llvm dev - May 2021 - [RFC] Deprecate email code reviews in favor of Phabricator

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


-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20210503/62b4adbb/attachment.html>

On Mon, 3 May 2021, Krzysztof Parzyszek via cfe-dev wrote:
> 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
I don't mind formalizing that reviews are done on phabricator only. 
However following projects that way would, most probably, have one 
quite notable drawback compared with the current mailing list based 
approach:

Right now, it's easy to distinguish between mails requiring different 
levels of attention; ones with me in the To or CC fields are more visible 
and I try to read all of them. I have personal Herald rules that CC me on 
topics that I track. But I also browse the rest of the mails (quickly 
glancing usually only) for other topics I might be interested in.

My suspicion is that if the mail delivery is in the form of a personal 
subscription directly from Phabricator, it becomes much harder to 
distinguish mails that stem from just following a project as a whole, vs 
ones where I'm specifically CCd.

On the other hand I guess there can be other ways of filtering the mails 
do distinguish between those cases, so maybe it would be manageable?

// Martin

Hello,

I have started reading the tutorial about writing a LLVM backend, but I 
got stuck very quickly following it.
The tutorial says that it focuses on existing examples from 
llvm/lib/Target, in the LLVM release. As far as
I can see, the current release versions of LLVM do not contain these 
examples.

I did find the examples in the source distribution of LLVM, and 
currently I am building the source, however
my question is the following:

Is it possible to develop a LLVM backend using for example the LLVM 
distribution available by default
on Ubuntu (20.04), or possibly the binary distribution for Windows?

Best regards,

Viorel Preoteasa

On Mon, May 03, 2021 at 05:24:24PM +0000, Krzysztof Parzyszek via llvm-dev
wrote:
>    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:
Wouldn't this make it more difficult for sites that archive the lists?
Right now it all works. If the lists were eliminated then it would be
harder to archive. Not impossible, but it would be more work.

Plus, how long would it take for archive sites to switch over? How much
history would only exist in Phab's database?

Couldn't the commit lists be made read-only except from Phab? That would
force reviews to happen on Phab but otherwise keep all existing email
setups working.
-- 
"A method for inducing cats to exercise consists of directing a beam of
invisible light produced by a hand-held laser apparatus onto the floor ...
in the vicinity of the cat, then moving the laser ... in an irregular way
fascinating to cats,..." -- US patent 5443036, "Method of exercising a
cat"

In my view, this email is really too different topics.  Given that, my 
response is split into two parts.

First, should we make phabricator our default for code review?  I am not 
opposed to this.  I don't particular support it either, but I would not 
spend time arguing against it.  I would suggest that we re-frame the 
proposal to distinguish precommit and post commit review - with only the 
former moving to phabricator.  I have not seen post-commit done 
successfully on phabricator to date in any wide spread manner.

Second, should we consider retiring llvm-commits and the other mailing 
lists?  My gut response is a flat out NO!!!!  What we have works.  I am 
highly reluctant to run the risk of breaking our existing processes - 
which for all their problems mostly work - for the, to me, seemingly 
very minimal value obtained by moving away from email discussion.  Post 
commit review in email works.  I strongly suspect that if you try to 
change that, you will either simply drive out post commit review 
discussion (bad idea!) or discussions will move to private email 
exchanges (bad idea!).  I'm open to being convinced here, but the burden 
of proof is high. The risk we'd be talking about with such a transition 
is immense.

Philip

On 5/3/2021 10:24 AM, Krzysztof Parzyszek via llvm-dev
wrote:
>
> *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
>     <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 
>
<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 
> <https://lists.llvm.org/pipermail/llvm-dev/2021-April/150129.html>
>
> [3] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150136.html 
> <https://lists.llvm.org/pipermail/llvm-dev/2021-April/150136.html>
>
> [4] https://lists.llvm.org/pipermail/llvm-dev/2021-April/150139.html 
> <https://lists.llvm.org/pipermail/llvm-dev/2021-April/150139.html>
>
> [5] https://reviews.llvm.org/project/view/104/ 
> <https://reviews.llvm.org/project/view/104/>
>
> [6] https://reviews.llvm.org/D101432
<https://reviews.llvm.org/D101432>
>
> [7] https://reviews.llvm.org/H769 <https://reviews.llvm.org/H769>
>
> -- 
>
> Krzysztof Parzyszek kparzysz at quicinc.com 
> <mailto:kparzysz at quicinc.com>   AI tools development
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20210503/bd7cce67/attachment.html>

On Mon, May 3, 2021 at 1:24 PM Krzysztof Parzyszek via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
>
> 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).”
Personally, I am in favor of this policy for initiating code reviews,
but am opposed to it for post-commit feedback. The problem, as I see
it, is that not every change *gets* code review via Phab and the email
lists are the only place on which to provide that post-commit
feedback. This largely comes up in two ways: NFC changes and changes
made by code owners in the area of the compiler which they own. We
still need *some* mechanism by which to provide them post-commit
feedback. Currently, the way we provide that is frequently via an
email reply to the commit message on the *-commits list so that the
issue can be seen by both the patch author and the community at large.
> Current situation:
>
> 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.)
> 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.
> 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:
>
> 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.
> Review authors and reviewers would only need to monitor one source of
comments without the fear that a review comment may end up overlooked.
> Local Phabricator extensions would no longer be needed.
>
>
>
> Concerns:
>
> 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.
The Phab commit message does not have any subscribers though, and so
my understanding is that comments on that Phab interface are not
communicated out to the community as a whole, which means the
community may miss out on important post-commit-review information
like general awareness of the problem, workarounds people can use
until the author corrects something, alternative ideas on how to fix
the issue, etc. Or do I misunderstand the way Phab works in this
workflow?

Also, "the commenter would need to find the Phabricator commit"
concerns me -- adding extra burden on the people providing feedback
means that *some* amount of those people will struggle enough to
simply not provide that feedback. Responding to an email is about as
low as I think we can set that bar, so the current approach has better
ergonomics for giving feedback. When I look at an existing NFC commit
email
(https://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20210503/368413.html),
I don't see any direct link back to the Phabricator commit, so I have
to know to get the hash and try using that with an
https://reviews.llvm.org/rG in front of it. None of the existing links
in the email get me to where I'd need to go to add my review feedback,
but hitting the Reply button in my mail client will work. Adding a
third link and telling people "click on the link in the email" means
they've got a 50/50 shot of getting the right link because one of the
links goes to GitHub where you can also add comments.
> 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.
> 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].
Tangential complaint -- our use of Herald causes some pain for me as a
list moderator because we've reached the point where Herald
automatically adds so many subscribers to a review that it gets marked
as spam for every email that is generated for the review. It's to the
point on cfe-dev where over half of the moderated emails are
consistently not spam some weeks. This delays the community receiving
the information while the patch reviewers/subscribers continue to get
it. In turn, this causes a problem where sometimes the people
subscribed to the patch say something is OK and the patch lands before
the community ever sees the review and has a chance to comment on it.
I'm wary of suggestions that involve heavier use of Herald until we
get that mailing list issue resolved.
> 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.
Given how often Phabricator goes down (which is not super often, but
often enough that people know it happens), I am deeply uncomfortable
with the idea of shutting down the current *-commits mailing lists
because of the chance for data loss. Personally, I think the *-commits
lists are working well and I would prefer they be left alone.

~Aaron
>
> 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   AI tools development
>
>
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev