searxng/docs/dev/reST.rst

.. _reST primer:

===========
reST primer
===========

.. sidebar:: KISS_ and readability_

   Instead of defining more and more roles, we at searx encourage our
   contributors to follow principles like KISS_ and readability_.

We at searx are using reStructuredText (aka reST_) markup for all kind of
documentation, with the builders from the Sphinx_ project a HTML output is
generated and deployed at :docs:`github.io <.>`.

The sources of Searx's documentation are located at :origin:`docs`.  Run
:ref:`make docs-live <make docs-live>` to build HTML while editing.

------

.. sidebar:: Further reading

   - Sphinx-Primer_
   - `Sphinx markup constructs`_
   - reST_, docutils_, `docutils FAQ`_
   - Sphinx_, `sphinx-doc FAQ`_
   - `sphinx config`_, doctree_
   - `sphinx cross references`_
   - linuxdoc_
   - intersphinx_
   - `Sphinx's autodoc`_
   - `Sphinx's Python domain`_, `Sphinx's C domain`_

.. contents:: Contents
   :depth: 3
   :local:
   :backlinks: entry

------

Sphinx_ and reST_ have their place in the python ecosystem.  Over that reST is
used in popular projects, e.g the Linux kernel documentation `[kernel doc]`_.

.. _[kernel doc]: https://www.kernel.org/doc/html/latest/doc-guide/sphinx.html

.. sidebar:: Content matters

   The readability_ of the reST sources has its value, therefore we recommend to
   make sparse usage of reST markup / .. content matters!

**reST** is a plaintext markup language, its markup is *mostly* intuitive and
you will not need to learn much to produce well formed articles with.  I use the
word *mostly*: like everything in live, reST has its advantages and
disadvantages, some markups feel a bit grumpy (especially if you are used to
other plaintext markups).

Soft skills
===========

Before going any deeper into the markup let's face on some **soft skills** a
trained author brings with, to reach a well feedback from readers:

- Documentation is dedicated to an audience and answers questions from the
  audience point of view.
- Don't detail things which are general knowledge from the audience point of
  view.
- Limit the subject, use cross links for any further reading.

To be more concrete what a *point of view* means.  In the (:origin:`docs`)
folder we have three sections (and the *blog* folder), each dedicate to a
different group of audience.

User's POV: :origin:`docs/user`
  A typical user knows about search engines and might have heard about
  meta crawlers and privacy.

Admin's POV: :origin:`docs/admin`
  A typical Admin knows about setting up services on a linux system, but he does
  not know all the pros and cons of a searx setup.

Developer's POV: :origin:`docs/dev`
  Depending on the readability_ of code, a typical developer is able to read and
  understand source code.  Describe what a item aims to do (e.g. a function),
  describe chronological order matters, describe it.  Name the *out-of-limits
  condition* and all the side effects a external developer will not know.

.. _reST inline markup:

