bug#62694: 30.0.50; eglot-tests fails with recent pylsp

[Michael Albinus <michael.albinus@gmx.de>]

João Távora <joaotavora@gmail.com> writes:

Hi João,

>>>> That earlier proposals were not complete, optimal, or up to yours or
>>>> anyone's standards does not warrant degrading them, IMO.  
>>>
>>> - vague: there are no details, just the idea of "checking if the server
>>>   is up to the job".
>>
>> I've shown you the Eglot traces for one test case on both Debian pylsp
>> (failed) and Fedora pylsp (succeeded). I still have no idea whether the
>> Debian flavour is inside the LSP specs or not. But if it returns
>> out-of-spec replies, I guess eglot should raise an Emacs error
>> indicating this fact.
>
> It's _not_ an out-of-spec reply.  It's just a insuficient in-spec reply
> from a poorly installed or configured server.

If it is an on-spec reply, eglot shall handle this. If there isn't
sufficient information in the reply, eglot shall err out with this
information.

> The point of these tests, as I've explained multiple times, is not to
> test the servers, rather eglot.el's particularly its interactions with
> other emacs facilities, such as xref, completion, flymake etc.  Any
> server will do, as long as it is reasonably well-behaved and
> predictable.  That's why I switched to clangd and all this discussion
> is moot now.

It isn't only the tests. You cannot prevent that a curious user, with
the brand new Emacs 29 installed, reads the NEWS and knows there's
eglot. She installs the Debian pylsp server (because that's what Debian
offers), tries it, and fails. And you'll ghet a bug report.

>> Based on this fact, you could always catch this specific error in the
>> tests, and say that the server is not suited. Whether you shall skip
>> or err out the test then is something else; until now it isn't obvious
>> that a failed eglot test is due to the (possible) server misbehavior,
>> or due to an eglot error. At least this information should be shown.
>
> It's impossible to know that.  You can design perfectly in-spec naughty
> servers breaking all of eglot tests.

Eglot shall fail the gracefully. The error messages I have seen so far
don't tell me anything.

> Or you can follow Eglot's maintainer advice to install versions of
> servers known to be working correctly.  Heroically complexifying Eglot
> to detect misbehaving servers is a completely futile exercise.

That's an illusion. People don't follow advices, people don't read
manuals. Believe me with 20+ years of Tramp experience, 40+ years
experience in developing and maintaining large projects.

> João

Best regards, Michael.