bug#34294: 27.0.50; flymake-start-on-save-buffer has no effect

[Juri Linkov]

Hi João,

>> It looks good to me.  I just have a suggestion and would like
>> to see the commit msg, too.
>
> Please see the patch with the commit msg attached.

Could you please also push an additional patch that fixes
a race condition in flymake.  The problem is that currently
flymake starts even when flymake-mode is disabled.

Having such customization in ~/.emacs to not enable flymake-mode
in read-only buffers:

  (add-hook 'ruby-mode-hook
            (lambda ()
              (flymake-mode 1)
              (add-hook 'view-mode-hook
                        (lambda ()
                          (flymake-mode (if view-mode -1 1)))
                        nil t)))

It still runs flymake in read-only buffers because it disregards
the fact that flymake-mode becomes disabled before starting
flymake from post-command-hook or window-configuration-change-hook.

The fix is to check for flymake-mode again after hooks are finished:

diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index d6cd370dac..1c7823cb85 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -900,7 +904,7 @@ flymake-start
              (add-hook 'window-configuration-change-hook
                        #'start-on-display
                        'append 'local))
-            (t
+            (flymake-mode
              (setq flymake-check-start-time (float-time))
              (let ((backend-args
                     (and