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<h1 id="code-style"><a class="header" href="#code-style">Code Style</a></h1>
<h2 id="formatting-tools"><a class="header" href="#formatting-tools">Formatting tools</a></h2>
<p>The Synapse codebase uses a number of code formatting tools in order to
quickly and automatically check for formatting (and sometimes logical)
errors in code.</p>
<p>The necessary tools are:</p>
<ul>
<li><a href="https://black.readthedocs.io/en/stable/">black</a>, a source code formatter;</li>
<li><a href="https://pycqa.github.io/isort/">isort</a>, which organises each file's imports;</li>
<li><a href="https://flake8.pycqa.org/en/latest/">flake8</a>, which can spot common errors; and</li>
<li><a href="https://mypy.readthedocs.io/en/stable/">mypy</a>, a type checker.</li>
</ul>
<p>Install them with:</p>
<pre><code class="language-sh">pip install -e ".[lint,mypy]"
</code></pre>
<p>The easiest way to run the lints is to invoke the linter script as follows.</p>
<pre><code class="language-sh">scripts-dev/lint.sh
</code></pre>
<p>It's worth noting that modern IDEs and text editors can run these tools
automatically on save. It may be worth looking into whether this
functionality is supported in your editor for a more convenient
development workflow. It is not, however, recommended to run <code>flake8</code> or <code>mypy</code>
on save as they take a while and can be very resource intensive.</p>
<h2 id="general-rules"><a class="header" href="#general-rules">General rules</a></h2>
<ul>
<li><strong>Naming</strong>:
<ul>
<li>Use <code>CamelCase</code> for class and type names</li>
<li>Use underscores for <code>function_names</code> and <code>variable_names</code>.</li>
</ul>
</li>
<li><strong>Docstrings</strong>: should follow the <a href="https://google.github.io/styleguide/pyguide.html#38-comments-and-docstrings">google code
style</a>.
See the
<a href="http://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html">examples</a>
in the sphinx documentation.</li>
<li><strong>Imports</strong>:
<ul>
<li>
<p>Imports should be sorted by <code>isort</code> as described above.</p>
</li>
<li>
<p>Prefer to import classes and functions rather than packages or
modules.</p>
<p>Example:</p>
<pre><code class="language-python">from synapse.types import UserID
...
user_id = UserID(local, server)
</code></pre>
<p>is preferred over:</p>
<pre><code class="language-python">from synapse import types
...
user_id = types.UserID(local, server)
</code></pre>
<p>(or any other variant).</p>
<p>This goes against the advice in the Google style guide, but it
means that errors in the name are caught early (at import time).</p>
</li>
<li>
<p>Avoid wildcard imports (<code>from synapse.types import *</code>) and
relative imports (<code>from .types import UserID</code>).</p>
</li>
</ul>
</li>
</ul>
<h2 id="configuration-code-and-documentation-format"><a class="header" href="#configuration-code-and-documentation-format">Configuration code and documentation format</a></h2>
<p>When adding a configuration option to the code, if several settings are grouped into a single dict, ensure that your code
correctly handles the top-level option being set to <code>None</code> (as it will be if no sub-options are enabled).</p>
<p>The <a href="usage/configuration/config_documentation.html">configuration manual</a> acts as a
reference to Synapse's configuration options for server administrators.
Remember that many readers will be unfamiliar with YAML and server
administration in general, so it is important that when you add
a configuration option the documentation be as easy to understand as possible, which
includes following a consistent format.</p>
<p>Some guidelines follow:</p>
<ul>
<li>
<p>Each option should be listed in the config manual with the following format:</p>
<ul>
<li>
<p>The name of the option, prefixed by <code>###</code>. </p>
</li>
<li>
<p>A comment which describes the default behaviour (i.e. what
happens if the setting is omitted), as well as what the effect
will be if the setting is changed.</p>
</li>
<li>
<p>An example setting, using backticks to define the code block</p>
<p>For boolean (on/off) options, convention is that this example
should be the <em>opposite</em> to the default. For other options, the example should give
some non-default value which is likely to be useful to the reader.</p>
</li>
</ul>
</li>
<li>
<p>There should be a horizontal rule between each option, which can be achieved by adding <code>---</code> before and
after the option.</p>
</li>
<li>
<p><code>true</code> and <code>false</code> are spelt thus (as opposed to <code>True</code>, etc.)</p>
</li>
</ul>
<p>Example:</p>
<hr />
<h3 id="modules"><a class="header" href="#modules"><code>modules</code></a></h3>
<p>Use the <code>module</code> sub-option to add a module under <code>modules</code> to extend functionality.
The <code>module</code> setting then has a sub-option, <code>config</code>, which can be used to define some configuration
for the <code>module</code>.</p>
<p>Defaults to none.</p>
<p>Example configuration:</p>
<pre><code class="language-yaml">modules:
- module: my_super_module.MySuperClass
config:
do_thing: true
- module: my_other_super_module.SomeClass
config: {}
</code></pre>
<hr />
<p>Note that the sample configuration is generated from the synapse code
and is maintained by a script, <code>scripts-dev/generate_sample_config.sh</code>.
Making sure that the output from this script matches the desired format
is left as an exercise for the reader!</p>
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