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meta.pkgConfigModules: Init convention

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See docs.

Follow-up work:

- Existing packages should be converted

- `defaultPkgConfigPackages` should assert on `meta.pkgConfigModules`
  and let `tests.pkg-config` alone test the build results.

CC @sternenseemann

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
This commit is contained in:
John Ericson 2023-02-02 23:49:15 -05:00
parent 3dcde1c342
commit 6e4a1b18d9
5 changed files with 65 additions and 3 deletions
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48
doc/languages-frameworks/pkg-config.section.md
View file

@ -4,6 +4,48 @@
Nixpkgs provides a couple of facilities for working with this tool.
- A [setup hook](#setup-hook-pkg-config) bundled with in the `pkg-config` package, to bring a derivation's declared build inputs into the environment.
- The [`validatePkgConfig` setup hook](https://nixos.org/manual/nixpkgs/stable/#validatepkgconfig), for packages that provide pkg-config modules.
- The `defaultPkgConfigPackages` package set: a set of aliases, named after the modules they provide. This is meant to be used by language-to-nix integrations. Hand-written packages should use the normal Nixpkgs attribute name instead.
## Writing packages providing pkg-config modules
Packages should set `meta.pkgConfigProvides` with the list of package config modules they provide.
They should also use `testers.testMetaPkgConfig` to check that the final built package matches that list.
Additionally, the [`validatePkgConfig` setup hook](https://nixos.org/manual/nixpkgs/stable/#validatepkgconfig), will do extra checks on to-be-installed pkg-config modules.
A good example of all these things is zlib:
```
{ pkg-config, testers, ... }:
stdenv.mkDerivation (finalAttrs: {
...
nativeBuildInputs = [ pkg-config validatePkgConfig ];
passthru.tests.pkg-config = testers.testMetaPkgConfig finalAttrs.finalPackage;
meta = {
...
pkgConfigModules = [ "zlib" ];
};
})
```
## Accessing packages via pkg-config module name
### Within Nixpkgs
A [setup hook](#setup-hook-pkg-config) is bundled in the `pkg-config` package to bring a derivation's declared build inputs into the environment.
This will populate environment variables like `PKG_CONFIG_PATH`, `PKG_CONFIG_PATH_FOR_BUILD`, and `PKG_CONFIG_PATH_HOST` based on:
- how `pkg-config` itself is depended upon
- how other dependencies are depended upon
For more details see the section on [specifying dependencies in general](#ssec-stdenv-dependencies).
Normal pkg-config commands to look up dependencies by name will then work with those environment variables defined by the hook.
### Externally
The `defaultPkgConfigPackages` package set is a set of aliases, named after the modules they provide.
This is meant to be used by language-to-nix integrations.
Hand-written packages should use the normal Nixpkgs attribute name instead.