Rustext's DirstateItem has no attribute 'v2_data', fsmonitor tries to access it.

[Raphaël Gomès]

On 10/23/23 01:16, Sietse Brouwer wrote:
> Hello everyone,
>
> I am writing about an AttributeError caused by fsmonitor trying to 
> access someDirstateItem.v2_data(), which is not exposed by 
> `mercurial.rustext.dirstate.DirstateItem` (but is exposed by 
> `mercurial.pure.parsers.DirstateItem`). Steps to reproduce and some 
> investigation below this e-mail.
Thanks for reporting this, fsmonitor is untested and not something we 
recommend mixing with Rust (because Rust is tested should give you the 
performance you're looking for without the flakiness). Can I ask why 
you're using fsmonitor?
>
> I'll file a bug and try my hand at a fix, but first I have a question: 
> does anybody know which module it is that needs fixing?
> - is hgext/fsmonitor/__init__.py wrong to try to access 
> DirStateItem.v2_data()?
> - Or is rust/hg-cpython/src/dirstate/item.rs:DirstateItem wrong in 
> that it lacks a method `v2_data`, when its Python counterpart has it?
>
I wrote this "fix" when we reworked the dirstate API because people at 
Mozilla use fsmonitor but without the Rust extensions, and we'd broken 
their workflow. I didn't realize we didn't expose the same interface 
from the Rust entry, but I'm not surprised, since it shouldn't be 
exposed past the serialization or FFI layers.

IMO what needs fixing is fsmonitor. It should use the public API until 
we figure out that accessing `not e.has_time or e.has_ambiguous_time` is 
slower than the bitmask hack I used last time.

Do you want to send the fix, or should I do it?

I hope this helps,
Raphaël

> Kind regards,
> Sietse
> Sietse Brouwer
>
> Steps to reproduce:
>
>     hg clone https://www.mercurial-scm.org/repo/hg-stable
>     cd hg-stable
>     hg up 6.5.2   # latest; but bug exists at least from 6.4.4
>     make PURE=--rust local
>     HGRCPATH= ./hg --config 'extensions.fsmonitor=' diff "set:tracked()"
>
>     # The above gives a long traceback that ends in
>       File 
> "/home/sbrouwer/lib/mercurial-main/hgext/fsmonitor/__init__.py", line 
> 354, in <setcomp>
>         or bool((e.v2_data()[0] & mask) ^ has_mtime)
>     AttributeError: 'mercurial.rustext.dirstate.DirstateItem' object 
> has no attribute 'v2_data'
>
> Further investigation:
>
> - error goes away when building with `make PURE=--pure local`
> - error goes away when the extension fsmonitor is disabled
> - error is not affected by turning repo dirstate storage format v2 
> on/off (via `hg debugupgrade --config format.use-dirstate-v2=1 --run` 
> to turn on, or =0 to turn off.)
>
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