed at some point.

Perhaps it broken again. Do you have simple complete repro example?

[asr]

Do you have simple complete repro example?

Yes. See https://github.com/asr/cabal-issue223

If I remove extensions: CPP from issue223.cabal I got (I only could reproduce the issue using the #include directive):

$ cabal haddock --executables
Running Haddock for issue223-0.1...
Preprocessing executable 'issue223' for issue223-0.1...

dist/build/tmp-14523/Main.hs:5:0:
     fatal error: Empty.h: No such file or directory
compilation terminated.

[asr]

I could reproduce the issue with

$ cabal --v
cabal-install version 1.20.0.1
using version 1.20.0.0 of the Cabal library

Could someone reopen the issue please.

[jgm]

I just ran into this too with jgm/zip-archive.
Interestingly, removing Default-Extensions: CPP from the cabal file fixed the problem.

[23Skidoo]

/me wonders if this has been fixed by #1854.

[asr]

I requested reopen the issue some days ago. The issue is fixed by #1854. Thanks!

[23Skidoo]

@asr Great. Closing.