foreign-library does not apply pkgconfig-depends cflags to c-sources when using v2-build

[tathougies]

Describe the bug

When building a foreign-library with c-sources and pkgconfig-depends, Cabal 3.14.1 (with GHC 9.10.1) fails to propagate the pkg-config CFLAGS (-I/...) to the C compiler invocation.

I'm trying to use glib, and as a result, C code that includes <glib.h> / <gobject.h> etc fails to build, even though the same pkgconfig-depends works correctly for library and executable components.

To Reproduce

Make a cabal file with a foreign-library that uses a pkgconfig-depends library. Note that when running with --verbose, the files fail to build.

$ cabal build ...

Expected behavior

I would expect it to be the same as with library.

System information

• Operating system: NixOS 24.05
• cabal: 3.14
• ghc: 9.10.1

Additional context

[tathougies]

If it helps, this is my file:

cabal-version: 2.4

name:           honey-ui
version:        0.0.0
build-type:     Custom

custom-setup
  setup-depends:
      base
    , Cabal
    , process

foreign-library libhoney
  type: native-shared
  lib-version-info: 0:1:0

  other-modules:
    Honey.UI.Common

  default-extensions:
      OverloadedStrings
      OverloadedLabels
      ForeignFunctionInterface
      LambdaCase
  build-depends:
      base
    , bytestring
    , text
  default-language: Haskell2010

  pkgconfig-depends: glib-2.0, gobject-2.0, gtk4
  c-sources: csrc/honey_context.c

Common.hs is blank

module Honey.UI.Common where

honey_context.c is something that just wants to import glib.h:

#include <glib.h>

...

This works if you just turn foreign-library into library.

[tathougies]

This Setup.hs fixes the issue, if that helps:

import Distribution.Simple
import Distribution.Simple.Setup
import Distribution.Simple.LocalBuildInfo
import Distribution.PackageDescription
import Distribution.Types.BuildInfo
import Distribution.Types.PackageDescription
import Distribution.Types.CondTree
import Distribution.Types.ForeignLib
import Distribution.Types.UnqualComponentName
import Distribution.Utils.Path
import System.Process
import Data.List (intercalate, nub)

main :: IO ()
main = defaultMainWithHooks $ simpleUserHooks
  { confHook = patchedConfHook }

-- | Wrap the default confHook, but modify the BuildInfo for foreign-library 'libhoney'
patchedConfHook
  :: (GenericPackageDescription, HookedBuildInfo)
  -> ConfigFlags
  -> IO LocalBuildInfo
patchedConfHook (gpd, hbi) flags = do
    let flibs = condForeignLibs gpd
    flibs' <- mapM tweakFL flibs
    let gpd' = gpd { condForeignLibs = flibs' }
    confHook simpleUserHooks (gpd', hbi) flags
  where
    tweakFL :: (UnqualComponentName, CondTree v c ForeignLib)
            -> IO (UnqualComponentName, CondTree v c ForeignLib)
    tweakFL (name, tree)
      -- Only modify the foreign-library named "libhoney"
      | name == mkUnqualComponentName "libhoney" =
          (,) name <$> sequence (fmap tweakFL' tree)
      | otherwise = pure (name, tree)

    tweakFL' :: ForeignLib -> IO ForeignLib
    tweakFL' fl = do
      let bi  = foreignLibBuildInfo fl
          pkgs = [ unPkgconfigName name
                 | PkgconfigDependency name _range <- pkgconfigDepends bi
                 ]
      bi' <- addPkgConfigFlags pkgs bi
      pure fl { foreignLibBuildInfo = bi' }


    addPkgConfigFlags :: [String] -> BuildInfo -> IO BuildInfo
    addPkgConfigFlags pkgs bi = do
      ccOptions' <- runPKG "--cflags" pkgs
      ldOptions' <- runPKG "--libs" pkgs
      pure bi { ccOptions = ccOptions bi ++ ccOptions'
              , ldOptions = ldOptions bi ++ ldOptions'
              }

    runPKG :: String -> [String] -> IO [String]
    runPKG opt pkgs =
        case pkgs of
          [] -> pure []
          _  -> words <$> readProcess "pkg-config" (opt : pkgs) ""

[zlonast]

I haven't checked, but it seems like my pull request fixes this. #10969