[LLVMdev] Phabricator (Was: Automatically adding llvm-commits as CC)

[Hal Finkel]

----- Original Message -----
> From: "Justin Bogner" <mail at justinbogner.com>
> To: "llvmdev" <llvmdev at cs.uiuc.edu>
> Cc: "Matthias Braun" <matze at braunis.de>
> Sent: Wednesday, May 27, 2015 1:54:39 AM
> Subject: [LLVMdev] Phabricator (Was: Automatically adding llvm-commits as CC)
> 
> Moving this to llvmdev - it needs a bit of a wider audience.
> 
> There are several issues with phabricator, and in the current state
> of
> things there's a huge amount of confusion on how to even report
> problems, let alone try to resolve them.
> 
> Recently I started a thread about empty emails, was directed to the
> phabricator project's bug tracker, and told there that LLVM has
> customized phabricator so there's nothing they (phab) can do. Soon
> after, the message I'm replying to below was sent to llvm-admin, and
> it
> was pointed out that they don't maintain phab, so there's nothing
> *they*
> can do:
> 
> Chandler Carruth <chandlerc at google.com> writes:
> > On Tue, May 26, 2015 at 1:31 PM Tanya Lattner <tonic at nondot.org>
> > wrote:
> >> On Apr 30, 2015, at 4:25 PM, Matthias Braun <matze at braunis.de>
> >> wrote:
> >>> This happens to me as well from time to time. I wonder if there
> >>> is a
> >>> way to have phabricator add llvm-commits to CC as soon as
> >>> "repository llvm" or "project llvm" is selected. Or maybe
> >>> revisions
> >>> with an empty subscribers field could be rejected.
> >>
> >> llvm-admin doesn't administrate the phabricator. You need to
> >> contact:
> >> Manuel Klimek or Chandler Carruth.
> >
> > This has been discussed before. If you look at the prior
> > discussions on
> > llvmdev about phabricator you should find lots of references to it.
> >
> > I don't want to repeat the entire discussion but the essence is
> > "sure, it
> > could be done, but someone must write the code to do it". The code
> > is posted
> > where you can get at it, we can even put it in an LLVM repository
> > if that
> > helps, but so far none have stepped up to write the code to make
> > this happen.
> > I donated hardware to get this whole thing started for a year, and
> > Manuel did
> > the much more time consuming work to get it up to the point it is
> > currently
> > at, but I don't think he has a lot more time to devote to it.
> 
> I appreciate the effort that you (Chandler) and Manuel have put into
> this, but I find this answer a bit lacking in important details.
> 
> Where is the code posted? Where is the documentation about that? The
> docs at http://llvm.org/docs/Phabricator.html don't tell me anything
> more than "Please let us know whether you like it and what could be
> improved!".
> 
> Most importantly, where can I file bugs about LLVM's phabricator
> instance?
> 
> > Fundamentally, we need folks in the community to contribute if they
> > have
> > significant problems with the tools.
> 
> Personally, as a reviewer, I find phabricator reviews strictly worse
> than sending a patch to the llvm-commits list. Off the top of my
> head,
> with phab:
> 
> - The patch doesn't always show up on the mailing list,
> - Replies to review comments and the patch that accompanies them come
> in
>   different emails,
> - Several emails show up in your inbox with nothing but a link, and
> no
>   indication why they were sent,
> - Comments and responses to comments sometimes show up twice - once
> from
>   the person who says them and another time from phab,

I find all of these to be only a minor inconvenience.

> - Patches are often (but not always) duplicated - both inline *and*
>   attached. This is bizarre, useless, and confuses tools like git-am.

I disagree; this is a convenient feature for small patches.

> 
> With an email it's trivial to read the diff or to apply the patch to
> an
> LLVM checkout to look at in more detail, including building it or
> looking at the result in a text editor.

There are three things that the web interface gives me that I find invaluable:

 1. The ability to see, selectively, the full context (or at least additional context) of the patch

 2. The ability to filter out white-space only changes, and identify moved regions of code, and highlight sub-line changes

 3. The ability to quickly compare changes between different versions of a patch

In addition, the ability to insert formatted comments near particular lines of code is really quite nice.

> 
> I realize that quite a few people find the web interface helpful, so
> I've refrained from asking people to post patches directly rather
> than
> using phab so far, but that *would* solve my problems with the tool.
> We
> at least need some clear information on how to file bugs and where to
> look if we want to try to fix the problems ourselves.

I agree; we certainly need to clarify this.

 -Hal

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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory