code-review

Code Review

A guide for reviewing code and having your code reviewed.

Everyone

• Accept that many programming decisions are opinions. Discuss tradeoffs, which you prefer, and reach a resolution quickly.
• Ask questions; don't make demands. ("What do you think about naming this :user_id?")
• Ask for clarification. ("I didn't understand. Can you clarify?")
• Avoid selective ownership of code. ("mine", "not mine", "yours")
• Avoid using terms that could be seen as referring to personal traits. ("dumb", "stupid") Assume everyone is attractive, intelligent, and well-meaning.
• Be explicit. Remember people don't always understand your intentions online.
• Be humble. ("I'm not sure - let's look it up.")
• Don't use hyperbole. ("always", "never", "endlessly", "nothing")
• Don't use sarcasm.
• Keep it real. If emoji, animated gifs, or humor aren't you, don't force them. If they are, use them with aplomb.
• Talk in person if there are too many "I didn't understand" or "Alternative solution:" comments. Post a follow-up comment summarizing offline discussion.

Having your code reviewed

• Be grateful for the reviewer's suggestions. ("Good call. I'll make that change.")
• Don't take it personally. The review is of the code, not you.
• Explain why the code exists. ("It's like that because of these reasons. Would it be more clear if I rename this class/file/method/variable?")
• Extract some changes and refactorings into future tickets/stories.
• Link to the code review from the ticket/story. ("Ready for review: http://github.com/organization/project/pull/1")
• Push commits based on earlier rounds of feedback as isolated commits to the branch. Do not squash until the branch is ready to merge. Reviewers should be able to read individual updates based on their earlier feedback.
• Seek to understand the reviewer's perspective.
• Try to respond to every comment.
• Wait to merge the branch until another person signs off.
• Wait to merge the branch until Continuous Integration (TDDium, TravisCI, etc.) tells you the test suite is green in the branch.

Reviewing code

Understand why the code is necessary (bug, user experience, refactoring). Then:

• Communicate which ideas you feel strongly about and those you don't.
• Identify ways to simplify the code while still solving the problem.
• If discussions turn too philosophical or academic, move the discussion offline to a regular Friday afternoon technique discussion. In the meantime, let the author make the final decision on alternative implementations.
• Offer alternative implementations, but assume the author already considered them. ("What do you think about using a custom validator here?")
• Seek to understand the author's perspective.
• Sign off on the pull request with a 👍 or "Ready to merge" comment.

Style comments

Reviewers should comment on missed style guidelines. Example comment:

[Style](../style):

> Order resourceful routes alphabetically by name.

An example response to style comments:

Whoops. Good catch, thanks. Fixed in a4994ec.

If you disagree with a guideline, open an issue on the guides repo rather than debating it within the code review. In the meantime, apply the guideline.

Ruby on Rails review

• Review data integrity closely, such as migrations that make irreversible changes to the data, and whether there is a related todo to make a database backup during the staging and production deploys.
• Review SQL queries for potential SQL injection.
• Review whether dependency upgrades include a reason in the commit message, such as a link to the dependency's ChangeLog or NEWS file.
• Review whether new database indexes are necessary if new columns or SQL queries were added.
• Review whether new scheduler (cron) tasks have been added and whether there is a related todo in the project management system to add it during the staging and production deploys.