Re: bug#1948: confusion and bug in dabbrev.el

[Alan Third <alan@idiocy.org>]

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Peter Tury said:
> However, the more serious problem is that it "forgets" such
> eliminations when it searches for `old' expansion in case of repeated
> calls of  `dabbrev-expand' (i.e. when the check "(eq last-command
> this-command)" in this function results t) what results in weird text
> in some cases.

I think I've got a fix for this.

The problem is that dabbrev--substitute-expansion alters EXPANSION
before using it in the substitution, but dabbrev-expand has no idea that
it's done this, so it assumes the unaltered EXPANSION is still valid and
saves it.

The patch makes dabbrev--substitute-expansion return EXPANSION, and
dabbrev-expand saves that version instead.

I considered making a new function to remove the whitespace and using it
in both dabbrev-expand and dabbrev--substitute-expansion, but returning
the value actually used strikes me as safer, in case anything else is
done to it.


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From 9ef22a911d58f772265bc1fde2608ea135a4dea2 Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sat, 30 Jan 2016 00:38:32 +0000
Subject: [PATCH] Always save the actual expansion

lisp/dabbrev.el (dabbrev--substitute-expansion): Return EXPANSION after
any processing.
lisp/dabbrev.el (dabbrev-expand): Set EXPANSION to the return value of
DABBREV--SUBSTITUTE-EXPANSION.
---
 lisp/dabbrev.el | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index 3557041..d9f36b1 100644
--- a/lisp/dabbrev.el
+++ b/lisp/dabbrev.el
@@ -546,8 +546,8 @@ dabbrev-expand
 		(copy-marker dabbrev--last-expansion-location)))
       ;; Success: stick it in and return.
       (setq buffer-undo-list (cons orig-point buffer-undo-list))
-      (dabbrev--substitute-expansion old abbrev expansion
-				     record-case-pattern)
+      (setq expansion (dabbrev--substitute-expansion old abbrev expansion
+                                                     record-case-pattern))
 
       ;; Save state for re-expand.
       (setq dabbrev--last-expansion expansion)
@@ -902,7 +902,9 @@ dabbrev--substitute-expansion
     ;; and (2) the replacement itself is all lower case.
     (dabbrev--safe-replace-match expansion
 				 (not use-case-replace)
-				 t)))
+				 t))
+  ;; Return the expansion actually used.
+  expansion)
 
 
 ;;;----------------------------------------------------------------
-- 
2.5.4 (Apple Git-61)


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-- 
Alan Third