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The Code Review Process
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#######################
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All code changes coming in to Bazaar are reviewed by someone else.
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Normally changes by core contributors are reviewed by one other core
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developer, and changes from other people are reviewed by two core
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developers. Use intelligent discretion if the patch is trivial.
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Good reviews do take time. They also regularly require a solid
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understanding of the overall code base. In practice, this means a small
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number of people often have a large review burden - with knowledge comes
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responsibility. No one likes their merge requests sitting in a queue going
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nowhere, so reviewing sooner rather than later is strongly encouraged.
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Please put a "cover letter" on your merge request explaining:
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* the reason **why** you're making this change
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* **how** this change achieves this purpose
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* anything else you may have fixed in passing
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* anything significant that you thought of doing, such as a more
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extensive fix or a different approach, but didn't or couldn't do now
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A good cover letter makes reviewers' lives easier because they can decide
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from the letter whether they agree with the purpose and approach, and then
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assess whether the patch actually does what the cover letter says.
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Explaining any "drive-by fixes" or roads not taken may also avoid queries
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from the reviewer. All in all this should give faster and better reviews.
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Sometimes writing the cover letter helps the submitter realize something
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else they need to do. The size of the cover letter should be proportional
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to the size and complexity of the patch.
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Reviewing proposed changes
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==========================
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Anyone is welcome to review code, and reply to the thread with their
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The simplest way to review a proposed change is to just read the patch on
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the list or in Bundle Buggy. For more complex changes it may be useful
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to make a new working tree or branch from trunk, and merge the proposed
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change into it, so you can experiment with the code or look at a wider
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There are three main requirements for code to get in:
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* Doesn't reduce test coverage: if it adds new methods or commands,
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there should be tests for them. There is a good test framework
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and plenty of examples to crib from, but if you are having trouble
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working out how to test something feel free to post a draft patch
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* Doesn't reduce design clarity, such as by entangling objects
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we're trying to separate. This is mostly something the more
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experienced reviewers need to help check.
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* Improves bugs, features, speed, or code simplicity.
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Code that goes in should not degrade any of these aspects. Patches are
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welcome that only cleanup the code without changing the external
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behaviour. The core developers take care to keep the code quality high
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and understandable while recognising that perfect is sometimes the enemy
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It is easy for reviews to make people notice other things which should be
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fixed but those things should not hold up the original fix being accepted.
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New things can easily be recorded in the Bug Tracker instead.
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It's normally much easier to review several smaller patches than one large
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one. You might want to use ``bzr-loom`` to maintain threads of related
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work, or submit a preparatory patch that will make your "real" change
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Checklist for reviewers
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=======================
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* Do you understand what the code's doing and why?
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* Will it perform reasonably for large inputs, both in memory size and
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run time? Are there some scenarios where performance should be
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* Is it tested, and are the tests at the right level? Are there both
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blackbox (command-line level) and API-oriented tests?
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* If this change will be visible to end users or API users, is it
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appropriately documented in NEWS?
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* Does it meet the coding standards below?
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* If it changes the user-visible behaviour, does it update the help
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strings and user documentation?
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* If it adds a new major concept or standard practice, does it update the
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developer documentation?
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* (your ideas here...)
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From May 2009 on, we prefer people to propose code reviews through
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* <https://launchpad.net/+tour/code-review>
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* <https://help.launchpad.net/Code/Review>
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Anyone can propose or comment on a merge proposal just by creating a
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There are two ways to create a new merge proposal: through the web
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interface or by email.
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Proposing a merge through the web
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---------------------------------
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To create the proposal through the web, first push your branch to Launchpad.
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For example, a branch dealing with documentation belonging to the Launchpad
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User mbp could be pushed as ::
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bzr push lp:~mbp/bzr/doc
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Then go to the branch's web page, which in this case would be
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<https://code.launchpad.net/~mbp/bzr/doc>. You can simplify this step by just
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You can then click "Propose for merging into another branch", and enter your
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cover letter (see above) into the web form. Typically you'll want to merge
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into ``~bzr/bzr/trunk`` which will be the default; you might also want to
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nominate merging into a release branch for a bug fix. There is the option to
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specify a specific reviewer or type of review, and you shouldn't normally
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Submitting the form takes you to the new page about the merge proposal
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containing the diff of the changes, comments by interested people, and
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controls to comment or vote on the change.
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Proposing a merge by mail
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-------------------------
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To propose a merge by mail, send a bundle to ``merge@code.launchpad.net``.
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You can generate a merge request like this::
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bzr send -o bug-1234.diff
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``bzr send`` can also send mail directly if you prefer; see the help.
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From <https://code.launchpad.net/bzr/+activereviews> you can see all
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currently active reviews, and choose one to comment on. This page also
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shows proposals that are now approved and should be merged by someone with
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removed
doc/developers/code-review.txt
