master 7d39453fd6 1/2: Add new predicate list-of-strings-p

[Lars Ingebrigtsen]

branch: master
commit 7d39453fd64e355526291b0ca5672e838de5fb58
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Add new predicate list-of-strings-p
    
    * lisp/subr.el (list-of-strings-p): New function.
---
 lisp/subr.el            | 5 +++++
 test/lisp/subr-tests.el | 7 +++++++
 2 files changed, 12 insertions(+)

diff --git a/lisp/subr.el b/lisp/subr.el
index bfc2e207b2..e8e8f1584b 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -4026,6 +4026,11 @@ system's shell."
 Otherwise, return nil."
   (or (stringp object) (null object)))
 
+(defun list-of-strings-p (object)
+  "Return t if OBJECT is nil or a list of strings."
+  (and (listp object)
+       (seq-every-p #'stringp object)))
+
 (defun booleanp (object)
   "Return t if OBJECT is one of the two canonical boolean values: t or nil.
 Otherwise, return nil."
diff --git a/test/lisp/subr-tests.el b/test/lisp/subr-tests.el
index 3011713210..38966cea58 100644
--- a/test/lisp/subr-tests.el
+++ b/test/lisp/subr-tests.el
@@ -1158,5 +1158,12 @@ final or penultimate step during initialization."))
       (should (equal (butlast l n)
                      (subr-tests--butlast-ref l n))))))
 
+(ert-deftest test-list-of-strings-p ()
+  (should-not (list-of-strings-p 1))
+  (should (list-of-strings-p nil))
+  (should (list-of-strings-p '("a" "b")))
+  (should-not (list-of-strings-p ["a" "b"]))
+  (should-not (list-of-strings-p '("a" nil "b"))))
+
 (provide 'subr-tests)
 ;;; subr-tests.el ends here