|
| 1 | +Cross-referencing with Sphinx |
| 2 | +============================= |
| 3 | + |
| 4 | +When writing documentation you often need to link to other pages of your documentation, |
| 5 | +other sections of the current page, or sections from other pages. |
| 6 | + |
| 7 | +.. _target to paragraph: |
| 8 | + |
| 9 | +An easy way is just to use the raw URL that Sphinx generates for each page/section. |
| 10 | +This works, but it has some disadvantages: |
| 11 | + |
| 12 | +- Links can change, so they are hard to maintain. |
| 13 | +- Links can be verbose and hard to read, so it is unclear what page/section they are linking to. |
| 14 | +- There is no easy way to link to specific sections like paragraphs, figures, or code blocks. |
| 15 | +- URL links only work for the html version of your documentation. |
| 16 | + |
| 17 | +reStructuredText has a built-in way to linking to elements, |
| 18 | +and Sphinx extends this to make it even more powerful! |
| 19 | +Some advantages of using reStructuredText's references: |
| 20 | + |
| 21 | +- Use a human-readable name of your choice, instead of a URL. |
| 22 | +- Portable between formats: html, PDF, ePub. |
| 23 | +- Sphinx will warn you of invalid references. |
| 24 | +- You can cross reference more than just pages and section headers. |
| 25 | + |
| 26 | +This page describes some best-practices for cross-referencing with Sphinx. |
| 27 | + |
| 28 | +.. contents:: Table of contents |
| 29 | + :local: |
| 30 | + :backlinks: none |
| 31 | + :depth: 3 |
| 32 | + |
| 33 | +Getting started |
| 34 | +--------------- |
| 35 | + |
| 36 | +.. _My target: |
| 37 | + |
| 38 | +Explicit targets |
| 39 | +~~~~~~~~~~~~~~~~ |
| 40 | + |
| 41 | +.. note:: |
| 42 | + |
| 43 | + If you are not familiar with reStructuredText, |
| 44 | + check :doc:`sphinx:usage/restructuredtext/basics` for a quick introduction. |
| 45 | + |
| 46 | +Cross referencing in Sphinx uses two components, **references** and **targets**. |
| 47 | + |
| 48 | +- **references** are pointers in your documentation to other parts of your documentation. |
| 49 | +- **targets** are where the references can point to. |
| 50 | + |
| 51 | +You can manually create a *target* in any location of your documentation, allowing |
| 52 | +you to *reference* it from other pages. These are called **explicit targets**. |
| 53 | + |
| 54 | +For example, one way of creating an explicit target for a section is: |
| 55 | + |
| 56 | +.. code-block:: rst |
| 57 | +
|
| 58 | + .. _My target: |
| 59 | +
|
| 60 | + Explicit targets |
| 61 | + ~~~~~~~~~~~~~~~~ |
| 62 | +
|
| 63 | +Then we can reference the section using ```My target`_``, |
| 64 | +that will be rendered as `My target`_. |
| 65 | + |
| 66 | +You can also add explicit targets before paragraphs (or any other part of a page). |
| 67 | + |
| 68 | +Another example, here we add a target to a paragraph: |
| 69 | + |
| 70 | +.. code-block:: rst |
| 71 | +
|
| 72 | + .. _target to paragraph: |
| 73 | +
|
| 74 | + An easy way is just to use the final link of the page/section. |
| 75 | + This works, but it has some disadvantages: |
| 76 | +
|
| 77 | +Then we can reference it using ```target to paragraph`_``, |
| 78 | +that will be rendered as: `target to paragraph`_. |
| 79 | + |
| 80 | +The reference displays the name of the target by default, |
| 81 | +but we can use any text you want. For example: |
| 82 | +```my custom text <target to paragraph>`_``, |
| 83 | +that will be rendered as: `my custom text <target to paragraph>`_. |
| 84 | + |
| 85 | +We can also create _`in-line targets` within an element on your page, |
| 86 | +allowing you to, for example, reference text *within* a paragraph. |
| 87 | + |
| 88 | +For example, an in-line target inside a paragraph: |
| 89 | + |
| 90 | +.. code-block:: rst |
| 91 | +
|
| 92 | + We can also create _`in-line targets` within an element on your page, |
| 93 | + allowing you to, for example, reference text *within* a paragraph. |
| 94 | +
|
| 95 | +Then we can reference it using ```in-line targets`_``, |
