bug#17558: 24.4.50; global-subword-mode breaks ERC

[Dima Kogan]

Daniel Colascione <dancol@dancol.org> writes:

> On 05/23/2014 02:19 AM, Dima Kogan wrote:
>> Hi. I'm using a very recent build of emacs from the VCS. With this build
>> ERC gets very confused if global-subword-mode is on. I believe it worked
>> fine just a few months ago.
>> 
>> Recipe:
>> 
>> 1. emacs -Q
>> 2. (global-subword-mode)
>> 3. M-x erc
>> 4. Default values for the server, nickname, password, etc are fine to
>> show the issue
>
> Thanks for the repro. This bug is probably due to my changing how
> subword-mode works: now, forward-word will stop at subword boundaries,
> and I'm guessing ERC was relying on the old behavior. I can try to take
> a look at it if nobody who knows ERC better wants to try first.

Here's a patch. It works, but I don't like how un-future-proof it is. An
uncareful coder can simply use (forward-word) somewhere and get things
to break again. Is there a better way?

>From 655e7b9b5735bd62aac104645b5a224636ab97ff Mon Sep 17 00:00:00 2001
From: Dima Kogan <dima@secretsauce.net>
Date: Tue, 30 Dec 2014 23:29:21 -0800
Subject: [PATCH] ERC no longer gets confused by subword-mode

In commit 6ddc44225e743e2b2a0d5c192f50aefd7a4a915b subword-mode was
integrated into the syntax table instead of simply remapping the
interactive motion bindings as was done previously.  This had the
unintended effect of changing the behavior of lisp programs that touch
words.  In the case of ERC, it completely broke it: emacs now throws an
error when ERC is launched, making it unusable when subword-mode is
active.

This commit temporarily disables subword-mode so that ERC functions that
touch words do so the "normal" way.

Closes: #17558
---
 lisp/erc/erc-backend.el |  9 ++++++++-
 lisp/erc/erc-button.el  | 23 +++++++++++++++--------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index bedb20f..fa95d7e 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -480,7 +480,14 @@ Currently this is called by `erc-send-input'."
   (with-temp-buffer
     (insert str)
     (goto-char (point-min))
-    (upcase-word 1)
+
+    ;; If we're in subword-mode then functions operating on words act
+    ;; differently. Here I temporarily disable subword-mode before
+    ;; touching the words
+    (let ((find-word-boundary-function-table
+           (if (boundp 'subword-empty-char-table)
+               subword-empty-char-table find-word-boundary-function-table)))
+      (upcase-word 1))
     (buffer-string)))
 
 (defun erc-server-setup-periodical-ping (buffer)
diff --git a/lisp/erc/erc-button.el b/lisp/erc/erc-button.el
index 10e7318..8343425 100644
--- a/lisp/erc/erc-button.el
+++ b/lisp/erc/erc-button.el
@@ -300,14 +300,21 @@ specified by `erc-button-alist'."
     (when (or (eq t form)
               (eval form))
       (goto-char (point-min))
-      (while (forward-word 1)
-        (setq bounds (bounds-of-thing-at-point 'word))
-        (setq word (buffer-substring-no-properties
-                    (car bounds) (cdr bounds)))
-        (when (or (and (erc-server-buffer-p) (erc-get-server-user word))
-                  (and erc-channel-users (erc-get-channel-user word)))
-          (erc-button-add-button (car bounds) (cdr bounds)
-                                 fun t (list word)))))))
+
+      ;; If we're in subword-mode then functions operating on words
+      ;; act differently. Here I temporarily disable subword-mode
+      ;; before touching the words
+      (let ((find-word-boundary-function-table
+             (if (boundp 'subword-empty-char-table)
+                 subword-empty-char-table find-word-boundary-function-table)))
+        (while (forward-word 1)
+          (setq bounds (bounds-of-thing-at-point 'word))
+          (setq word (buffer-substring-no-properties
+                      (car bounds) (cdr bounds)))
+          (when (or (and (erc-server-buffer-p) (erc-get-server-user word))
+                    (and erc-channel-users (erc-get-channel-user word)))
+            (erc-button-add-button (car bounds) (cdr bounds)
+                                   fun t (list word))))))))
 
 (defun erc-button-add-buttons-1 (regexp entry)
   "Search through the buffer for matches to ENTRY and add buttons."
-- 
2.1.3