Cabal should respect PKG_CONFIG

[wenkokke]

Describe the bug Cabal should probably respect the PKG_CONFIG environment variable, rather than hard-coding the name "pkg-config", as done in, e.g., Distribution.Simple.Program.Builtin. For instance, mingw packages are moving to use pkgconf, which leads to trouble with Cabal, as pkg-config and pkgconf cannot both be installed.

[mouse07410]

If memory serves me, PKG_CONFIG env var is used by other package managers, besides Cabal. Thus, relying on it here could be problematic.

[gbaz]

Is that env var documented as a standard anywhere or is it just widespread convention?

[mouse07410]

I can't recall. Sorry!

[arrowd]

FreeBSD also uses pkgconf but we also install the pkg-config symlink pointing to pkgconf. Maybe MinGW should do the same?

If an utility is intended to be a drop-in replacement and not intended to be coinstalled, I'd rather fix it on the packaging side.

[jokeyrhyme]

I did brew install pkgconf instead of brew install pkg-config and ran into the following problem during cabal install pandoc-cli:

nu ❯ cabal install pandoc-cli
Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.6.2.0 supports
'ghc' version < 9.4): /Users/rwaldon/.ghcup/bin/ghc is version 9.4.8
Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.6.2.0 supports
'ghc' version < 9.4): /Users/rwaldon/.ghcup/bin/ghc is version 9.4.8
Resolving dependencies...
Build profile: -w ghc-9.4.8 -O1
In order, the following will be built (use -v for more details):
 - digest-0.0.2.1 (lib) (requires build)
 - zlib-0.7.1.0 (lib) (requires build)
 - zip-archive-0.4.3.2 (lib) (requires build)
 - streaming-commons-0.2.2.6 (lib) (requires build)
 - JuicyPixels-3.3.9 (lib) (requires build)
 - hslua-module-zip-1.1.3 (lib) (requires build)
 - http-client-0.7.17 (lib) (requires build)
 - conduit-extra-1.3.6 (lib) (requires build)
 - http-client-tls-0.3.6.3 (lib) (requires build)
 - xml-conduit-1.9.1.3 (lib:xml-conduit) (requires build)
 - typst-0.5.0.5 (lib) (requires build)
 - skylighting-core-0.14.2 (lib) (requires build)
 - pandoc-3.2.1 (lib:xml-light) (requires build)
 - citeproc-0.8.1.1 (lib) (requires build)
 - skylighting-format-ansi-0.1 (lib) (requires build)
 - skylighting-format-latex-0.1 (lib) (requires build)
 - skylighting-format-context-0.1.0.2 (lib) (requires build)
 - skylighting-format-blaze-html-0.1.1.2 (lib) (requires build)
 - skylighting-0.14.2 (lib) (requires build)
 - pandoc-3.2.1 (lib) (requires build)
 - pandoc-lua-engine-0.3 (lib) (requires build)
 - pandoc-cli-3.2.1 (exe:pandoc) (requires build)
Starting     zlib-0.7.1.0 (lib)
Starting     digest-0.0.2.1 (lib)

Failed to build digest-0.0.2.1. The failure occurred during the configure
step.
Build log ( /Users/rwaldon/.cabal/logs/ghc-9.4.8/dgst-0.0.2.1-e2b06c6e.log ):
Configuring library for digest-0.0.2.1..
cabal-3.6.2.0-p1: The program 'pkg-config' version >=0.9.0 is required but it
could not be found.

Failed to build zlib-0.7.1.0. The failure occurred during the configure step.
Build log ( /Users/rwaldon/.cabal/logs/ghc-9.4.8/zlb-0.7.1.0-e4067dc5.log ):
Configuring library for zlib-0.7.1.0..
cabal-3.6.2.0-p1: The program 'pkg-config' version >=0.9.0 is required but it
could not be found.

cabal: Failed to build digest-0.0.2.1 (which is required by exe:pandoc from
pandoc-cli-3.2.1). See the build log above for details.
Failed to build zlib-0.7.1.0 (which is required by exe:pandoc from
pandoc-cli-3.2.1). See the build log above for details.

Is every package going to need to be updated individually or is there something that can be done at the cabal level?

[Bodigrim]

@jokeyrhyme both of your issues should be resolved by updating Cabal to 3.10+. Cabal 3.6.2.0, which you use, is very much outdated.

[jokeyrhyme]

@Bodigrim bah, that's embarrassing: my update scripts have been running ghcup install cabal all this time instead of ghcup install cabal latest, oops!

Yep, running ghcup install cabal latest and then cabal install pandoc-cli works perfectly

Cheers! <3