| 96 | +that will be rendered as: `in-line targets`_. |
| 97 | + |
| 98 | +Implicit targets |
| 99 | +~~~~~~~~~~~~~~~~ |
| 100 | + |
| 101 | +You may also reference sections by name without explicitly giving them one by |
| 102 | +using *implicit targets*. |
| 103 | + |
| 104 | +When we create a section, |
| 105 | +reStructuredText will create a target with the title as the name. |
| 106 | +For example, to reference the previous section we can use ```Explicit targets`_``, |
| 107 | +that will be rendered as: `Explicit targets`_. |
| 108 | + |
| 109 | +.. note:: |
| 110 | + |
| 111 | + `Footnotes <https://docutils.sourceforge.io/docs/user/rst/quickref.html#footnotes>`_ and |
| 112 | + `citations <https://docutils.sourceforge.io/docs/user/rst/quickref.html#citations>`_ |
| 113 | + also create implicit targets. |
| 114 | + |
| 115 | +Cross-referencing using roles |
| 116 | +----------------------------- |
| 117 | + |
| 118 | +All targets that we have seen so far can be referenced only from the same page. |
| 119 | +Sphinx provides some roles that allows us to reference any explicit target from any page. |
| 120 | + |
| 121 | +.. note:: |
| 122 | + |
| 123 | + Since Sphinx will make all explicit targets available globally, |
| 124 | + all targets must be unique. |
| 125 | + |
| 126 | +You can see the complete list of cross-referencing roles at :ref:`sphinx:xref-syntax`. |
| 127 | +Next, we will explore the most common ones. |
| 128 | + |
| 129 | +The ref role |
| 130 | +~~~~~~~~~~~~ |
| 131 | + |
| 132 | +The ``ref`` role can be used to reference any explicit target. For example: |
| 133 | + |
| 134 | +.. code-block:: rst |
| 135 | +
|
| 136 | + - :ref:`my target`. |
| 137 | + - :ref:`Target to paragraph <target to paragraph>`. |
| 138 | + - :ref:`Target inside a paragraph <in-line targets>`. |
| 139 | +
|
| 140 | +That will be rendered as: |
| 141 | + |
| 142 | +- :ref:`my target`. |
| 143 | +- :ref:`Target to paragraph <target to paragraph>`. |
| 144 | +- :ref:`Target inside a paragraph <in-line targets>`. |
| 145 | + |
| 146 | +The ``ref`` role also allow us to reference code blocks: |
| 147 | + |
| 148 | +.. code-block:: rst |
| 149 | +
|
| 150 | + .. _target to code: |
| 151 | +
|
| 152 | + .. code-block:: python |
| 153 | +
|
| 154 | + # Add the extension |
| 155 | + extensions = [ |
| 156 | + 'sphinx.ext.autosectionlabel', |
| 157 | + ] |
| 158 | +
|
| 159 | + # Make sure the target is unique |
| 160 | + autosectionlabel_prefix_document = True |
| 161 | +
|
| 162 | +We can reference it using ``:ref:`code <target to code>```, |
| 163 | +that will be rendered as: :ref:`code <target to code>`. |
| 164 | + |
| 165 | +The doc role |
| 166 | +~~~~~~~~~~~~ |
| 167 | + |
| 168 | +The `doc` role allows us to link to a page instead of just a section. |
| 169 | +The target name can be relative to the page where the role exists, or relative |
| 170 | +to your documentation's root folder (in both cases, you should omit the extension). |
| 171 | + |
| 172 | +For example, to link to a page in the same directory as this one we can use: |
| 173 | + |
| 174 | +.. code-block:: rst |
| 175 | +
|
| 176 | + - :doc:`intersphinx` |
| 177 | + - :doc:`/guides/intersphinx` |
| 178 | + - :doc:`Custom title </guides/intersphinx>` |
| 179 | +
|
| 180 | +That will be rendered as: |
| 181 | + |
| 182 | +- :doc:`intersphinx` |
| 183 | +- :doc:`/guides/intersphinx` |
| 184 | +- :doc:`Custom title </guides/intersphinx>` |
| 185 | + |
| 186 | +.. tip:: |
| 187 | + |
| 188 | + Using paths relative to your documentation root is recommended, |
| 189 | + so we avoid changing the target name if the page is moved. |
| 190 | + |
| 191 | +The numref role |
| 192 | +~~~~~~~~~~~~~~~ |
| 193 | + |
| 194 | +The ``numref`` role is used to reference **numbered** elements of your documentation. |
| 195 | +For example, tables and images. |
| 196 | + |
| 197 | +To activate numbered references, add this to your ``conf.py`` file: |
| 198 | + |
| 199 | +.. code-block:: python |
