01/03: gnu: ghc-9.2: Make Cabal respect GHC_PACKAGE_PATH

[guix-commits]

lbraun pushed a commit to branch haskell-team
in repository guix.

commit 645ff0c9e41396ac66149aefa10f9dd0badf93c2
Author: Sören Tempel <soeren@soeren-tempel.net>
AuthorDate: Tue Dec 19 11:05:32 2023 +0100

    gnu: ghc-9.2: Make Cabal respect GHC_PACKAGE_PATH
    
    **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
---
 gnu/local.mk                                       |  1 +
 gnu/packages/haskell.scm                           |  3 +-
 .../ghc-9.2-cabal-support-package-path.patch       | 67 ++++++++++++++++++++++
 3 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/gnu/local.mk b/gnu/local.mk
index 83b7402b09..f537a290a3 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1329,6 +1329,7 @@ dist_patch_DATA =                                         
\
   %D%/packages/patches/geoclue-config.patch                    \
   %D%/packages/patches/gettext-libunicode-update.patch         \
   %D%/packages/patches/ghc-8.0-fall-back-to-madv_dontneed.patch        \
+  %D%/packages/patches/ghc-9.2-cabal-support-package-path.patch \
   %D%/packages/patches/ghc-9.2-glibc-2.33-link-order.patch \
   %D%/packages/patches/ghc-9.2-grep-warnings.patch \
   %D%/packages/patches/ghc-testsuite-dlopen-pie.patch          \
diff --git a/gnu/packages/haskell.scm b/gnu/packages/haskell.scm
index 6d8675d37e..9a158c0151 100644
--- a/gnu/packages/haskell.scm
+++ b/gnu/packages/haskell.scm
@@ -1444,7 +1444,8 @@ interactive environment for the functional language 
Haskell.")
                 (sha256
                  (base32
                   "07028i0hm74svvq9b3jpkczaj6lsdgn3hgr4wa7diqiq3dypj1h6"))
-                (patches (search-patches 
"ghc-9.2-glibc-2.33-link-order.patch"))))
+                (patches (search-patches "ghc-9.2-glibc-2.33-link-order.patch"
+                                         
"ghc-9.2-cabal-support-package-path.patch"))))
       (arguments
        (substitute-keyword-arguments (package-arguments base)
          ((#:phases phases '%standard-phases)
diff --git a/gnu/packages/patches/ghc-9.2-cabal-support-package-path.patch 
b/gnu/packages/patches/ghc-9.2-cabal-support-package-path.patch
new file mode 100644
index 0000000000..9e4c405c50
--- /dev/null
+++ b/gnu/packages/patches/ghc-9.2-cabal-support-package-path.patch
@@ -0,0 +1,67 @@
+Without this patch, Cabal terminates if GHC_PACKAGE_PATH is set. This is
+an annoyance with Guix as it makes heavy use of GHC_PACKAGE_PATH to have
+GHC pickup Haskell package installed via Guix. Therefore, Cabal does
+presently not work by default in environments created by Guix. This is
+a workaround which makes Cabal respect GHC_PACKAGE_PATH.
+
+Taken from https://github.com/haskell/cabal/issues/3728
+
+diff -upr a/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs 
b/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs
+--- a/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs     2022-11-06 
20:41:17.000000000 +0100
++++ b/libraries/Cabal/Cabal/src/Distribution/Simple/GHC.hs     2023-12-18 
14:34:15.148911717 +0100
+@@ -71,6 +71,7 @@ module Distribution.Simple.GHC (
+  ) where
+ 
+ import Prelude ()
++import Distribution.Compat.Environment (lookupEnv)
+ import Distribution.Compat.Prelude
+ 
+ import qualified Distribution.Simple.GHC.Internal as Internal
+@@ -117,7 +118,7 @@ import System.Directory
+          , canonicalizePath, removeFile, renameFile, getDirectoryContents )
+ import System.FilePath          ( (</>), (<.>), takeExtension
+                                 , takeDirectory, replaceExtension
+-                                ,isRelative )
++                                , isRelative, searchPathSeparator )
+ import qualified System.Info
+ #ifndef mingw32_HOST_OS
+ import System.Posix (createSymbolicLink)
+@@ -333,9 +334,11 @@ getInstalledPackages :: Verbosity -> Com
+                      -> ProgramDb
+                      -> IO InstalledPackageIndex
+ getInstalledPackages verbosity comp packagedbs progdb = do
+-  checkPackageDbEnvVar verbosity
+   checkPackageDbStack verbosity comp packagedbs
+-  pkgss <- getInstalledPackages' verbosity packagedbs progdb
++  envPackageDBs <-
++    maybe [] (map SpecificPackageDB . unintersperse searchPathSeparator)
++      <$> lookupEnv "GHC_PACKAGE_PATH"
++  pkgss <- getInstalledPackages' verbosity (envPackageDBs ++ packagedbs) 
progdb
+   index <- toPackageIndex verbosity pkgss progdb
+   return $! hackRtsPackage index
+ 
+@@ -405,10 +408,6 @@ getUserPackageDB _verbosity ghcProg plat
+     packageConfFileName = "package.conf.d"
+     ghcVersion = fromMaybe (error "GHC.getUserPackageDB: no ghc version") $ 
programVersion ghcProg
+ 
+-checkPackageDbEnvVar :: Verbosity -> IO ()
+-checkPackageDbEnvVar verbosity =
+-    Internal.checkPackageDbEnvVar verbosity "GHC" "GHC_PACKAGE_PATH"
+-
+ checkPackageDbStack :: Verbosity -> Compiler -> PackageDBStack -> IO ()
+ checkPackageDbStack verbosity comp =
+     if flagPackageConf implInfo
+@@ -461,8 +460,11 @@ getInstalledPackagesMonitorFiles :: Verb
+                                  -> ProgramDb
+                                  -> [PackageDB]
+                                  -> IO [FilePath]
+-getInstalledPackagesMonitorFiles verbosity platform progdb =
+-    traverse getPackageDBPath
++getInstalledPackagesMonitorFiles verbosity platform progdb packageDBs = do
++    envPackageDBs <-
++      maybe [] (map SpecificPackageDB . unintersperse searchPathSeparator)
++        <$> lookupEnv "GHC_PACKAGE_PATH"
++    traverse getPackageDBPath (envPackageDBs ++ packageDBs)
+   where
+     getPackageDBPath :: PackageDB -> IO FilePath
+     getPackageDBPath GlobalPackageDB =