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<p>The code of Synapse is written in Python 3. To do pretty much anything, you'll need <ahref="https://www.python.org/downloads/">a recent version of Python 3</a>. Your Python also needs support for <ahref="https://docs.python.org/3/library/venv.html">virtual environments</a>. This is usually built-in, but some Linux distributions like Debian and Ubuntu split it out into its own package. Running <code>sudo apt install python3-venv</code> should be enough.</p>
<p>Synapse can connect to PostgreSQL via the <ahref="https://pypi.org/project/psycopg2/">psycopg2</a> Python library. Building this library from source requires access to PostgreSQL's C header files. On Debian or Ubuntu Linux, these can be installed with <code>sudo apt install libpq-dev</code>.</p>
<p>The source code of Synapse is hosted on GitHub. You will also need <ahref="https://github.com/git-guides/install-git">a recent version of git</a>.</p>
<p>For some tests, you will need <ahref="https://docs.docker.com/get-docker/">a recent version of Docker</a>.</p>
<h1id="3-get-the-source"><aclass="header"href="#3-get-the-source">3. Get the source.</a></h1>
<p>The preferred and easiest way to contribute changes is to fork the relevant
project on GitHub, and then <ahref="https://help.github.com/articles/using-pull-requests/">create a pull request</a> to ask us to pull your
changes into our repo.</p>
<p>Please base your changes on the <code>develop</code> branch.</p>
<h1id="6-pick-an-issue"><aclass="header"href="#6-pick-an-issue">6. Pick an issue.</a></h1>
<p>Fix your favorite problem or perhaps find a <ahref="https://github.com/matrix-org/synapse/issues?q=is%3Aopen+is%3Aissue+label%3A%22Good+First+Issue%22">Good First Issue</a>
<h1id="7-turn-coffee-into-code-and-documentation"><aclass="header"href="#7-turn-coffee-into-code-and-documentation">7. Turn coffee into code and documentation!</a></h1>
<pre><code>docker: Error response from daemon: driver failed programming external connectivity on endpoint nice_ride (b57bbe2e251b70015518d00c9981e8cb8346b5c785250341a6c53e3c899875f1): Error starting userland proxy: listen tcp4 0.0.0.0:5432: bind: address already in use.
</code></pre>
<p>then something is already bound to port 5432. You're probably already running postgres locally.</p>
<p>Once you have a postgres server running, invoke <code>trial</code> in a second terminal:</p>
<pre><codeclass="language-shell">SYNAPSE_POSTGRES=1 SYNAPSE_POSTGRES_HOST=127.0.0.1 SYNAPSE_POSTGRES_USER=postgres SYNAPSE_POSTGRES_PASSWORD=mysecretpassword poetry run trial tests
</code></pre>
<h4id="using-an-existing-postgres-installation"><aclass="header"href="#using-an-existing-postgres-installation">Using an existing Postgres installation</a></h4>
<p>If you have postgres already installed on your system, you can run <code>trial</code> with the
<h2id="run-the-integration-tests-sytest"><aclass="header"href="#run-the-integration-tests-sytest">Run the integration tests (<ahref="https://github.com/matrix-org/sytest">Sytest</a>).</a></h2>
<p>(Note that the paths must be full paths! You could also write <code>$(realpath relative/path)</code> if needed.)</p>
<p>This configuration should generally cover your needs.</p>
<ul>
<li>To run with Postgres, supply the <code>-e POSTGRES=1 -e MULTI_POSTGRES=1</code> environment flags.</li>
<li>To run with Synapse in worker mode, supply the <code>-e WORKERS=1 -e REDIS=1</code> environment flags (in addition to the Postgres flags).</li>
</ul>
<p>For more details about other configurations, see the <ahref="https://github.com/matrix-org/sytest/blob/develop/docker/README.md">Docker-specific documentation in the SyTest repo</a>.</p>
<h2id="run-the-integration-tests-complement"><aclass="header"href="#run-the-integration-tests-complement">Run the integration tests (<ahref="https://github.com/matrix-org/complement">Complement</a>).</a></h2>
<p><ahref="https://github.com/matrix-org/complement">Complement</a> is a suite of black box tests that can be run on any homeserver implementation. It can also be thought of as end-to-end (e2e) tests.</p>
<p>It's often nice to develop on Synapse and write Complement tests at the same time.
