lib.mkPackageVariants: init; openssl: migrate to mkPackageVariants by qweered · Pull Request #496617 · NixOS/nixpkgs

qweered · 2026-03-04T17:17:06Z

Adds lib.mkPackageVariants to standardize multi-version package management in nixpkgs. Currently, packages like openssl, perl, etc. each reinvent their own variant handling — this provides a shared abstraction for it. Extensive tests added to lib/test/customisation.nix

Inspired by corepkgs' mkManyVariants, but adapted for nixpkgs:

	corepkgs `mkManyVariants`	nixpkgs `mkPackageVariants`
`callPackage`	Uses internal `callFromScope`	Caller-provided `callPackage`, pre-bound via `splice.nix` (same pattern as `callPackage` itself)
`allowAliases`	Reads from `config` directly	Explicit parameter, defaults to `config.allowAliases` in the splice binding
Return value	`defaultPackage.override`	`defaultPackage` directly (override is already available via `callPackage`/`makeOverridable`)
Feature variants	Not supported	Per-variant `overrideArgs` allows feature variants (e.g., `oqs`, `legacy`) that share version metadata but change build arguments
File detection	Explicit paths required	Auto-detects `variants.nix` and `generic.nix` in caller's directory via `unsafeGetAttrPos`

The generic builder follows a curried pattern — first receives variant-specific args (version, hash, patches, plus helpers like packageOlder/packageAtLeast), then package args resolved by callPackage. All variants are accessible via passthru (e.g., openssl.v1_1, openssl.v3_6, openssl.oqs), and pkg.override { ... } flows through to the generic builder without per-package boilerplate.

I migrated openssl as a proof-of-concept to verify everything works end-to-end, including by-name compatibility. The old monolithic default.nix is split into generic.nix (curried builder), variants.nix (version metadata), and a thin package.nix wrapper. openssl_oqs and openssl_legacy are also migrated from inline .override calls to proper variants. All backward-compat aliases are preserved.

Things done

RossComputerGuy

The approach so far seems reasonable, only have this nit so far.

lib/customisation.nix

qweered · 2026-03-04T17:39:53Z

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Command: nixpkgs-review pr 496617
Commit: 6653d83ae8968aaa3a4dd937d6944d7d73ec47cf

`x86_64-linux`

⏩ 2 packages blacklisted:

nixos-install-tools
tests.nixos-functions.nixos-test

✅ 4 packages built:

extra-container
nixos-container
nixpkgs-manual
tests.lib-tests

quantenzitrone · 2026-03-05T00:01:23Z

lib/customisation.nix

+        pkg.overrideAttrs (o: {
+          passthru =
+            o.passthru or { }
+            // mkVariantPassthru variantArgs
+            // {
+              inherit variantArgs;
+            };
+        });


How do we tell the nixpkgs search which attributes should be shown?
How do we tell hydra where all the package variants are located that need to be evaluated?

As far as I know this is currently done through recurseForDerivations = true;, so all attribute sets with that attribute are also searched for derivations.

This does not work for attributes in passthru. We can't search every package for derivations.

Yeah, derivations inside derivations are a non‐starter without several changes outside of Nixpkgs. nix search and nix-env can’t handle them either; it’s baked into the codebase.

While writing down the new version of my RFC 197 I thought we could maybe make all versioned packages package sets like we currently do for nix with nixVersions.
If we do that it would be consistent to also have versioned package sets be in a package-set-set like currently for ocamlPackages with ocaml-ng and lixPackages with lixPackageSets.

@Args

Add `lib.mkPackageVariants`, a utility for managing multiple variants (versions or feature variants) of a single package with a shared generic builder. The function is curried in three stages: 1. Scope args (callPackage, allowAliases) — pre-bound in splice.nix 2. Override args — captured via @Args, forwarded to the generic builder 3. Package config — variant selection, paths, aliases The generic builder follows a curried pattern: variantArgs -> packageArgs -> derivation-attrs Each variant's passthru includes references to all other variants, enabling access patterns like `pkg.v1_1`, `pkg.v3`, etc.

