Add a test for let-binding unwinding

Bindings in other buffers are not un-set when we unwind a let-binding
which set the default value.  There doesn't seem to be an existing
test which covers this, so here's one.

* test/src/data-tests.el (data-tests--let-buffer-local-no-unwind-other-buffers):
  Add test for let-binding unwinding behavior

1 files changed, 22 insertions, 0 deletions

diff --git a/test/src/data-tests.el b/test/src/data-tests.el
index 03d867f18a8..d0cb87293f0 100644
--- a/test/src/data-tests.el
+++ b/test/src/data-tests.el
@@ -364,6 +364,28 @@ comparing the subr with a much slower lisp implementation."
           (should (equal (default-value var) (symbol-value var))))
         (should (equal (default-value var) def))))))
 
+(ert-deftest data-tests--let-buffer-local-no-unwind-other-buffers ()
+  "Test that a let-binding for a buffer-local unwinds only current-buffer."
+  (let ((blvar (make-symbol "blvar")))
+    (set-default blvar 0)
+    (make-variable-buffer-local blvar)
+    (dolist (var (list blvar 'left-margin))
+      (let* ((def (default-value var))
+             (newdef (+ def 1))
+             (otherbuf (generate-new-buffer "otherbuf")))
+        (with-temp-buffer
+          (cl-progv (list var) (list newdef)
+            (with-current-buffer otherbuf
+              (set var 123)
+              (should (local-variable-p var))
+              (should (equal (symbol-value var) 123))
+              (should (equal (default-value var) newdef))))
+          (with-current-buffer otherbuf
+            (should (local-variable-p var))
+            (should (equal (symbol-value var) 123))
+            (should (equal (default-value var) def)))
+          )))))
+
 (ert-deftest binding-test-makunbound ()
   "Tests of makunbound, from the manual."
   (with-current-buffer binding-test-buffer-B