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**tl;dr** Applying this patch makes Cabal work in Guix environments and ensures that Cabal picks up Haskell packages installed via Guix. Guix makes heavy use of GHC_PACKAGE_PATH to make GHC pickup Haskell packages installed via the Guix package manager. The environment variable is set using native-search-paths from the GHC packages. Unfortunately, upstream Cabal does presently not respect GHC_PACKAGE_PATH. If this environment variable is set, `cabal build` and other commands will terminate. For building packages, Guix does not make much use of cabal-install hence this is not as big of an issue. However, cabal-install does therefore presently not work out-of-the-box in environments created by Guix. For example, in `guix shell` environments. This makes it essentially impossible to use Guix for setting up development environments for Haskell software. Cabal upstream is aware of this issue and a patch exists to workaround this problem. The patch is currently not merged upstream due to issues related to reconfiguration (changing GHC_PACKAGE_PATH between `cabal configure` and `cabal build`). However, I would argue that this edge case is not that relevant for Guix and therefore propose including this patch with the Cabal Guix package. As outlined above, cabal-install is not usable by default presently, and I would therefore argue that this is a major improvement over the current situation. I am willing to work with Cabal upstream to have this issue fixed upstream eventually. Note that this requires patching the GHC package instead of the cabal-install package as Guix uses the version of the Cabal package <https://hackage.haskell.org/package/Cabal> distributed with GHC. See: https://github.com/haskell/cabal/issues/3728 * gnu/packages/haskell-apps.scm (cabal-install): Include patch to support the GHC_PACKAGE_PATH environment variable. Signed-off-by: Sören Tempel <soeren@soeren-tempel.net> Signed-off-by: Lars-Dominik Braun <lars@6xq.net> Change-Id: Ib77ffa937b878690d0e2d8964b534842b99da039
67 lines
3.2 KiB
Diff
67 lines
3.2 KiB
Diff
Without this patch, Cabal terminates if GHC_PACKAGE_PATH is set. This is
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an annoyance with Guix as it makes heavy use of GHC_PACKAGE_PATH to have
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GHC pickup Haskell package installed via Guix. Therefore, Cabal does
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presently not work by default in environments created by Guix. This is
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a workaround which makes Cabal respect GHC_PACKAGE_PATH.
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Taken from https://github.com/haskell/cabal/issues/3728
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diff -upr a/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs b/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs
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--- a/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs 2022-11-06 20:41:17.000000000 +0100
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+++ b/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs 2023-12-18 14:34:15.148911717 +0100
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@@ -71,6 +71,7 @@ module Distribution.Simple.GHC (
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) where
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import Prelude ()
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+import Distribution.Compat.Environment (lookupEnv)
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import Distribution.Compat.Prelude
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import qualified Distribution.Simple.GHC.Internal as Internal
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@@ -117,7 +118,7 @@ import System.Directory
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, canonicalizePath, removeFile, renameFile, getDirectoryContents )
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import System.FilePath ( (</>), (<.>), takeExtension
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, takeDirectory, replaceExtension
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- ,isRelative )
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+ , isRelative, searchPathSeparator )
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import qualified System.Info
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#ifndef mingw32_HOST_OS
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import System.Posix (createSymbolicLink)
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@@ -333,9 +334,11 @@ getInstalledPackages :: Verbosity -> Com
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-> ProgramDb
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-> IO InstalledPackageIndex
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getInstalledPackages verbosity comp packagedbs progdb = do
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- checkPackageDbEnvVar verbosity
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checkPackageDbStack verbosity comp packagedbs
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- pkgss <- getInstalledPackages' verbosity packagedbs progdb
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+ envPackageDBs <-
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+ maybe [] (map SpecificPackageDB . unintersperse searchPathSeparator)
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+ <$> lookupEnv "GHC_PACKAGE_PATH"
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+ pkgss <- getInstalledPackages' verbosity (envPackageDBs ++ packagedbs) progdb
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index <- toPackageIndex verbosity pkgss progdb
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return $! hackRtsPackage index
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@@ -405,10 +408,6 @@ getUserPackageDB _verbosity ghcProg plat
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packageConfFileName = "package.conf.d"
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ghcVersion = fromMaybe (error "GHC.getUserPackageDB: no ghc version") $ programVersion ghcProg
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-checkPackageDbEnvVar :: Verbosity -> IO ()
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-checkPackageDbEnvVar verbosity =
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- Internal.checkPackageDbEnvVar verbosity "GHC" "GHC_PACKAGE_PATH"
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-
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checkPackageDbStack :: Verbosity -> Compiler -> PackageDBStack -> IO ()
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checkPackageDbStack verbosity comp =
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if flagPackageConf implInfo
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@@ -461,8 +460,11 @@ getInstalledPackagesMonitorFiles :: Verb
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-> ProgramDb
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-> [PackageDB]
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-> IO [FilePath]
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-getInstalledPackagesMonitorFiles verbosity platform progdb =
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- traverse getPackageDBPath
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+getInstalledPackagesMonitorFiles verbosity platform progdb packageDBs = do
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+ envPackageDBs <-
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+ maybe [] (map SpecificPackageDB . unintersperse searchPathSeparator)
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+ <$> lookupEnv "GHC_PACKAGE_PATH"
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+ traverse getPackageDBPath (envPackageDBs ++ packageDBs)
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where
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getPackageDBPath :: PackageDB -> IO FilePath
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getPackageDBPath GlobalPackageDB =
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