(dabbrev--search): Don't downcase the result here.

(dabbrev-completion): Bind completion-ignore-case.
(dabbrev--substitute-expansion): Downcase the expansion here,
but not if case pattern matches start of original expansion.

1 files changed, 16 insertions, 2 deletions

diff --git a/lisp/dabbrev.el b/lisp/dabbrev.el
index ee3f1f55f29..7f8d1679103 100644
--- a/lisp/dabbrev.el
+++ b/lisp/dabbrev.el
@@ -340,7 +340,8 @@ if there is a suitable one already."
         (setq dabbrev--last-abbreviation abbrev)
         ;; Find all expansion
         (let ((completion-list
-               (dabbrev--find-all-expansions abbrev ignore-case-p)))
+               (dabbrev--find-all-expansions abbrev ignore-case-p))
+              (completion-ignore-case ignore-case-p))
           ;; Make an obarray with all expansions
           (setq my-obarray (make-vector (length completion-list) 0))
           (or (> (length my-obarray) 0)
@@ -749,6 +750,19 @@ See also `dabbrev-abbrev-char-regexp' and \\[dabbrev-completion]."
     (and nil use-case-replace
          (setq old (concat abbrev (or old "")))
          (setq expansion (concat abbrev expansion)))
+    ;; If the given abbrev is mixed case and its case pattern
+    ;; matches the start of the expansion,
+    ;; copy the expansion's case
+    ;; instead of downcasing all the rest.
+    (if (and (string= (or old abbrev)
+                      (substring expansion 0 (length (or old abbrev))))
+             (not (string= (or old abbrev)
+                           (downcase (or old abbrev))))
+             (not (string= (or old abbrev)
+                           (upcase (or old abbrev)))))
+        (setq use-case-replace nil)
+      (if use-case-replace
+          (setq expansion (downcase expansion))))
     (if old
         (save-excursion
           (search-backward old))
@@ -830,7 +844,7 @@ See also `dabbrev-abbrev-char-regexp' and \\[dabbrev-completion]."
               (setq dabbrev--last-table
                     (cons found-string dabbrev--last-table))
               (if (and ignore-case (eval dabbrev-case-replace))
-                  (downcase result)
+                  result
                 result)))))))
 
 (provide 'dabbrev)