Basic inline markup
===================

``*italics*`` -- *italics*
  one asterisk for emphasis

``**boldface**`` -- **boldface**
  two asterisks for strong emphasis and

````foo()```` -- ``foo()``
  backquotes for code samples and literals.

``\*foo is a pointer`` -- \*foo is a pointer
  If asterisks or backquotes appear in running text and could be confused with
  inline markup delimiters, they have to be escaped with a backslash (``\*foo is
  a pointer``).

.. _reST basic structure:

Basic article structure
=======================

The basic structure of an article makes use of heading adornments to markup
chapter, sections and subsections.

#. ``=`` with overline for document title
#. ``=`` for chapters
#. ``-`` for sections
#. ``~`` for subsections

.. _reST template:

.. admonition:: reST template
   :class: rst-example

   .. code:: reST

       .. _document title:

       ==============
       Document title
       ==============

       Lorem ipsum dolor sit amet, consectetur adipisici elit ..
       Further read :ref:`chapter title`.

       .. _chapter title:

       Chapters
       ========

       Ut enim ad minim veniam, quis nostrud exercitation ullamco
       laboris nisi ut aliquid ex ea commodi consequat ...

       Section
       -------

       lorem ..

       Subsection
       ~~~~~~~~~~

       lorem ..


Anchors & Links
===============

.. _reST anchor:

Anchors
-------

.. _ref role:
   https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#role-ref

To refer a point in the documentation a anchor is needed.  The :ref:`reST
template <reST template>` shows an example where a chapter titled *"Chapters"*
gets an anchor named ``chapter title``.  Another example from *this* document,
where the anchor named ``reST anchor``:

.. code:: reST

   .. _reST anchor:

   Anchors
   -------

   To refer a point in the documentation a anchor is needed ...

To refer anchors use the `ref role`_ markup:

.. code:: reST

   Visit chapter :ref:`reST anchor`.
   Or set hyperlink text manualy :ref:`foo bar <reST anchor>`.

.. admonition:: ``:ref:`` role
   :class: rst-example

   Visist chapter :ref:`reST anchor`
   Or set hyperlink text manualy :ref:`foo bar <reST anchor>`.

.. _reST ordinary ref:

link ordinary URL
-----------------

If you need to reference external URLs use *named* hyperlinks to maintain
readability of reST sources.  Here is a example taken from *this* article:

.. code:: reST

   .. _Sphinx Field Lists:
      https://www.sphinx-doc.org/en/master/usage/restructuredtext/field-lists.html

   With the *named* hyperlink `Sphinx Field Lists`_, the raw text is much more
   readable.

   And this shows the alternative (less readable) hyperlink markup `Sphinx Field
   Lists
   <https://www.sphinx-doc.org/en/master/usage/restructuredtext/field-lists.html>`__.

.. admonition:: Named hyperlink
   :class: rst-example

   With the *named* hyperlink `Sphinx Field Lists`_, the raw text is much more
   readable.

   And this shows the alternative (less readable) hyperlink markup `Sphinx Field
   Lists
   <https://www.sphinx-doc.org/en/master/usage/restructuredtext/field-lists.html>`__.


.. _reST smart ref:

smart references
----------------

With the power of sphinx.ext.extlinks_ and intersphinx_ referencing external
content becomes smart.

========================== ================================== ====================================
refer ...                  rendered example                   markup
========================== ================================== ====================================
:rst:role:`rfc`            :rfc:`822`                         ``:rfc:`822```
:rst:role:`pep`            :pep:`8`                           ``:pep:`8```
sphinx.ext.extlinks_
--------------------------------------------------------------------------------------------------
project's wiki article     :wiki:`Searx-instances`            ``:wiki:`Searx-instances```
to docs public URL         :docs:`dev/reST.html`              ``:docs:`dev/reST.html```
files & folders origin     :origin:`docs/dev/reST.rst`        ``:origin:`docs/dev/reST.rst```
pull request               :pull:`1756`                       ``:pull:`1756```
patch                      :patch:`af2cae6`                   ``:patch:`af2cae6```
PyPi package               :pypi:`searx`                      ``:pypi:`searx```
manual page man            :man:`bash`                        ``:man:`bash```
intersphinx_
--------------------------------------------------------------------------------------------------
external anchor            :ref:`python:and`                  ``:ref:`python:and```
external doc anchor        :doc:`jinja:templates`             ``:doc:`jinja:templates```
python code object         :py:obj:`datetime.datetime`        ``:py:obj:`datetime.datetime```
flask code object          :py:obj:`flask.Flask`              ``:py:obj:`flask.Flask```
========================== ================================== ====================================


Intersphinx is configured in :origin:`docs/conf.py`:

.. code:: python

    intersphinx_mapping = {
        "python": ("https://docs.python.org/3/", None),
        "flask": ("https://flask.palletsprojects.com/", None),
	"jinja": ("https://jinja.palletsprojects.com/", None),
