bug#40529: 26.3; global-display-line-numbers-mode and flymake-show-diagnostics-buffer error

[Eli Zaretskii]

> From: Aidan Beggs <nadiasggeb001@gmail.com>
> Date: Thu, 9 Apr 2020 16:55:44 -0400
> 
> emacs -Q
> C-x b *scratch*
> M-x global-display-line-numbers-mode
> M-x flymake-mode
> M-x flymake-show-diagnostics-buffer

João, here are the results of my preliminary investigation into this,
as posted on Reddit (where this was first reported), I hope they will
be helpful:

  Under the above settings, flymake--diagnostics-buffer-entries is
  invoked as side effect of calling flymake-diagnostics-buffer-mode from
  flymake-show-diagnostics-buffer, and at that point
  flymake--diagnostics-buffer-source has not yet been set to a valid
  buffer name.  So the with-current-buffer form at the beginning of
  flymake--diagnostics-buffer-entries barfs.

Thanks.