| 200 | +
|
| 201 | + # Enable numref |
| 202 | + numfig = True |
| 203 | +
|
| 204 | +Next, ensure that an object you would like to reference has an explicit target. |
| 205 | + |
| 206 | +For example, we can create a target for the next image: |
| 207 | + |
| 208 | +.. _target to image: |
| 209 | + |
| 210 | +.. figure:: /img/logo.png |
| 211 | + :alt: Logo |
| 212 | + :align: center |
| 213 | + :width: 240px |
| 214 | + |
| 215 | + Link me! |
| 216 | + |
| 217 | +.. code-block:: rst |
| 218 | +
|
| 219 | + .. _target to image: |
| 220 | +
|
| 221 | + .. figure:: /img/logo.png |
| 222 | + :alt: Logo |
| 223 | + :align: center |
| 224 | + :width: 240px |
| 225 | +
|
| 226 | + Link me! |
| 227 | +
|
| 228 | +Finally, reference it using ``:numref:`target to image```, |
| 229 | +that will be rendered as :numref:`target to image`. |
| 230 | +Sphinx will enumerate the image automatically. |
| 231 | + |
| 232 | +Automatically label sections |
| 233 | +---------------------------- |
| 234 | + |
| 235 | +Manually adding an explicit target to each section and making sure is unique |
| 236 | +is a big task! Fortunately, Sphinx includes an extension to help us with that problem, |
| 237 | +:doc:`autosectionlabel <sphinx:usage/extensions/autosectionlabel>`. |
| 238 | + |
| 239 | +To activate the ``autosectionlabel`` extension, add this to your ``conf.py`` file: |
| 240 | + |
| 241 | +.. _target to code: |
| 242 | + |
| 243 | +.. code-block:: python |
| 244 | +
|
| 245 | + # Add the extension |
| 246 | + extensions = [ |
| 247 | + 'sphinx.ext.autosectionlabel', |
| 248 | + ] |
| 249 | +
|
| 250 | + # Make sure the target is unique |
| 251 | + autosectionlabel_prefix_document = True |
| 252 | +
|
| 253 | +Sphinx will create explicit targets for all your sections, |
| 254 | +the name of target has the form ``{path/to/page}:{title-of-section}``. |
| 255 | + |
| 256 | +For example, we can reference the previous section using: |
| 257 | + |
| 258 | +.. code-block:: rst |
| 259 | +
|
| 260 | + - :ref:`guides/cross-referencing-with-sphinx:explicit targets`. |
| 261 | + - :ref:`Custom title <guides/cross-referencing-with-sphinx:explicit targets>`. |
| 262 | +
|
| 263 | +That will be rendered as: |
| 264 | + |
| 265 | +- :ref:`guides/cross-referencing-with-sphinx:explicit targets`. |
| 266 | +- :ref:`Custom title <guides/cross-referencing-with-sphinx:explicit targets>`. |
| 267 | + |
| 268 | +Invalid targets |
| 269 | +--------------- |
| 270 | + |
| 271 | +If we reference an invalid or undefined target Sphinx will warn us. |
| 272 | +You can use the :option:`-W <sphinx:sphinx-build.-W>` option when building your docs |
| 273 | +to fail the build if there are any invalid references. |
| 274 | +On Read the Docs you can use the :ref:`config-file/v2:sphinx.fail_on_warning` option. |
| 275 | + |
| 276 | +Finding the reference name |
| 277 | +-------------------------- |
| 278 | + |
| 279 | +When you build your documentation, Sphinx will generate an inventory of all |
| 280 | +explicit and implicit links called ``objects.inv``. You can list all of these targets to |
| 281 | +explore what is available for you to reference. |
| 282 | + |
| 283 | +List all targets for built documentation with: |
| 284 | + |
| 285 | +.. prompt:: bash |
| 286 | + |
| 287 | + python -m sphinx.ext.intersphinx <link> |
| 288 | + |
| 289 | +Where ``<link>`` is either a URL or a local path that points to your inventory file |
| 290 | +(usually in ``_build/html/objects.inv``). |
| 291 | +For example, to see all targets from the Read the Docs documentation: |
| 292 | + |
| 293 | +.. prompt:: bash |
| 294 | + |
| 295 | + python -m sphinx.ext.intersphinx https://docs.readthedocs.io/en/stable/objects.inv |
| 296 | + |
| 297 | +Cross-referencing targets in other documentation sites |
| 298 | +------------------------------------------------------ |
| 299 | + |
| 300 | +You can reference to docs outside your project too! See :doc:`/guides/intersphinx`. |
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