Reviewable pull requests

This page offers some tips for making your pull requests easy to review. Following this advice will help the whole Zulip project move more quickly by saving maintainers time when they review your code. It will also make a big difference for getting your work integrated without delay. For a detailed overview of Zulip’s PR review process, see the pull request review process guide.

Posting a pull request

Before requesting a review for your pull request, follow our guide to carefully review and test your own code. Doing so can save many review round-trips.
Make sure the pull request template is filled out correctly, and that all the relevant points on the self-review checklist (if the repository has one) have been addressed.
Be sure to explicitly call out any open questions, concerns, or decisions you are uncertain about.

Addressing feedback

When you update your pull request after addressing a round of review feedback, be clear about which issues you’ve resolved (and how!).
Even more importantly, save time for your reviewers by indicating any feedback you haven’t addressed yet.

Working on larger projects

For a larger project, aim to create a series of small (less than 100 lines of code) commits that are each safely mergeable and move you towards your goal. A mergeable commit:

Is well-tested and passes all the tests. That is, changes to tests should be in the same commit as changes to the code that they are testing.
Does not make Zulip worse. For example, it is fine to add backend capabilities without adding a frontend to access them. It’s not fine to add a frontend component with no backend to make it work.

Ideally, when reviewing a branch you are working on, the maintainer should be able to verify and merge the first few commits and leave comments on the rest. It is by far the most efficient way to do collaborative development, since one is constantly making progress, we keep branches small, and developers don’t end up repeatedly reviewing the earlier parts of a pull request.

Here is some advice on how to proceed:

Use git rebase -i as much as you need to shape your commit structure. See the Git guide for useful resources on mastering Git.
If you need to refactor code, add tests, rename variables, or make other changes that do not change the functionality of the product, make those changes into a series of preparatory commits that can be merged independently of building the feature itself.
To figure out what refactoring needs to happen, you might first make a hacky attempt at hooking together the feature, with reading and print statements as part of the effort, to identify any refactoring needed or tests you want to write to help make sure your changes won’t break anything important as you work. Work out a fast and consistent test procedure for how to make sure the feature is working as planned.
Build a mergeable version of the feature on top of those refactorings. Whenever possible, find chunks of complexity that you can separate from the rest of the project.

See our commit discipline guide for more details on writing reviewable commits.

Tips and best practices

When writing comments for pull requests, it’s good to be familiar with GitHub’s basic formatting syntax. Here are some additional tips and best practices that Zulip contributors and maintainers have found helpful for writing clear and thorough pull request comments:

If there has been a conversation in the Zulip development community about the changes you’ve made or the issue your pull request addresses, please cross-link between your pull request and those conversations. This provides helpful context for maintainers and reviewers. Specifically, it’s best to link from your pull request to a specific message, as these links will still work even if the topic of the conversation is renamed, moved or resolved.

Once you’ve created a pull request on GitHub, you can use one of the custom linkifiers in the development community to easily link to your pull request from the relevant conversation.
For screenshots or screencasts of changes, putting them in details/summary tags reduces visual clutter and scroll length of pull request comments. This is especially useful when you have several screenshots and/or screencasts to include in your comment as you can put each image, or group of images, in separate details/summary tags.
```
<details>
<summary>Descriptive summary of image</summary>

![uploaded-image](uploaded-file-information)
</details>
```
For before and after images or videos of changes, using GithHub’s table syntax renders them side-by-side for quick and clear comparison. While this works well for narrow or small images, it can be hard to see details in large, full screen images and videos in this format.

Note that you can put the table syntax inside the details/summary tags described above as well.
```
### Descriptive header for images:
| Before | After |
| --- | --- |
| ![image-before](uploaded-file-information) | ![image-after](uploaded-file-information)
```
If you’ve updated existing documentation in your pull request, include a link to the current documentation above the screenshot of the updates. That way a reviewer can quickly access the current documentation while reviewing your changes.
```
[Current documentation](link-to-current-documentation-page)
![image-after](uploaded-file-information)
```
For updates or changes to CSS class rules, it’s a good practice to include the results of a git-grep search for the class name(s) to confirm that you’ve tested all the impacted areas of the UI and/or documentation.
```
$ git grep '.example-class-name' web/templates/ templates/
templates/corporate/...
templates/zerver/...
web/templates/...
```