Allow passing unknown specs to format-spec

* lisp/format-spec.el (format-spec): Allow passing through format
strings that have no specs (to be able to act as a filter).  Also
add an example.
* test/lisp/format-spec-tests.el (test-format-spec): Add tests for
the new functionality.

1 files changed, 11 insertions, 1 deletions

diff --git a/test/lisp/format-spec-tests.el b/test/lisp/format-spec-tests.el
index a5c62ac9ce3..e831657a3e6 100644
--- a/test/lisp/format-spec-tests.el
+++ b/test/lisp/format-spec-tests.el
@@ -23,11 +23,21 @@
 (require 'format-spec)
 
 (ert-deftest test-format-spec ()
-  (should (equal (format-spec "foo %b zot" '((?b . "bar")))
+  (should (equal (format-spec "foo %b zot" `((?b . "bar")))
                  "foo bar zot"))
   (should (equal (format-spec "foo %-10b zot" '((?b . "bar")))
                  "foo bar        zot"))
   (should (equal (format-spec "foo %10b zot" '((?b . "bar")))
                  "foo        bar zot")))
 
+(ert-deftest test-format-unknown ()
+  (should (eq (condition-case _
+                  (format-spec "foo %b %z zot" '((?b . "bar")))
+                (error :error))
+              :error))
+  (should (equal (format-spec "foo %b %z zot" '((?b . "bar")) t)
+                 "foo bar %z zot"))
+  (should (equal (format-spec "foo %b %z %% zot" '((?b . "bar")) t)
+                 "foo bar %z %% zot")))
+
 ;;; format-spec-tests.el ends here