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<p>The code of Synapse is written in Python 3. To do pretty much anything, you'll need <ahref="https://wiki.python.org/moin/BeginnersGuide/Download">a recent version of Python 3</a>.</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>
<p>This will install the developer dependencies for the project.</p>
<h1id="5-get-in-touch"><aclass="header"href="#5-get-in-touch">5. Get in touch.</a></h1>
<p>Join our developer community on Matrix: <ahref="https://matrix.to/#/#synapse-dev:matrix.org">#synapse-dev:matrix.org</a>!</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>
to work on.</p>
<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>
<p>There is a growing amount of documentation located in 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>The integration tests are a more comprehensive suite of tests. They
run a full version of Synapse, including your changes, to check if
anything was broken. They are slower than the unit tests but will
typically catch more errors.</p>
<p>The following command will let you run the integration test with the most common
configuration:</p>
<pre><codeclass="language-sh">$ docker run --rm -it -v /path/where/you/have/cloned/the/repository\:/src:ro -v /path/to/where/you/want/logs\:/logs matrixdotorg/sytest-synapse:buster
</code></pre>
<p>This configuration should generally cover your needs. For more details about other configurations, see <ahref="https://github.com/matrix-org/sytest/blob/develop/docker/README.md">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="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>
</ol>
<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>
<li>if you need to update your PR, please avoid rebasing and just add new commits to your branch.</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
<ahref="https://github.com/docker/docker/blob/master/CONTRIBUTING.md">Docker</a>, and many other
projects use: the DCO (Developer Certificate of Origin:
http://developercertificate.org/). This is a simple declaration that you wrote
the contribution or otherwise have the right to contribute it to Matrix:</p>
<pre><code>Developer Certificate of Origin
Version 1.1
Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
660 York Street, Suite 102,
San Francisco, CA 94110 USA
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Developer's Certificate of Origin 1.1
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
</code></pre>
<p>If you agree to this for your contribution, then all that's needed is to
include the line in your commit or pull request comment:</p>
<pre><code>Signed-off-by: Your Name <your@email.example.org>
</code></pre>
<p>We accept contributions under a legally identifiable name, such as
your name on government documentation or common-law names (names
claimed by legitimate usage or repute). Unfortunately, we cannot
accept anonymous contributions at this time.</p>
<p>Git allows you to add this signoff automatically when using the <code>-s</code>
flag to <code>git commit</code>, which uses the name and email set in your
<code>user.name</code> and <code>user.email</code> git configs.</p>
<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
