This page contains most of the information required for a developer to work with the Mattermost web app. Note that everything in this document will refer to working in the webapp directory of the main Mattermost repository unless otherwise stated.
If you haven’t done so already, set up your developer environment.
On your fork, create a feature branch for your changes. Name it MM-$NUMBER_$DESCRIPTION where $NUMBER is the Jira ticket number you are working on and $DESCRIPTION is a short description of your changes. Example branch names are MM-18150_plugin-panic-log and MM-22037_uppercase-email. You can also use the name GH-$NUMBER_$DESCRIPTION for tickets come from GitHub Issues.
Make the code changes required to complete your ticket, making sure to write or modify unit tests where appropriate. Use make test to run the unit tests.
To run your changes locally, you’ll need to run both the client and server. The server and client can either be run together or separately as follows:
You can run both together by using make run from the server directory. Both server and web app will be run together and can be stopped by using make stop. If you run into problems getting the server running this way, you may want to consider running them separately in case the output from one is hiding errors from the other.
You can run the server independently by running make run-server from its directory and, using another terminal, you can run the web app by running make run from the web app directory. Each can be stopped by running make stop-server or make stop from their respective directories.
Once you’ve done either of those, your server will be available at http://localhost:8065 by default. Changes to the web app will be built automatically, but changes to the server will only be applied if you restart the server by running make restart-server from the server directory.
If you added or changed any translatable text, you will need to update the English translation files to make them available to translators for other languages. You can do that by navigating to channels and running make i18n-extract to update src/i18n/en.json.
en.json should be modified directly from this repository. Other languages’ translation files are updated using Weblate.Before submitting a PR, make sure to check your coding style and run the automated tests on your changes. These are checked automatically by CI, but they should be run manually before submitting changes to ensure the review process goes smoothly.
make check-style. If any problems are encountered, they may be able to be automatically fixed by using make fix-style.make check-types.make test.Commit your changes, push your branch and create a pull request.
Respond to feedback on your pull request and make changes as necessary by committing to your branch and pushing it. Your branch should be kept roughly up to date by merging master into it periodically. This can either be done using `git merge` or, as long as there are no conflicts, by commenting /update-branch on the PR.
That’s it! Rejoice that you’ve helped make Mattermost better.
During development you may want to reset the database and generate random data for testing your changes. See the corresponding section of the server developer workflow for how to do that.