        "linuxdoc" : ("https://return42.github.io/linuxdoc/", None),
        "sphinx" : ("https://www.sphinx-doc.org/en/master/", None),
    }


To list all anchors of the inventory (e.g. ``python``) use:

.. code:: sh

   $ python -m sphinx.ext.intersphinx https://docs.python.org/3/objects.inv


Roles
=====

A *custom interpreted text role* (:duref:`ref <roles>`) is an inline piece of
explicit markup.  It signifies that that the enclosed text should be interpreted
in a specific way.  The general syntax is ``:rolename:`content```.

========================== ================================== ====================================
role                       rendered example                   markup
========================== ================================== ====================================
:rst:role:`guilabel`       :guilabel:`&Cancel`                ``:guilabel:`&Cancel```
:rst:role:`kbd`            :kbd:`C-x C-f`                     ``:kbd:`C-x C-f```
:rst:role:`menuselection`  :menuselection:`Open --> File`     ``:menuselection:`Open --> File```
:rst:role:`download`       :download:`this file <reST.rst>`   ``:download:`this file <reST.rst>```
:rst:role:`math`           :math:`a^2 + b^2 = c^2`            ``:math:`a^2 + b^2 = c^2```
:rst:role:`ref`            :ref:`svg image example`           ``:ref:`svg image example```
:rst:role:`command`        :command:`ls -la`                  ``:command:`ls -la```
:durole:`emphasis`         :emphasis:`italic`                 ``:emphasis:`italic```
:durole:`strong`           :strong:`bold`                     ``:strong:`bold```
:durole:`literal`          :literal:`foo()`                   ``:literal:`foo()```
:durole:`subscript`        H\ :sub:`2`\ O                     ``H\ :sub:`2`\ O``
:durole:`superscript`      E = mc\ :sup:`2`                   ``E = mc\ :sup:`2```
:durole:`title-reference`  :title:`Time`                      ``:title:`Time```
========================== ================================== ====================================

Refer to `Sphinx Roles`_ for roles added by Sphinx.


Figures & Images
================

Searx's sphinx setup includes: :ref:`linuxdoc:kfigure`.  Scalable here means;
scalable in sense of the build process.  Normally in absence of a converter
tool, the build process will break.  From the authors POV it’s annoying to care
about the build process when handling with images, especially since he has no
access to the build process.  With :ref:`linuxdoc:kfigure` the build process
continues and scales output quality in dependence of installed image processors.

If you want to add an image, you should use the ``kernel-figure`` and
``kernel-image`` directives.  E.g. to insert a figure with a scalable image
format use SVG (:ref:`svg_image_example`):

.. code:: reST

   .. _svg image example:

   .. kernel-figure:: svg_image.svg
      :alt: simple SVG image

      SVG image example

.. _svg image example:

.. kernel-figure:: svg_image.svg
   :alt: simple SVG image

   SVG image example

DOT files (aka Graphviz)
------------------------

The kernel figure (and image) directive support **DOT** formated files, see

* DOT: http://graphviz.org/pdf/dotguide.pdf
* Graphviz: http://www.graphviz.org/content/dot-language

A simple example (:ref:`hello_dot_file`):

.. code:: reST

   .. kernel-figure:: hello.dot
      :alt: hello world

      DOT's hello world example

.. admonition:: hello.dot
   :class: rst-example

   .. kernel-figure:: hello.dot
      :alt: hello world

      DOT's hello world example

``kernel-render`` DOT
---------------------

Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the
``kernel-render`` directives.

.. code:: reST

   .. kernel-render:: DOT markup
      :alt: foobar digraph
      :caption: Embedded **DOT** (Graphviz) code

      digraph foo {
        "bar" -> "baz";
      }

How this will be rendered depends on the installed tools.  If Graphviz is
installed, you will see an vector image.  If not the raw markup is inserted as
*literal-block* (:ref:`hello_dot_render`).

.. admonition:: DOT markup
   :class: rst-example

   .. _hello_dot_render:

   .. kernel-render:: DOT
      :alt: foobar digraph
      :caption: Embedded **DOT** (Graphviz) code

      digraph foo {
        "bar" -> "baz";
      }

The *render* directive has all the options known from the *figure* directive,
plus option ``caption``.  If ``caption`` has a value, a *figure* node is
inserted. If not, a *image* node is inserted. A ``caption`` is also needed, if
you want to refer it (:ref:`hello_svg_render`).


``kernel-render`` SVG
---------------------

.. code:: reST

   .. kernel-render:: SVG markup
      :caption: Embedded **SVG** markup
      :alt: so-nw-arrow
..

   .. code:: xml

      <?xml version="1.0" encoding="UTF-8"?>
      <svg xmlns="http://www.w3.org/2000/svg"
        version="1.1" baseProfile="full" width="70px" height="40px" viewBox="0 0 700 400">
      <line x1="180" y1="370" x2="500" y2="50" stroke="black" stroke-width="15px"/>
      <polygon points="585 0 525 25 585 50" transform="rotate(135 525 25)"/>
      </svg>

.. admonition:: SVG markup
   :class: rst-example

   .. _hello_svg_render:

   .. kernel-render:: SVG
      :caption: Embedded **SVG** markup
      :alt: so-nw-arrow

      <?xml version="1.0" encoding="UTF-8"?>
