bug#69809: 30.0.50; flymake: error in process sentinel

[Spencer Baugh <sbaugh@janestreet.com>]

Eli Zaretskii <eliz@gnu.org> writes:
>> From: Eshel Yaron <me@eshelyaron.com>
>> Cc: sbaugh@catern.com,  Spencer Baugh <sbaugh@janestreet.com>,  Eli
>>  Zaretskii <eliz@gnu.org>,  69809@debbugs.gnu.org
>> Date: Thu, 11 Jul 2024 13:15:41 +0200
>> 
>> Eshel Yaron <me@eshelyaron.com> writes:
>> 
>> [...]
>> 
>> > This issue bothered me as well.  Here's a recipe for reproducing on
>> > master, with emacs -Q:
>> >
>> > 1. (add-hook 'c-mode-hook 'flymake-mode)
>> > 2. (add-hook 'c-mode-hook 'eglot-ensure)
>> > 3. Find some C file
>> >
>> > This happens because Eglot _restarts_ flymake-mode while flymake-cc's
>> > process is already running.  Here's a simple fix:
>> >
>> > diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
>> > index a893a8d749a..c9e1bb7b52d 100644
>> > --- a/lisp/progmodes/eglot.el
>> > +++ b/lisp/progmodes/eglot.el
>> > @@ -2040,7 +2040,7 @@ eglot--managed-mode
>> >      (unless (eglot--stay-out-of-p 'imenu)
>> >        (add-function :before-until (local 'imenu-create-index-function)
>> >                      #'eglot-imenu))
>> > -    (unless (eglot--stay-out-of-p 'flymake) (flymake-mode 1))
>> > +    (unless (or (eglot--stay-out-of-p 'flymake) flymake-mode) (flymake-mode 1))
>> >      (unless (eglot--stay-out-of-p 'eldoc)
>> >        (add-hook 'eldoc-documentation-functions #'eglot-hover-eldoc-function
>> >                  nil t)
>> 
>> I realized that the change above has the downside of no longer
>> immediately initiating a Flymake analysis with Eglot in place.  To
>> preserve that behavior, maybe something like the following is better:
>> 
>> diff --git a/lisp/progmodes/eglot.el b/lisp/progmodes/eglot.el
>> index a893a8d749a..6cd48917d47 100644
>> --- a/lisp/progmodes/eglot.el
>> +++ b/lisp/progmodes/eglot.el
>> @@ -2040,7 +2040,8 @@ eglot--managed-mode
>>      (unless (eglot--stay-out-of-p 'imenu)
>>        (add-function :before-until (local 'imenu-create-index-function)
>>                      #'eglot-imenu))
>> -    (unless (eglot--stay-out-of-p 'flymake) (flymake-mode 1))
>> +    (unless (eglot--stay-out-of-p 'flymake)
>> +      (if flymake-mode (flymake-start) (flymake-mode 1)))
>>      (unless (eglot--stay-out-of-p 'eldoc)
>>        (add-hook 'eldoc-documentation-functions #'eglot-hover-eldoc-function
>>                  nil t)
>
> Spencer, any comments?
>
> From where I stand, this is okay for the emacs-30 release branch,
> unless you think it could break some legitimate workflow.

Yes, this seems good for emacs-30.  Thanks Eshel!