bug#36903: 27.0.50; gnus registry vs. debbugs

[Eric Abrahamsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>
>>> I can't really imagine it being performance-related...  computing the
>>> specs take extremely little time.
>>>
>>> But it's possible, I guess.
>>
>> I'll patch locally and run it for a while.
>
> So I think we arrived at the conclusion that removing that removal
> should be safe (i.e., a noop) -- did you apply the patch?

I didn't, because it doesn't solve anything, and it seemed like a proper
fix would probably include this.

> I'm not sure how this related to the other registry stuff... What was
> the conclusion there?

The conclusion is I don't know what to do. Users who have customized
`gnus-summary-line-format' to draw info from the registry will see an
error if they start Gnus, stop Gnus, then start debbugs-gnu. That's
because stopping Gnus clears the registry, but starting debbugs-gnu
doesn't re-load it (because it doesn't load the users gnus.el file), and
the summary line format continues trying to access the registry object.

I naively tried *adding* `gnus-format-specs' to the list of variables to
clear, but of course that doesn't work because
`gnus-summary-line-format' remains customized, and `gnus-format-specs'
is simply re-built from that customized value when `debbugs-gnu' is
started.

This didn't use to be a problem because stopping Gnus used to leave the
registry hanging around. I changed that in 2815174f as part of
preventing the registry from being loaded twice at startup, and I just
think it's good practice not to leave this (potentially huge) data
structure lingering after shutdown.

I can imagine a few possible solutions, but none of them are very
appealing. debbugs-gnu seems stuck somewhere between "too Gnus" and "not
Gnus enough".

Eric