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diff --git a/nixos/doc/manual/development/meta-attributes.section.md b/nixos/doc/manual/development/meta-attributes.section.md new file mode 100644 index 00000000000..946c08efd0a --- /dev/null +++ b/nixos/doc/manual/development/meta-attributes.section.md @@ -0,0 +1,66 @@ +# Meta Attributes {#sec-meta-attributes} + +Like Nix packages, NixOS modules can declare meta-attributes to provide +extra information. Module meta attributes are defined in the `meta.nix` +special module. + +`meta` is a top level attribute like `options` and `config`. Available +meta-attributes are `maintainers`, `doc`, and `buildDocsInSandbox`. + +Each of the meta-attributes must be defined at most once per module +file. + +```nix +{ config, lib, pkgs, ... }: +{ + options = { + ... + }; + + config = { + ... + }; + + meta = { + maintainers = with lib.maintainers; [ ericsagnes ]; + doc = ./default.xml; + buildDocsInSandbox = true; + }; +} +``` + +- `maintainers` contains a list of the module maintainers. + +- `doc` points to a valid DocBook file containing the module + documentation. Its contents is automatically added to + [](#ch-configuration). Changes to a module documentation have to + be checked to not break building the NixOS manual: + + ```ShellSession + $ nix-build nixos/release.nix -A manual.x86_64-linux + ``` + +- `buildDocsInSandbox` indicates whether the option documentation for the + module can be built in a derivation sandbox. This option is currently only + honored for modules shipped by nixpkgs. User modules and modules taken from + `NIXOS_EXTRA_MODULE_PATH` are always built outside of the sandbox, as has + been the case in previous releases. + + Building NixOS option documentation in a sandbox allows caching of the built + documentation, which greatly decreases the amount of time needed to evaluate + a system configuration that has NixOS documentation enabled. The sandbox also + restricts which attributes may be referenced by documentation attributes + (such as option descriptions) to the `options` and `lib` module arguments and + the `pkgs.formats` attribute of the `pkgs` argument, `config` and the rest of + `pkgs` are disallowed and will cause doc build failures when used. This + restriction is necessary because we cannot reproduce the full nixpkgs + instantiation with configuration and overlays from a system configuration + inside the sandbox. The `options` argument only includes options of modules + that are also built inside the sandbox, referencing an option of a module + that isn't built in the sandbox is also forbidden. + + The default is `true` and should usually not be changed; set it to `false` + only if the module requires access to `pkgs` in its documentation (e.g. + because it loads information from a linked package to build an option type) + or if its documentation depends on other modules that also aren't sandboxed + (e.g. by using types defined in the other module). |