pennae 0a6e6cf7e6 nixos/manual: render module chapters with nixos-render-docs

this converts meta.doc into an md pointer, not an xml pointer. since we
no longer need xml for manual chapters we can also remove support for
manual chapters from md-to-db.sh

since pandoc converts smart quotes to docbook quote elements and our
nixos-render-docs does not we lose this distinction in the rendered
output. that's probably not that bad, our stylesheet didn't make use of
this anyway (and pre-23.05 versions of the chapters didn't use quote
elements either).

also updates the nixpkgs manual to clarify that option docs support all
extensions (although it doesn't support headings at all, so heading
anchors don't work by extension).

2023-01-27 20:07:34 +01:00

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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.

{ config, lib, pkgs, ... }:
{
  options = {
    ...
  };

  config = {
    ...
  };

  meta = {
    maintainers = with lib.maintainers; [ ericsagnes ];
    doc = ./default.md;
    buildDocsInSandbox = true;
  };
}

maintainers contains a list of the module maintainers.
doc points to a valid Nixpkgs-flavored CommonMark file containing the module documentation. Its contents is automatically added to . Changes to a module documentation have to be checked to not break building the NixOS manual:
```
$ 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).

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Meta Attributes

2.7 KiB

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