bug#30813: 26.0.91; flyspell does not recheck after transpose-chars

[Aaron Jensen <aaronjensen@gmail.com>]

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On Tue, Mar 13, 2018 at 10:59 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> Transposing words can create duplicate words, or fix word duplication, something
> that flyspell flags as well.

I see. There are lots of ways to break this--change the first instance
of the word in any way and the second word does not notice. It seems
like if that were to be addressed it would need to be something that
is command agnostic. Perhaps something like looking at the next word
to see if it is currently marked duplicate and if so rechecking.

In the meantime, how about the attached patch which addresses just
transpose-chars?

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From d88101f30e1ddfb5fb39170c553f854758f7b1d2 Mon Sep 17 00:00:00 2001
From: Aaron Jensen <aaronjensen@gmail.com>
Date: Wed, 14 Mar 2018 08:09:50 -0700
Subject: [PATCH] Enable flyspell to check word point was at before
 transpose-chars

* lisp/textmodes/flyspell.el (flyspell-post-command-hook): Check word
  before previous point location after transpose-chars. (Bug#30813)
---
 lisp/textmodes/flyspell.el | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lisp/textmodes/flyspell.el b/lisp/textmodes/flyspell.el
index e462669626..b5c841403a 100644
--- a/lisp/textmodes/flyspell.el
+++ b/lisp/textmodes/flyspell.el
@@ -982,6 +982,11 @@ flyspell-post-command-hook
       (let ((command this-command)
             ;; Prevent anything we do from affecting the mark.
             deactivate-mark)
+        (if (and (eq command 'transpose-chars)
+                 flyspell-pre-point)
+            (save-excursion
+              (goto-char (- flyspell-pre-point 1))
+              (flyspell-word)))
         (if (flyspell-check-pre-word-p)
             (save-excursion
               '(flyspell-debug-signal-pre-word-checked)
-- 
2.15.1