929423476e
This is useful for frameworks (such as flake-parts) to avoid unnecessary evaluation. See discussion here: https://github.com/hercules-ci/flake-parts/issues/288#issuecomment-2912459614 While digging into this, I discovered that `nix fmt` already handles `null` formatters identically to undefined formatters. I added a couple of tests to demonstrate this behavior. `nix flake show` needs some reworking to avoid crashing with a "error: expected a derivation" when it encounters a `null` formatter or package. My changes here avoid the crash, but has some cosmetic issues, which is why I've labeled this PR as a draft. Cosmetic issues =============== With the following `flake.nix`: ```nix { outputs = _: { packages.x86_64-linux.default = null; }; } ``` `nix flake show` shows a weird empty system: ``` $ nix flake show path:/tmp/tmp.uL0iGuNwXB?lastModified=1748472558&narHash=sha256-tC%2BhdXAyoeFvWHNllJbois8X%2B7wpZ6CJzEzbcaGQxtM%3D └───packages └───x86_64-linux ``` Similarly, `nix flake show --json` includes an empty object: ``` $ nix flake show --json { "packages": { "x86_64-linux": { "default": null } } } ``` `nix build` crashes: ``` $ nix build .#default error: expected flake output attribute 'packages.x86_64-linux.default' to be a derivation or path but found null: null ``` |
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| .github | ||
| contrib | ||
| doc/manual | ||
| maintainers | ||
| misc | ||
| nix-meson-build-support | ||
| packaging | ||
| scripts | ||
| src | ||
| tests | ||
| .clang-format | ||
| .clang-tidy | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .gitignore | ||
| .mergify.yml | ||
| .shellcheckrc | ||
| .version | ||
| CITATION.cff | ||
| CONTRIBUTING.md | ||
| COPYING | ||
| default.nix | ||
| docker.nix | ||
| flake.lock | ||
| flake.nix | ||
| HACKING.md | ||
| meson.build | ||
| meson.options | ||
| README.md | ||
| shell.nix | ||
Nix
Nix is a powerful package manager for Linux and other Unix systems that makes package management reliable and reproducible. Please refer to the Nix manual for more details.
Installation and first steps
Visit nix.dev for installation instructions and beginner tutorials.
Full reference documentation can be found in the Nix manual.
Building and developing
Follow instructions in the Nix reference manual to set up a development environment and build Nix from source.
Contributing
Check the contributing guide if you want to get involved with developing Nix.
Additional resources
Nix was created by Eelco Dolstra and developed as the subject of his PhD thesis The Purely Functional Software Deployment Model, published 2006. Today, a world-wide developer community contributes to Nix and the ecosystem that has grown around it.
- The Nix, Nixpkgs, NixOS Community on nixos.org
- Official documentation on nix.dev
- Nixpkgs is the largest, most up-to-date free software repository in the world
- NixOS is a Linux distribution that can be configured fully declaratively
- Discourse
- Matrix: #users:nixos.org for user support and #nix-dev:nixos.org for development
License
Nix is released under the LGPL v2.1.