Merge from origin/emacs-27

ac3da1dd96 Handle project--files-in-directory finding no files better
650a664ccd Let imenu to work on the menu bar when its list is a singl...

3 files changed, 12 insertions, 5 deletions

diff --git a/lisp/imenu.el b/lisp/imenu.el
index fb8b3de662b..1949f2f48f7 100644
--- a/lisp/imenu.el
+++ b/lisp/imenu.el
@@ -911,11 +911,15 @@ to `imenu-update-menubar'.")
         (setq index-alist (imenu--split-submenus index-alist))
         (let* ((menu (imenu--split-menu index-alist
                                         (buffer-name)))
-               (menu1 (imenu--create-keymap (car menu)
-                                            (cdr (if (< 1 (length (cdr menu)))
-                                                     menu
-                                                   (car (cdr menu))))
-                                            'imenu--menubar-select)))
+               (menu1 (imenu--create-keymap
+                       (car menu)
+                       (cdr (if (or (< 1 (length (cdr menu)))
+                                    ;; Have we a non-nested single entry?
+                                    (atom (cdadr menu))
+                                    (atom (cadadr menu)))
+                                menu
+                              (car (cdr menu))))
+                       'imenu--menubar-select)))
           (setcdr imenu--menubar-keymap (cdr menu1)))))))
 
 (defun imenu--menubar-select (item)
diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index f4678681858..1f4cbe96ad8 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -480,6 +480,8 @@ pattern to search for."
      nil)))
 
 (defun project--find-regexp-in-files (regexp files)
+  (unless files
+    (user-error "Empty file list"))
   (let ((xrefs (xref-matches-in-files regexp files)))
     (unless xrefs
       (user-error "No matches for: %s" regexp))
diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 1a344563405..c36a9bd9940 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -1232,6 +1232,7 @@ IGNORES is a list of glob patterns for files to ignore."
   "Find all matches for REGEXP in FILES.
 Return a list of xref values.
 FILES must be a list of absolute file names."
+  (cl-assert (consp files))
   (pcase-let*
       ((output (get-buffer-create " *project grep output*"))
        (`(,grep-re ,file-group ,line-group . ,_) (car grep-regexp-alist))