      <svg xmlns="http://www.w3.org/2000/svg"
        version="1.1" baseProfile="full" width="70px" height="40px" viewBox="0 0 700 400">
      <line x1="180" y1="370" x2="500" y2="50" stroke="black" stroke-width="15px"/>
      <polygon points="585 0 525 25 585 50" transform="rotate(135 525 25)"/>
      </svg>


.. _reST lists:

List markups
============

Bullet list
-----------

List markup (:duref:`ref <bullet-lists>`) is simple:

.. code:: reST

   - This is a bulleted list.

     1. Nested lists are possible, but be aware that they must be separated from
        the parent list items by blank line
     2. Second item of nested list

   - It has two items, the second
     item uses two lines.

   #. This is a numbered list.
   #. It has two items too.

.. admonition:: bullet list
   :class: rst-example

   - This is a bulleted list.

     1. Nested lists are possible, but be aware that they must be separated from
        the parent list items by blank line
     2. Second item of nested list

   - It has two items, the second
     item uses two lines.

   #. This is a numbered list.
   #. It has two items too.


Definition list
---------------

.. sidebar:: definition term

   Note that the term cannot have more than one line of text.

Definition lists (:duref:`ref <definition-lists>`) are created as follows:

.. code:: reST

   term (up to a line of text)
      Definition of the term, which must be indented

      and can even consist of multiple paragraphs

   next term
      Description.

.. admonition:: definition list
   :class: rst-example

   term (up to a line of text)
      Definition of the term, which must be indented

      and can even consist of multiple paragraphs

   next term
      Description.


Quoted paragraphs
-----------------

Quoted paragraphs (:duref:`ref <block-quotes>`) are created by just indenting
them more than the surrounding paragraphs.  Line blocks (:duref:`ref
<line-blocks>`) are a way of preserving line breaks:

.. code:: reST

   normal paragraph ...
   lorem ipsum.

      Quoted paragraph ...
      lorem ipsum.

   | These lines are
   | broken exactly like in
   | the source file.


.. admonition:: Quoted paragraph and line block
   :class: rst-example

   normal paragraph ...
   lorem ipsum.

      Quoted paragraph ...
      lorem ipsum.

   | These lines are
   | broken exactly like in
   | the source file.


.. _reST field list:

Field Lists
-----------

.. _Sphinx Field Lists:
   https://www.sphinx-doc.org/en/master/usage/restructuredtext/field-lists.html

.. sidebar::  bibliographic fields

   First lines fields are bibliographic fields, see `Sphinx Field Lists`_.

Field lists are used as part of an extension syntax, such as options for
directives, or database-like records meant for further processing.  Field lists
are mappings from field names to field bodies.  They marked up like this:

.. code:: reST

   :fieldname: Field content
   :foo:       first paragraph in field foo

	       second paragraph in field foo

   :bar:       Field content

.. admonition:: Field List
   :class: rst-example

   :fieldname: Field content
   :foo:       first paragraph in field foo

	       second paragraph in field foo

   :bar:       Field content


They are commonly used in Python documentation:

.. code:: python

   def my_function(my_arg, my_other_arg):
       """A function just for me.

       :param my_arg: The first of my arguments.
       :param my_other_arg: The second of my arguments.

       :returns: A message (just for me, of course).
       """

Further list blocks
-------------------

- field lists (:duref:`ref <field-lists>`, with caveats noted in
  :ref:`reST field list`)
- option lists (:duref:`ref <option-lists>`)
- quoted literal blocks (:duref:`ref <quoted-literal-blocks>`)
- doctest blocks (:duref:`ref <doctest-blocks>`)


.. _KISS: https://en.wikipedia.org/wiki/KISS_principle
.. _readability: https://docs.python-guide.org/writing/style/
.. _Sphinx-Primer:
    http://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html
.. _reST: https://docutils.sourceforge.io/rst.html
.. _Sphinx Roles:
    https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html
.. _Sphinx: http://www.sphinx-doc.org
.. _`sphinx-doc FAQ`: http://www.sphinx-doc.org/en/stable/faq.html
.. _Sphinx markup constructs:
    http://www.sphinx-doc.org/en/stable/markup/index.html
.. _`sphinx cross references`:
    http://www.sphinx-doc.org/en/stable/markup/inline.html#cross-referencing-arbitrary-locations
.. _sphinx.ext.extlinks:
    https://www.sphinx-doc.org/en/master/usage/extensions/extlinks.html
.. _intersphinx: http://www.sphinx-doc.org/en/stable/ext/intersphinx.html
.. _sphinx config: http://www.sphinx-doc.org/en/stable/config.html
.. _Sphinx's autodoc: http://www.sphinx-doc.org/en/stable/ext/autodoc.html
.. _Sphinx's Python domain:
    http://www.sphinx-doc.org/en/stable/domains.html#the-python-domain
.. _Sphinx's C domain:
   http://www.sphinx-doc.org/en/stable/domains.html#cross-referencing-c-constructs
.. _doctree:
    http://www.sphinx-doc.org/en/master/extdev/tutorial.html?highlight=doctree#build-phases
.. _docutils: http://docutils.sourceforge.net/docs/index.html
.. _docutils FAQ: http://docutils.sourceforge.net/FAQ.html
.. _linuxdoc: https://return42.github.io/linuxdoc