master 5f12e288a5: Improve find-sibling-file error reporting

[Lars Ingebrigtsen]

branch: master
commit 5f12e288a51eb70e7d38a111d610cb09dfe04332
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Improve find-sibling-file error reporting
    
    * lisp/files.el (find-sibling-file): Improve error reporting.
---
 lisp/files.el | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/lisp/files.el b/lisp/files.el
index 97e58946bd..07ab2b45a5 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7303,16 +7303,22 @@ The \"sibling\" file is defined by the 
`find-sibling-rules' variable."
                  (unless buffer-file-name
                    (user-error "Not visiting a file"))
                  (list buffer-file-name)))
+  (unless find-sibling-rules
+    (user-error "The `find-sibling-rules' variable has not been configured"))
   (let ((siblings (find-sibling-file--search (expand-file-name file))))
-    (if (length= siblings 1)
-        (find-file (car siblings))
+    (cond
+     ((null siblings)
+      (user-error "Couldn't find any sibling files"))
+     ((length= siblings 1)
+      (find-file (car siblings)))
+     (t
       (let ((relatives (mapcar (lambda (sibling)
                                  (file-relative-name
                                   sibling (file-name-directory file)))
                                siblings)))
         (find-file
          (completing-read (format-prompt "Find file" (car relatives))
-                          relatives nil t nil nil (car relatives)))))))
+                          relatives nil t nil nil (car relatives))))))))
 
 (defun find-sibling-file--search (file)
   (let ((results nil))