Here is how to run your local Synapse checkout against your local Complement checkout.</p>
<p>(checkout <ahref="https://github.com/matrix-org/complement"><code>complement</code></a> alongside your <code>synapse</code> checkout)</p>
<p>To run a specific test file, you can pass the test name at the end of the command. The name passed comes from the naming structure in your Complement tests. If you're unsure of the name, you can do a full run and copy it from the test output:</p>
<h3id="prettier-formatting-with-gotestfmt"><aclass="header"href="#prettier-formatting-with-gotestfmt">Prettier formatting with <code>gotestfmt</code></a></h3>
<p>If you want to format the output of the tests the same way as it looks in CI,
<h3id="access-database-for-homeserver-after-complement-test-runs"><aclass="header"href="#access-database-for-homeserver-after-complement-test-runs">Access database for homeserver after Complement test runs.</a></h3>
<p>If you're curious what the database looks like after you run some tests, here are some steps to get you going in Synapse:</p>
<ol>
<li>In your Complement test comment out <code>defer deployment.Destroy(t)</code> and replace with <code>defer time.Sleep(2 * time.Hour)</code> to keep the homeserver running after the tests complete</li>
<li>Start the Complement tests</li>
<li>Find the name of the container, <code>docker ps -f name=complement_</code> (this will filter for just the Compelement related Docker containers)</li>
<li>Access the container replacing the name with what you found in the previous step: <code>docker exec -it complement_1_hs_with_application_service.hs1_2 /bin/bash</code></li>
<li>Then run <code>sqlite3</code> and open the database <code>.open /conf/homeserver.db</code> (this db path comes from the Synapse homeserver.yaml)</li>
<h1id="9-submit-your-patch"><aclass="header"href="#9-submit-your-patch">9. Submit your patch.</a></h1>
<p>Once you're happy with your patch, it's time to prepare a Pull Request.</p>
<p>To prepare a Pull Request, please:</p>
<ol>
<li>verify that <ahref="#test-test-test">all the tests pass</a>, including the coding style;</li>
<li><ahref="#sign-off">sign off</a> your contribution;</li>
<li><code>git push</code> your commit to your fork of Synapse;</li>
<li>on GitHub, <ahref="https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-a-pull-request">create the Pull Request</a>;</li>
<li>add a <ahref="#changelog">changelog entry</a> and push it to your Pull Request;</li>
<li>for most contributors, that's all - however, if you are a member of the organization <code>matrix-org</code>, on GitHub, please request a review from <code>matrix.org / Synapse Core</code>.</li>
<p>This file will become part of our <ahref="https://github.com/matrix-org/synapse/blob/master/CHANGES.md">changelog</a> at the next
release, so the content of the file should be a short description of your
change in the same style as the rest of the changelog. The file can contain Markdown
formatting, and should end with a full stop (.) or an exclamation mark (!) for
consistency.</p>
<p>Adding credits to the changelog is encouraged, we value your
contributions and would like to have you shouted out in the release notes!</p>
<p>For example, a fix in PR #1234 would have its changelog entry in
<code>changelog.d/1234.bugfix</code>, and contain content like:</p>
<blockquote>
<p>The security levels of Florbs are now validated when received
via the <code>/federation/florb</code> endpoint. Contributed by Jane Matrix.</p>
</blockquote>
<p>If there are multiple pull requests involved in a single bugfix/feature/etc,
then the content for each <code>changelog.d</code> file should be the same. Towncrier will
merge the matching files together into a single changelog entry when we come to
release.</p>
<h3id="how-do-i-know-what-to-call-the-changelog-file-before-i-create-the-pr"><aclass="header"href="#how-do-i-know-what-to-call-the-changelog-file-before-i-create-the-pr">How do I know what to call the changelog file before I create the PR?</a></h3>
<p>Obviously, you don't know if you should call your newsfile
<code>1234.bugfix</code> or <code>5678.bugfix</code> until you create the PR, which leads to a
chicken-and-egg problem.</p>
<p>There are two options for solving this:</p>
<ol>
<li>
<p>Open the PR without a changelog file, see what number you got, and <em>then</em>
add the changelog file to your branch (see <ahref="#updating-your-pull-request">Updating your pull
request</a>), or:</p>
</li>
<li>
<p>Look at the <ahref="https://github.com/matrix-org/synapse/issues?q=">list of all
issues/PRs</a>, add one to the
highest number you see, and quickly open the PR before somebody else claims
<h1id="10-turn-feedback-into-better-code"><aclass="header"href="#10-turn-feedback-into-better-code">10. Turn feedback into better code.</a></h1>
<p>Once the Pull Request is opened, you will see a few things:</p>
<ol>
<li>our automated CI (Continuous Integration) pipeline will run (again) the linters, the unit tests, the integration tests and more;</li>
<li>one or more of the developers will take a look at your Pull Request and offer feedback.</li>
</ol>
<p>From this point, you should:</p>
<ol>
<li>Look at the results of the CI pipeline.
<ul>
<li>If there is any error, fix the error.</li>
</ul>
</li>
<li>If a developer has requested changes, make these changes and let us know if it is ready for a developer to review again.</li>
<li>Create a new commit with the changes.
<ul>
<li>Please do NOT overwrite the history. New commits make the reviewer's life easier.</li>
<li>Push this commits to your Pull Request.</li>
</ul>
</li>
<li>Back to 1.</li>
</ol>
<p>Once both the CI and the developers are happy, the patch will be merged into Synapse and released shortly!</p>
<h1id="11-find-a-new-issue"><aclass="header"href="#11-find-a-new-issue">11. Find a new issue.</a></h1>
<p>By now, you know the drill!</p>
<h1id="notes-for-maintainers-on-merging-prs-etc"><aclass="header"href="#notes-for-maintainers-on-merging-prs-etc">Notes for maintainers on merging PRs etc</a></h1>
<p>There are some notes for those with commit access to the project on how we
