nixpkgs/doc/contributing/contributing-to-documentation.chapter.md
Jan Tojnar 6ecc641d08
doc: prepare for commonmark
We are still using Pandoc’s Markdown parser, which differs from CommonMark spec slightly.

Notably:
- Line breaks in lists behave differently.
- Admonitions do not support the simpler syntax https://github.com/jgm/commonmark-hs/issues/75
- The auto_identifiers uses a different algorithm – I made the previous ones explicit.
- Languages (classes) of code blocks cannot contain whitespace so we have to use “pycon” alias instead of Python “console” as GitHub’s linguist

While at it, I also fixed the following issues:
- ShellSesssion was used
- Removed some pointless docbook tags.
2021-06-07 06:34:59 +02:00

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# Contributing to this documentation {#chap-contributing}
The sources of the Nixpkgs manual are in the [doc](https://github.com/NixOS/nixpkgs/tree/master/doc) subdirectory of the Nixpkgs repository. The manual is still partially written in DocBook but it is progressively being converted to [Markdown](#sec-contributing-markup).
You can quickly check your edits with `make`:
```ShellSession
$ cd /path/to/nixpkgs/doc
$ nix-shell
[nix-shell]$ make
```
If you experience problems, run `make debug` to help understand the docbook errors.
After making modifications to the manual, it's important to build it before committing. You can do that as follows:
```ShellSession
$ cd /path/to/nixpkgs/doc
$ nix-shell
[nix-shell]$ make clean
[nix-shell]$ nix-build .
```
If the build succeeds, the manual will be in `./result/share/doc/nixpkgs/manual.html`.
## Syntax {#sec-contributing-markup}
As per [RFC 0072](https://github.com/NixOS/rfcs/pull/72), all new documentation content should be written in [CommonMark](https://commonmark.org/) Markdown dialect.
Additionally, the following syntax extensions are currently used:
- []{#ssec-contributing-markup-anchors}
Explicitly defined **anchors** on headings, to allow linking to sections. These should be always used, to ensure the anchors can be linked even when the heading text changes, and to prevent conflicts between [automatically assigned identifiers](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/auto_identifiers.md).
It uses the widely compatible [header attributes](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/attributes.md) syntax:
```markdown
## Syntax {#sec-contributing-markup}
```
- []{#ssec-contributing-markup-anchors-inline}
**Inline anchors**, which allow linking arbitrary place in the text (e.g. individual list items, sentences…).
They are defined using a hybrid of the link syntax with the attributes syntax known from headings, called [bracketed spans](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/bracketed_spans.md):
```markdown
- []{#ssec-gnome-hooks-glib} `glib` setup hook will populate `GSETTINGS_SCHEMAS_PATH` and then `wrapGAppsHook` will prepend it to `XDG_DATA_DIRS`.
```
- []{#ssec-contributing-markup-admonitions}
**Admonitions**, set off from the text to bring attention to something.
It uses pandocs [fenced `div`s syntax](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/fenced_divs.md):
```markdown
::: {.warning}
This is a warning
:::
```
which renders as
> ::: {.warning}
> This is a warning.
> :::
The following are supported:
- [`caution`](https://tdg.docbook.org/tdg/5.0/caution.html)
- [`important`](https://tdg.docbook.org/tdg/5.0/important.html)
- [`note`](https://tdg.docbook.org/tdg/5.0/note.html)
- [`tip`](https://tdg.docbook.org/tdg/5.0/tip.html)
- [`warning`](https://tdg.docbook.org/tdg/5.0/warning.html)
- []{#ssec-contributing-markup-definition-lists}
[**Definition lists**](https://github.com/jgm/commonmark-hs/blob/master/commonmark-extensions/test/definition_lists.md), for defining a group of terms:
```markdown
pear
: green or yellow bulbous fruit
watermelon
: green fruit with red flesh
```
which renders as
> pear
> : green or yellow bulbous fruit
>
> watermelon
> : green fruit with red flesh
For contributing to the legacy parts, please see [DocBook: The Definitive Guide](https://tdg.docbook.org/) or the [DocBook rocks! primer](https://web.archive.org/web/20200816233747/https://docbook.rocks/).