Preparatory rename for the mkPackageVariants migration to preserve git history

Refactor openssl to use the new `lib.mkPackageVariants` utility: - generic.nix: Convert from monolithic callPackages pattern to curried builder (variantArgs -> packageArgs -> derivation-attrs). Replace lib.versionOlder/AtLeast with injected packageOlder/packageAtLeast. Move withDocs and extraMeta logic into the builder using version checks instead of per-variant metadata. - variants.nix: Extract version metadata (version, hash, patches) into a dedicated file resolved via callPackage. - default.nix: Thin mkPackageVariants entry point that only specifies the default variant selector. - all-packages.nix: Simplify openssl wiring. Old names (openssl_1_1, openssl_3, openssl_3_6) become aliases to openssl.v1_1 etc.

Move openssl from pkgs/development/libraries/openssl to pkgs/by-name/op/openssl, renaming default.nix to package.nix per by-name convention.

qweered changed the title ~~lib.mkPackageVariants: init, migrate openssl~~ lib.mkPackageVariants: init, migrate openssl to mkPackageVariant Mar 4, 2026

nixpkgs-ci bot requested review from a team, Ericson2314, alyssais, hsjobeki, infinisil and thillux March 4, 2026 17:26

github-project-automation bot added this to Nixpkgs Lib Mar 4, 2026

qweered force-pushed the lib/mkPackageVariants branch 2 times, most recently from 96ec04d to 6653d83 Compare March 4, 2026 17:30

RossComputerGuy reviewed Mar 4, 2026

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nixpkgs-ci bot removed the 2.status: merge conflict This PR has merge conflicts with the target branch label Mar 4, 2026

qweered mentioned this pull request Mar 4, 2026

[RFC 0197] package sets by-name NixOS/rfcs#197

Draft

qweered changed the title ~~lib.mkPackageVariants: init, migrate openssl to mkPackageVariant~~ lib.mkPackageVariants: init, openssl: migrate to mkPackageVariants Mar 4, 2026

qweered force-pushed the lib/mkPackageVariants branch 2 times, most recently from b3c1085 to 912f142 Compare March 4, 2026 18:40

quantenzitrone reviewed Mar 5, 2026

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nixpkgs-ci bot added the 2.status: merge conflict This PR has merge conflicts with the target branch label Mar 18, 2026

qweered marked this pull request as draft March 23, 2026 16:14

qweered changed the title ~~lib.mkPackageVariants: init, openssl: migrate to mkPackageVariants~~ lib.mkPackageVariants: init; openssl: migrate to mkPackageVariants Mar 23, 2026

qweered added 2 commits March 23, 2026 18:16

openssl: rename default.nix to generic.nix

d6ec561

Preparatory rename for the mkPackageVariants migration to preserve git history

qweered force-pushed the lib/mkPackageVariants branch from 912f142 to cbd10b6 Compare March 23, 2026 18:54

nixpkgs-ci bot removed the 2.status: merge conflict This PR has merge conflicts with the target branch label Mar 23, 2026

qweered force-pushed the lib/mkPackageVariants branch from cbd10b6 to bf731f2 Compare March 23, 2026 20:01

qweered added 3 commits March 24, 2026 18:29

openssl: move to pkgs/by-name

e843437

Move openssl from pkgs/development/libraries/openssl to pkgs/by-name/op/openssl, renaming default.nix to package.nix per by-name convention.

openssl_oqs, openssl_legacy: migrate to mkPackageVariants

db6f0b0

qweered force-pushed the lib/mkPackageVariants branch from bf731f2 to db6f0b0 Compare March 24, 2026 16:29

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lib.mkPackageVariants: init; openssl: migrate to mkPackageVariants#496617

lib.mkPackageVariants: init; openssl: migrate to mkPackageVariants#496617
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