Fix off-by-one history pruning (bug#31211)

* lisp/subr.el (add-to-history): Clarify docstring.
Protect against negative history-length and unnecessary variable
modification, as per read_minibuf.

* lisp/ido.el (ido-record-command):
* lisp/international/mule-cmds.el (deactivate-input-method):
(set-language-environment-input-method):
* lisp/isearch.el (isearch-done):
* lisp/minibuffer.el (read-file-name-default):
* lisp/net/eww.el (eww-save-history):
* lisp/simple.el (edit-and-eval-command, repeat-complex-command):
(command-execute, kill-new, push-mark):
* src/callint.c (Fcall_interactively):
* src/minibuf.c (read_minibuf): Delegate to add-to-history.

* test/lisp/simple-tests.el (command-execute-prune-command-history):
* test/src/callint-tests.el
(call-interactively-prune-command-history): New tests.

2 files changed, 19 insertions, 0 deletions

diff --git a/test/lisp/simple-tests.el b/test/lisp/simple-tests.el
index 64b341bd469..7a10df20587 100644
--- a/test/lisp/simple-tests.el
+++ b/test/lisp/simple-tests.el
@@ -448,6 +448,17 @@ See Bug#21722."
         (call-interactively #'eval-expression)
         (should (equal (current-message) "66 (#o102, #x42, ?B)"))))))
 
+(ert-deftest command-execute-prune-command-history ()
+  "Check that Bug#31211 is fixed."
+  (let ((history-length 1)
+        (command-history ()))
+    (dotimes (_ (1+ history-length))
+      (command-execute "" t))
+    (should (= (length command-history) history-length))))
+
+
+;;; `line-number-at-pos'
+
 (ert-deftest line-number-at-pos-in-widen-buffer ()
   (let ((target-line 3))
     (with-temp-buffer
diff --git a/test/src/callint-tests.el b/test/src/callint-tests.el
index 9a812223ad0..feee9b692b7 100644
--- a/test/src/callint-tests.el
+++ b/test/src/callint-tests.el
@@ -43,4 +43,12 @@
                                          (list a b))))
                  '("a" "b"))))
 
+(ert-deftest call-interactively-prune-command-history ()
+  "Check that Bug#31211 is fixed."
+  (let ((history-length 1)
+        (command-history ()))
+    (dotimes (_ (1+ history-length))
+      (call-interactively #'ignore t))
+    (should (= (length command-history) history-length))))
+
 ;;; callint-tests.el ends here