Don't require isearch-update before isearch-done

It is useful to be able to call `isearch-done' unconditionally to
ensure a non-isearching state.

* lisp/isearch.el (isearch-done): Check that `isearch--current-buffer'
is a live buffer before using it (Bug #21091).
* test/lisp/isearch-tests.el (isearch--test-done): Test it.

2 files changed, 12 insertions, 3 deletions

diff --git a/lisp/isearch.el b/lisp/isearch.el
index b50379a250b..39ed8af3702 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -1045,9 +1045,10 @@ NOPUSH is t and EDIT is t."
   (remove-hook 'mouse-leave-buffer-hook 'isearch-done)
   (remove-hook 'kbd-macro-termination-hook 'isearch-done)
   (setq isearch-lazy-highlight-start nil)
-  (with-current-buffer isearch--current-buffer
-    (setq isearch--current-buffer nil)
-    (setq cursor-sensor-inhibit (delq 'isearch cursor-sensor-inhibit)))
+  (when (buffer-live-p isearch--current-buffer)
+    (with-current-buffer isearch--current-buffer
+      (setq isearch--current-buffer nil)
+      (setq cursor-sensor-inhibit (delq 'isearch cursor-sensor-inhibit))))
 
   ;; Called by all commands that terminate isearch-mode.
   ;; If NOPUSH is non-nil, we don't push the string on the search ring.
diff --git a/test/lisp/isearch-tests.el b/test/lisp/isearch-tests.el
index 48c342403c9..52f312d0b97 100644
--- a/test/lisp/isearch-tests.el
+++ b/test/lisp/isearch-tests.el
@@ -28,5 +28,13 @@
     (isearch-update)
     (should (equal isearch--current-buffer (current-buffer)))))
 
+(ert-deftest isearch--test-done ()
+  ;; Normal operation.
+  (isearch-update)
+  (isearch-done)
+  (should-not isearch--current-buffer)
+  ;; Bug #21091: let `isearch-done' work without `isearch-update'.
+  (isearch-done))
+
 (provide 'isearch-tests)
 ;;; isearch-tests.el ends here