77 lines
3 KiB
Markdown
77 lines
3 KiB
Markdown
# Lix NixOS module
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See the [official installation guide][install-guide] for details on usage of
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release versions.
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[install-guide]: https://lix.systems/install/
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See the [beta guide][beta-guide] for a setup guide on how to use HEAD:
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[beta-guide]: https://wiki.lix.systems/link/1
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## What does this do?
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This is an overlay wrapped in a NixOS module that will replace CppNix with Lix
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in nixpkgs. This is useful so that `nixos-rebuild`, `nix-direnv` and similar
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will use Lix.
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Optionally, it can build Lix from source.
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## Versioning with Lix
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The version of this overlay should match the major Lix version, *and* if
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running HEAD, it should be the latest available version of the overlay.
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Breaking changes to the overlay are shamelessly done on HEAD.
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The version of Lix pinned in this flake's `flake.lock` is a version of Lix
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that is expected to work, however if running HEAD, it can be assumed to work
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with HEAD as well if both `lix-nixos-module` and `lix` are the latest version.
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## Common pitfalls
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Various flake frameworks such as flake-parts and snowfall (and possibly Colmena
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in the future if they do a similar optimization) manage overlays separately
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from NixOS, since they provide `pkgs` pre-imported to NixOS. This saves a
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couple of seconds of evaluation time and resources, but it means that the NixOS
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option `nixpkgs.overlays` **is completely ignored** on these frameworks.
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If you are using such a framework, add `overlays.default` to the overlays list
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for said framework.
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## Flake structure and usage
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The flake here has two inputs of note:
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- `nixpkgs`, *which is unused for most people*. It is purely used for `checks`
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in developing `lix-nixos-module` itself.
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The installation instructions make it `follows` to make `flake.lock` less
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confusing, but it is nonetheless unused.
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- `lix`, which determines the version of Lix to do source builds for, if doing
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source builds.
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These are the most relevant outputs for most people:
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- `nixosModules.lixFromNixpkgs` - uses Lix from nixpkgs and installs the
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overlay to use Lix on a NixOS system. This is only useful for a stable
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version of Lix, and cannot be used for running HEAD.
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- `nixosModules.default` - uses Lix from source and installs the overlay to use
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Lix on a NixOS system.
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- `overlays.lixFromNixpkgs` - overlay to use Lix from nixpkgs in place of Nix.
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- `overlays.default` - overlay to use Lix from source in place of Nix.
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## Non-flake usage
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Import `module.nix` or `overlay.nix` as desired, with the arguments `lix`
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(derivation-like attribute set with the Lix sources, or `null` to use Lix from
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nixpkgs) and `versionSuffix` (optional string).
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It's desirable to also include a `versionSuffix` like the following while
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building HEAD from source, to have `nix --version` include date and commit
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information. To get such metadata, it depends on which pinning system is in
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use, but `builtins.fetchGit` will provide the necessary metadata for the
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following to work:
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```
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versionSuffix = "pre${builtins.substring 0 8 lix.lastModifiedDate}-${lix.shortRev or lix.dirtyShortRev}";
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```
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