Two issues with the new Flymake

[Lele Gaifax <lele@metapensiero.it>]

Hi all,

I'm happily using the new Flymake implementation coupled with the Python
backend (that I'm still hoping it could be merged into Emacs 26, see bug
#28808).

I have two "minor" issues with it, one I think should be corrected in Flymake,
the other by any chance related to my configuration, but was not able to
identify its source yet.

The first problem is something that happens when I add new code at the end of
the source: if I write something and then quickly enough partially delete it
with `delete-backward-char' and replace it with something else, at times
Flymake reports an error message about unexpected report from the backend; I
think it's due to the external checker reporting a problem in a region of the
buffer that isn't there anymore at the time Flymake receives/processes that
annotation. This is at worst a little annoyance, because at that time Emacs
"hangs" for a noticeable interval of time, enough to disrupt my (re)writing.

The second one is a strange interaction with the `python-shell-send-region' (a
feature that I use very seldom): when I execute that, I get the following
error message

   Error in post-command-hook (#[0
   "\304\305\303\242\306#\210r\302q\210\307\310\311\301\"\300\")\207" [nil
   (post-command on-display) #<killed buffer> (#0) remove-hook
   post-command-hook nil flymake-start remove post-command] 4]): (error
   "Selecting deleted buffer")

This does not happen in a `emacs -Q' session, so I bet it must be something
related to the activation of flymake-mode and/or with the python-flymake
backend, but as said despite my efforts I was not able to better understand
what's going on (toggle-debug-on-error didn't help). Do you have any advice on
how to investigate further?

Thanks in advance for any hint,
ciao, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.