element-web/docs/review.md

Review Guidelines

The following summarises review guidelines that we follow for pull requests in Element Web and other supporting repos. These are just guidelines (not strict rules) and may be updated over time.

Code Review

When reviewing code, here are some things we look for and also things we avoid:

We review for

• Correctness
• Performance
• Accessibility
• Security
• Quality via automated and manual testing
• Comments and documentation where needed
• Sharing knowledge of different areas among the team
• Ensuring it's something we're comfortable maintaining for the long term
• Progress indicators and local echo where appropriate with network activity

We should avoid

• Style nits that are already handled by the linter
• Dramatically increasing scope

Good practices

• Use empathetic language
  • See also Mindful Communication in Code Reviews and How to Do Code Reviews Like a Human
• Authors should prefer smaller commits for easier reviewing and bisection
• Reviewers should be explicit about required versus optional changes
  • Reviews are conversations and the PR author should feel comfortable discussing and pushing back on changes before making them
• Reviewers are encouraged to ask for tests where they believe it is reasonable
• Core team should lead by example through their tone and language
• Take the time to thank and point out good code changes
• Using softer language like "please" and "what do you think?" goes a long way towards making others feel like colleagues working towards a common goal

Workflow

• Authors should request review from the element-web team by default (if someone on the team is clearly the expert in an area, a direct review request to them may be more appropriate)
• Reviewers should remove the team review request and request review from themselves when starting a review to avoid double review
• If there are multiple related PRs authors should reference each of the PRs in the others before requesting review. Reviewers might start reviewing from different places and could miss other required PRs.
• Avoid force pushing to a PR after the first round of review
• Use the GitHub default of merge commits when landing (avoid alternate options like squash or rebase)
• PR author merges after review (assuming they have write access)
• Assign issues only when in progress to indicate to others what can be picked up

Code Quality

In the past, we have occasionally written different kinds of tests for Element and the SDKs, but it hasn't been a consistent focus. Going forward, we'd like to change that.

• For new features, code reviewers will expect some form of automated testing to be included by default
• For bug fixes, regression tests are of course great to have, but we don't want to block fixes on this, so we won't require them at this time

The above policy is not a strict rule, but instead it's meant to be a conversation between the author and reviewer. As an author, try to think about writing a test when making your next change. As a reviewer, try to think about how you might test the area of code you are reviewing. If the reviewer agrees it would be quite difficult to test some new feature, then it's okay for them to accept the change without tests for now, but we'd eventually like to be more strict about this further down the road.

If you do spot areas that are quite hard to test today, please let us know in #element-dev:matrix.org. We can work on improving the app architecture and testing helpers so that future tests are easier for everyone to write, but we won't know which parts are difficult unless people shout when stumbling through them.

We recognise that this testing policy will slow things down a bit, but overall it should encourage better long-term health of the app and give everyone more confidence when making changes as coverage increases over time.

For changes guarded by a feature flag, we currently lean towards prioritising our ability to evolve quickly using such flags and thus we will not currently require tests to appear at the same time as the initial landing of features guarded by flags, as long as (for new flagged features going forward) the feature author understands that they are effectively deferring part of their work (adding tests) until later and tests are expected to appear before the feature can be enabled by default.

Design and Product Review

We want to ensure that all changes to Element fit with our design and product vision. We often request review from those teams so they can provide their perspective.

In more detail, our usual process for changes that affect the UI or alter user functionality is:

• For changes that will go live when merged, always flag Design and Product teams as appropriate
• For changes guarded by a feature flag, Design and Product review is not required (though may still be useful) since we can continue tweaking

As it can be difficult to review design work from looking at just the changed files in a PR, a preview site that includes your changes will be added automatically so that anyone who's interested can try them out easily.

Before starting work on a feature, it's best to ensure your plan aligns well with our vision for Element. Please chat with the team in #element-dev:matrix.org before you start so we can ensure it's something we'd be willing to merge.