Haskell - Packaging cabal package with custom preprocessors - haskell

Question

I've implemented a custom preprocessor which creates *.hs files form *.tpl files. It is specified in Setup.hs by using a Build-Type: Custom. Everything works fine, but I can't create tar.gz package from it (using cabal sdist).
Cabal complains, that it can not find the exposed modules which are generated by the preprocessor. The error message is
cabal: Error: Could not find module with any
suffix: ["gc","chs","hsc","x","y","ly","cpphs","hs","lhs"]
How can I make Cabal aware of the fact that the module is not missing, or maybe add tpl to the known file extensions, or something?

Answer 1

This is a known issue with cabal sdist. Use ./dist/setup/setup sdist instead.
Here's an example:
$ cat preprocessor-test.cabal
name: preprocessor-test
version: 0.1.0.0
build-type: Custom
cabal-version: >=1.10
extra-source-files: PreprocessorTest/*.prepro
library
exposed-modules: PreprocessorTest.PreprocessorTest
build-depends: base ==4.5.*
-- hs-source-dirs:
default-language: Haskell2010
$ cat Setup.hs
#!/usr/bin/env runhaskell
import Distribution.Simple
import Distribution.Simple.PreProcess
import Distribution.Simple.Utils
import Distribution.PackageDescription
import Distribution.Simple.LocalBuildInfo
import System.Cmd (rawSystem)
import System.FilePath ((</>))
main = let hooks = simpleUserHooks
dummy = ("prepro", dummyPreprocessor)
in defaultMainWithHooks hooks
{ hookedPreProcessors = dummy:knownSuffixHandlers }
dummyPreprocessor :: BuildInfo -> LocalBuildInfo -> PreProcessor
dummyPreprocessor build local = PreProcessor {
platformIndependent = True,
runPreProcessor =
mkSimplePreProcessor $ \inFile outFile verbosity -> do
notice verbosity (inFile ++ " is being preprocessed to " ++ outFile)
rawSystem "cp" [inFile, outFile]
return ()
}
$ cat PreprocessorTest/PreprocessorTest.prepro
module PreprocessorTest.PreprocessorTest
where
preprocessorTest :: Int
preprocessorTest = 1
$ cabal configure
Resolving dependencies...
[1 of 1] Compiling Main ( Setup.hs, dist/setup/Main.o )
Linking ./dist/setup/setup ...
Configuring preprocessor-test-0.1.0.0...
$ cabal build
Building preprocessor-test-0.1.0.0...
Preprocessing library preprocessor-test-0.1.0.0...
PreprocessorTest/PreprocessorTest.prepro is being preprocessed to
dist/build/PreprocessorTest/PreprocessorTest.hs
[1 of 1] Compiling PreprocessorTest.PreprocessorTest ( dist/build/PreprocessorTest/PreprocessorTest.hs, dist/build/PreprocessorTest/PreprocessorTest.o )
Registering preprocessor-test-0.1.0.0...
$ ./dist/setup/setup sdist
Distribution quality errors:
No 'synopsis' or 'description' field.
The 'license' field is missing or specified as AllRightsReserved.
Distribution quality warnings:
No 'category' field.
No 'maintainer' field.
Note: the public hackage server would reject this package.
Building source dist for preprocessor-test-0.1.0.0...
Preprocessing library preprocessor-test-0.1.0.0...
PreprocessorTest/PreprocessorTest.prepro is being preprocessed to
dist/src/sdist.-6767/preprocessor-test-0.1.0.0/dist/build/PreprocessorTest/PreprocessorTest.hs
Source tarball created: dist/preprocessor-test-0.1.0.0.tar.gz
$ tar tzf dist/preprocessor-test-0.1.0.0.tar.gz
preprocessor-test-0.1.0.0/
preprocessor-test-0.1.0.0/dist/
preprocessor-test-0.1.0.0/dist/build/
preprocessor-test-0.1.0.0/dist/build/PreprocessorTest/
preprocessor-test-0.1.0.0/dist/build/PreprocessorTest/PreprocessorTest.hs
preprocessor-test-0.1.0.0/Setup.hs
preprocessor-test-0.1.0.0/PreprocessorTest/
preprocessor-test-0.1.0.0/PreprocessorTest/PreprocessorTest.prepro
preprocessor-test-0.1.0.0/preprocessor-test.cabal