Drake code reviews use https://reviewable.io. This page documents some best practices for communicating effectively in Reviewable.
Avoid using the GitHub UI to comment on code during a review. Reviewable will import comments from GitHub, but cannot reliably match them to lines of diff.
When you enter comments in Reviewable, they are saved as drafts. Use the “publish” button to send them out in a batch. Reviewable will post the comments to the GitHub PR in a single, well-formatted block, generating email to everyone else following the PR.
Every time you push to your GitHub branch under review, Reviewable will snapshot a new diff. Because it maintains an independent diff series, you can rebase freely without corrupting the review history.
Life of a Reviewable Comment
All threads in Reviewable must be resolved before you can merge your PR.
The semantics of discussion resolution is more nuanced than GitHub’s default code review tool. We recommend to read this explanation to understand the details.
Before commenting on a line of code, reviewers should check to see if there is already a resolved discussion addressing the same topic. Resolved discussions are indicated by a small white check-mark in a grey circle to the left of the line of code.
Reviewers should click the eye-shaped buttons to indicate that they have reviewed a file. Reviewable will remember the revisions at which the file was reviewed, and mark them with an eye icon in the file history.
Each commit on Drake master should pass all unit tests and lint checks, should be logically cohesive (should not require other commits to make sense), and should have a meaningful commit message.
Therefore, our reviewable settings by default prevent a PR with more than one commit from being merged.
Often a PR may end up with more than one commit, including “work-in-progress” checkpoints or “fix review comments” pushes. In that case, when the PR is ready to merge, the author of a PR has three choices for how to proceed:
- Wait for the assigned Platform Reviewer to “Squash and merge” the PR. If time is of the essence, post a reminder to the PR.
- Locally (rebase and) squash the PR down to a single commit, and force-push that commit into the PR.
- Apply the label
status: squashing nowand then immediately use the “squash and merge” button to merge the PR, being careful to tweak the commit message in the web page’s edit box to be a sensible description of the change.
On the other hand, some PR authors carefully curate their commits so that each
individual commit on a PR meets the acceptance criteria on its own. In that
case, the author should apply the label
status: commits are properly
curated, which removes the single-commit requirement. PRs with this label
should be merged to master using the “Create a merge commit” option, not
“Squash and merge” option.
By default, your commit message’s subject line and full text will be collated into the release notes as part of the next numbered release. The collation involves human review (it is not completely mechanical) so while we are able to improve the text later as part of document assembly, please be kind to the human editor and do your best to provide a correct and helpful commit message up front.
Commits that do not meaningfully affect the release will be manually culled from
the release notes during editing. To aid the human editor in making that
determination, you may add the tag
release notes: none to the PR and the
commit will be omitted. For example, you should apply that tag to any PRs that
only fix code style problems, or only affect tests or documentation.
Commits that contain breaking changes receive special attention in the release
notes. To aid the human editor in making that determination, you must add the
release notes: breaking change to any PR that makes a breaking change
without a deprecation period.
Commits that change deprecations receive special attention in the release notes.
To aid the human editor in making that determination, you must add the tag
release notes: newly deprecated to any PR that adds new deprecations, or
release notes: removal of deprecated to any PR that removes deprecated
code whose date has passed. Removing deprecated code is not considered to be a
breaking change, so do not add
release notes: breaking change.
Joint Feature and Platform review
For a review to be considered complete, both Feature Review and Platform Review must be completed (see Review Process).
Therefore, our reviewable settings require at least two assigned reviewers. In
cases where the platform reviewer decides to double-count as feature review,
the reviewer should apply the label
status: single reviewer ok to note this
condition, which removes the two-assignee requirement.