[PATCH] Handle case where `beg` and `end` are strings instead of markers

[James N. V. Cash]

With the changes to pass affixes to the completion functions, the
begin and end points passed to the completion function are now
sometimes strings instead of numbers or markers. This handles that
case by searching for said prefix and suffix.

Without this, completion functions that call `completion--replace` error
out -- for example, completing tags in org-mode.

---
 lisp/minibuffer.el | 69 +++++++++++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 29 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index ef71b4e6be..d75b771044 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1147,35 +1147,46 @@ completion--replace
                               newtext)
     ;; Remove all text properties.
     (set-text-properties 0 (length newtext) nil newtext))
-  ;; Maybe this should be in subr.el.
-  ;; You'd think this is trivial to do, but details matter if you want
-  ;; to keep markers "at the right place" and be robust in the face of
-  ;; after-change-functions that may themselves modify the buffer.
-  (let ((prefix-len 0))
-    ;; Don't touch markers in the shared prefix (if any).
-    (while (and (< prefix-len (length newtext))
-                (< (+ beg prefix-len) end)
-                (eq (char-after (+ beg prefix-len))
-                    (aref newtext prefix-len)))
-      (setq prefix-len (1+ prefix-len)))
-    (unless (zerop prefix-len)
-      (setq beg (+ beg prefix-len))
-      (setq newtext (substring newtext prefix-len))))
-  (let ((suffix-len 0))
-    ;; Don't touch markers in the shared suffix (if any).
-    (while (and (< suffix-len (length newtext))
-                (< beg (- end suffix-len))
-                (eq (char-before (- end suffix-len))
-                    (aref newtext (- (length newtext) suffix-len 1))))
-      (setq suffix-len (1+ suffix-len)))
-    (unless (zerop suffix-len)
-      (setq end (- end suffix-len))
-      (setq newtext (substring newtext 0 (- suffix-len))))
-    (goto-char beg)
-    (let ((length (- end beg)))         ;Read `end' before we insert the text.
-      (insert-and-inherit newtext)
-      (delete-region (point) (+ (point) length)))
-    (forward-char suffix-len)))
+  (let ((beg (if (number-or-marker-p beg)
+                 beg
+               (save-excursion
+                 (goto-char (minibuffer-prompt-end))
+                 (+ (search-forward beg)
+                    (length beg)))))
+        (end (if (number-or-marker-p end)
+                 end
+               (save-excursion
+                 (goto-char (point-max))
+                 (search-backward end)))))
+    ;; Maybe this should be in subr.el.
+    ;; You'd think this is trivial to do, but details matter if you want
+    ;; to keep markers "at the right place" and be robust in the face of
+    ;; after-change-functions that may themselves modify the buffer.
+    (let ((prefix-len 0))
+      ;; Don't touch markers in the shared prefix (if any).
+      (while (and (< prefix-len (length newtext))
+                  (< (+ beg prefix-len) end)
+                  (eq (char-after (+ beg prefix-len))
+                      (aref newtext prefix-len)))
+        (setq prefix-len (1+ prefix-len)))
+      (unless (zerop prefix-len)
+        (setq beg (+ beg prefix-len))
+        (setq newtext (substring newtext prefix-len))))
+    (let ((suffix-len 0))
+      ;; Don't touch markers in the shared suffix (if any).
+      (while (and (< suffix-len (length newtext))
+                  (< beg (- end suffix-len))
+                  (eq (char-before (- end suffix-len))
+                      (aref newtext (- (length newtext) suffix-len 1))))
+        (setq suffix-len (1+ suffix-len)))
+      (unless (zerop suffix-len)
+        (setq end (- end suffix-len))
+        (setq newtext (substring newtext 0 (- suffix-len))))
+      (goto-char beg)
+      (let ((length (- end beg)))         ;Read `end' before we insert the 
text.
+        (insert-and-inherit newtext)
+        (delete-region (point) (+ (point) length)))
+      (forward-char suffix-len))))

 (defcustom completion-cycle-threshold nil
   "Number of completion candidates below which cycling is used.
--
2.25.1