OK. If there is a simple patch which can help support your use case better, we'd be happy to take it. However, I don't think a design like this is the right long term plan. The correct long term plan, I think, is to do something like ToolCabal https://github.com/TiborIntelSoft/ToolCabal and make it so that you can just plug in custom build rules of your own, which can include preprocessor processing. This will also fix some of our other problems, such as the fact that we repeatedly preprocess executables even when it's not necessary https://github.com/haskell/cabal/issues/2432 I'm hoping to take a crack at this at some point; hopefully your boilerplate will tide you until then. Edward Excerpts from Andrey Sverdlichenko's message of 2016-03-07 10:45:56 -0800:

Hi Edward,

I can do with current Cabal, it is just a lot of boilerplate and inconvenience. What I would like to have as an ideal solution for my problem is a preprocessor interface similar to PPSuffixHandler, but with extra capabilities. It should receive one file as an input, but be able to generate multiple modules with the names of its own choosing. And I want the resulting modules to be added to all build steps automatically. So it should looks approximately like this:

data SmartPreProcessor = SmartPreProcessor { platformIndependent :: Bool, runPreProcessor :: (FilePath, FilePath) -- Location of the source file relative to a base dir -> Verbosity -- verbosity -> FilePath -- output base dir -> IO [FilePath] -- output sources files. Should exit if the preprocessor fails }

There may be design objections to such preprocessor, but again, this is an ideal solution to my problem.

On Sun, Mar 6, 2016 at 11:55 PM Edward Z. Yang wrote:

...

Hello Andrey,

I do not know what the right way to sovle your problem is, but if it is indeed the case that this cannot be done with Cabal, speaking as a Cabal developer, we definitely should try to fix this. A bug report would be much appreciated.

...

So, I have buildHook, copyHook and regHook replaced with wrappers which change PackageDescription parameter and call original function. Library is built and installed, but somewhere between build and copy actions there is still a message "Warning: modules not listed in foo.cabal for library component (add to other-modules)". I can't identify where it comes from.

I'm pretty sure this message comes from Stack; src/Stack/Types/Package.hs.

Cheers, Edward