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Sören Tempel 9236047476
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
2024-06-29 08:56:16 +02:00
.mumi
build-aux
doc services: guix: Default `channels' field to #f. 2024-06-26 23:36:24 +02:00
etc etc: Add explicit ‘--substitute-urls’ in guix-daemon service files. 2024-06-26 22:59:55 +02:00
gnu gnu: ghc-9.2: Make Cabal respect GHC_PACKAGE_PATH 2024-06-29 08:56:16 +02:00
guix swh: Specify 'extid_version' when looking up by external ID. 2024-06-26 23:56:56 +02:00
m4
nix etc: Add explicit ‘--substitute-urls’ in guix-daemon service files. 2024-06-26 22:59:55 +02:00
po
scripts
tests
.dir-locals.el
.editorconfig
.gitattributes
.gitignore
.guix-authorizations
.guix-channel
.mailmap
.patman
AUTHORS
bootstrap
ChangeLog
CODE-OF-CONDUCT
config-daemon.ac etc: Add explicit ‘--substitute-urls’ in guix-daemon service files. 2024-06-26 22:59:55 +02:00
configure.ac
COPYING
gnu.scm
guix.scm
HACKING
Makefile.am
manifest.scm manifest: Streamline; add packages useful for patch review/submission. 2024-06-24 08:51:43 -04:00
NEWS
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-*- mode: org -*-

[[https://www.gnu.org/software/guix/][GNU Guix]] (IPA: /ɡiːks/) is a purely functional package manager, and
associated free software distribution, for the [[https://www.gnu.org/gnu/gnu.html][GNU system]].  In addition
to standard package management features, Guix supports transactional
upgrades and roll-backs, unprivileged package management, per-user
profiles, and garbage collection.

It provides [[https://www.gnu.org/software/guile/][Guile]] Scheme APIs, including a high-level embedded
domain-specific languages (EDSLs) to describe how packages are to be
built and composed.

GNU Guix can be used on top of an already-installed GNU/Linux distribution, or
it can be used standalone (we call that “Guix System”).

Guix is based on the [[https://nixos.org/nix/][Nix]] package manager.


* Requirements

If you are building Guix from source, please see the manual for build
instructions and requirements, either by running:

  info -f doc/guix.info "Requirements"

or by checking the [[https://guix.gnu.org/manual/en/html_node/Requirements.html][web copy of the manual]].

* Installation

See the manual for the installation instructions, either by running

  info -f doc/guix.info "Installation"

or by checking the [[https://guix.gnu.org/manual/en/html_node/Installation.html][web copy of the manual]].

* Building from Git

For information on building Guix from a Git checkout, please see the relevant
section in the manual, either by running

  info -f doc/guix.info "Building from Git"

or by checking the [[https://guix.gnu.org/manual/en/html_node/Building-from-Git.html][web_copy of the manual]].

* How It Works

Guix does the high-level preparation of a /derivation/.  A derivation is
the promise of a build; it is stored as a text file under
=/gnu/store/xxx.drv=.  The (guix derivations) module provides the
`derivation' primitive, as well as higher-level wrappers such as
`build-expression->derivation'.

Guix does remote procedure calls (RPCs) to the build daemon (the =guix-daemon=
command), which in turn performs builds and accesses to the store on its
behalf.  The RPCs are implemented in the (guix store) module.

* Contact

GNU Guix is hosted at https://savannah.gnu.org/projects/guix/.

Please email <help-guix@gnu.org> for questions and <bug-guix@gnu.org> for bug
reports; email <gnu-system-discuss@gnu.org> for general issues regarding the
GNU system.

Join #guix on irc.libera.chat.

* Guix & Nix

GNU Guix is based on [[https://nixos.org/nix/][the Nix package manager]].  It implements the same
package deployment paradigm, and in fact it reuses some of its code.
Yet, different engineering decisions were made for Guix, as described
below.

Nix is really two things: a package build tool, implemented by a library
and daemon, and a special-purpose programming language.  GNU Guix relies
on the former, but uses Scheme as a replacement for the latter.

Using Scheme instead of a specific language allows us to get all the
features and tooling that come with Guile (compiler, debugger, REPL,
Unicode, libraries, etc.)  And it means that we have a general-purpose
language, on top of which we can have embedded domain-specific languages
(EDSLs), such as the one used to define packages.  This broadens what
can be done in package recipes themselves, and what can be done around them.

Technically, Guix makes remote procedure calls to the nix-worker
daemon to perform operations on the store.  At the lowest level, Nix
“derivations” represent promises of a build, stored in .drv files in
the store.  Guix produces such derivations, which are then interpreted
by the daemon to perform the build.  Thus, Guix derivations can use
derivations produced by Nix (and vice versa).

With Nix and the [[https://nixos.org/nixpkgs][Nixpkgs]] distribution, package composition happens at
the Nix language level, but builders are usually written in Bash.
Conversely, Guix encourages the use of Scheme for both package
composition and builders.  Likewise, the core functionality of Nix is
written in C++ and Perl; Guix relies on some of the original C++ code,
but exposes all the API as Scheme.

* Related software

  - [[https://nixos.org][Nix, Nixpkgs, and NixOS]], functional package manager and associated
    software distribution, are the inspiration of Guix
  - [[https://www.gnu.org/software/stow/][GNU Stow]] builds around the idea of one directory per prefix, and a
    symlink tree to create user environments
  - [[https://www.pvv.ntnu.no/~arnej/store/storedoc_6.html][STORE]] shares the same idea
  - [[https://live.gnome.org/OSTree/][GNOME's OSTree]] allows bootable system images to be built from a
    specified set of packages
  - The [[https://www.gnu.org/s/gsrc/][GNU Source Release Collection]] (GSRC) is a user-land software
    distribution; unlike Guix, it relies on core tools available on the
    host system