[cfe-dev] [RFC] Deprecate email code reviews in favor of Phabricator

[Krzysztof Parzyszek via cfe-dev]

Statement:

Our current code review policy states[1]:

"Code reviews are conducted, in order of preference, on our web-based code-review tool (see Code Reviews with Phabricator), by email on the relevant project's commit mailing list, on the project's development list, or on the bug tracker."

This proposal is to limit code reviews only to Phabricator.  This would apply to all projects in the LLVM monorepo.  With the change in effect, the amended policy would read:

"Code reviews are conducted on our web-based code-review tool (see Code Reviews with Phabricator)."



Current situation:

  1.  In a recent llvm-dev thread[2], Christian Kühnel pointed out that pre-commit code reviews rarely originate via an email (most are started on Phabricator), although, as others pointed out, email responses to an ongoing review are not uncommon.  (That thread also contains examples of mishaps related to the email-Phabricator interactions, or email handling itself.)
  2.  I don't have specific information about post-commit reviews.  It seems like the most common form is an email reply to the auto-generated commit message, although (in my personal experience), "raising a concern" in the commit on Phabricator or commenting in the pre-commit review is usually sufficient to get author's attention.
  3.  We have Phabricator patches that automatically apply email comments to the Phabricator reviews, although reportedly this functionality is not fully reliable[3,4].  This can cause review comments to be lost in the email traffic.



Benefits:

  1.  Single way of doing code reviews: code reviews are a key part of the development process, and having one way of performing them would make the process clearer and unambiguous.
  2.  Review authors and reviewers would only need to monitor one source of comments without the fear that a review comment may end up overlooked.
  3.  Local Phabricator extensions would no longer be needed.



Concerns:

  1.  For post-commit reviews, the commenter would need to find either the original review, or the Phabricator commit (e.g. https://reviews.llvm.org/rG06234f758e19).  Those are communicated (perhaps ironically) via email, which implies that those automatic emails should remain in place.
  2.  The current policy has been in place for a long time and it's expected that some people will continue using email for reviews out of habit or due to lack of awareness of the policy change.
  3.  Because of the larger variety, email clients may offer better accessibility options than web browsers.



Potential future direction:
This section presents a potential future evolution of the review process.  Christian has conducted experiments suggesting that we can replace the XXX-commits mailing lists with notifications directly from Phabricator:

  *   For each of the mailing lists, we create a "project" with the same name in Phabricator, e.g. [5]. Every Phabricator user can join/leave these projects on their own.
  *   Everyone on these projects will receive the same email notifications from Phabricator as we have on the mailing lists. This is configured via "Herald" rules in Phabricator, as today, e.g. [7].
  *   Users can reply to these email notifications and Phabricator will incorporate these responses with their email client, see [6] for some example emails. Quoting and markup is supported as well.
  *   We do NOT migrate the membership lists. Users need to sign up to the projects manually. We will send an email with instructions to the mailing lists once everything is set up.
  *   The current XXX-commits mailing lists will be shut down
  *   The timeline for the migration is to be defined.
For experimenting, feel free to sign up to the prototype project at [5] . This project receives all commit and code review notifications.




[1] https://llvm.org/docs/CodeReview.html#what-tools-are-used-for-code-review

[2] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150129.html

[3] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150136.html

[4] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150139.html
[5] https://reviews.llvm.org/project/view/104/
[6] https://reviews.llvm.org/D101432
[7] https://reviews.llvm.org/H769





--

Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at quicinc.com>   AI tools development


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