bug#58389: 29.0.50; Python completion fails under certain conditions

[kobarity <kobarity@gmail.com>]

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I wrote:
> 
> I wrote:
> > I think `comint-snapshot-last-prompt' should not be called as long as 
> > `comint-output-filter' is not called and the Inferior Python Shell
> > buffer is not changed.  Attached is a patch to fix this issue.
> 
> Sorry, I was not aware of other processes using comint.  It might
> affect other processes.  I will reconsider the patch.

Attached is the revised patch to fix this issue.  Instead of
invalidating `comint-snapshot-last-prompt', I added codes to save and
restore the buffer local variable `comint-last-prompt-overlay' or
`comint-last-prompt'.

Best Regards,

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From 5962306d13d77aac25e0d991e8aaaab34d499c86 Mon Sep 17 00:00:00 2001
From: kobarity <kobarity@gmail.com>
Date: Mon, 10 Oct 2022 22:24:17 +0900
Subject: [PATCH] Fix Python completion failure under certain conditions

* lisp/progmodes/python.el (python-shell-send-string-no-output):
Save and restore `comint-last-prompt-overlay' or `comint-last-prompt'.
* test/lisp/progmodes/python-tests.el (python-tests-shell-wait-for-prompt):
New helper function.
(python-tests-with-temp-buffer-with-shell): New helper macro.
(python-shell-completion-1, python-shell-completion-native-1)
(python-shell-completion-native-with-ffap-1)
(python-shell-completion-native-with-eldoc-1): New tests (bug#58389).
---
 lisp/progmodes/python.el            | 26 +++++---
 test/lisp/progmodes/python-tests.el | 93 +++++++++++++++++++++++++++++
 2 files changed, 111 insertions(+), 8 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 80c5b31b6e..680b57fc3e 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -3413,15 +3413,25 @@ python-shell-send-string-no-output
   "Send STRING to PROCESS and inhibit output.
 Return the output."
   (or process (setq process (python-shell-get-process-or-error)))
-  (cl-letf (((process-filter process)
-             (lambda (_proc str)
-               (with-current-buffer (process-buffer process)
-                 (python-shell-output-filter str))))
-            (python-shell-output-filter-in-progress t)
-            (inhibit-quit t))
+  (cl-letf* (((process-filter process)
+              (lambda (_proc str)
+                (with-current-buffer (process-buffer process)
+                  (python-shell-output-filter str))))
+             (python-shell-output-filter-in-progress t)
+             (inhibit-quit t)
+             (buffer (process-buffer process))
+             (last-prompt (cond ((boundp 'comint-last-prompt-overlay)
+                                 'comint-last-prompt-overlay)
+                                ((boundp 'comint-last-prompt)
+                                 'comint-last-prompt)))
+             (last-prompt-value (buffer-local-value last-prompt buffer)))
     (or
      (with-local-quit
-       (python-shell-send-string string process)
+       (unwind-protect
+           (python-shell-send-string string process)
+         (when (not (null last-prompt))
+           (with-current-buffer buffer
+             (set last-prompt last-prompt-value))))
        (while python-shell-output-filter-in-progress
          ;; `python-shell-output-filter' takes care of setting
          ;; `python-shell-output-filter-in-progress' to NIL after it
@@ -3430,7 +3440,7 @@ python-shell-send-string-no-output
        (prog1
            python-shell-output-filter-buffer
          (setq python-shell-output-filter-buffer nil)))
-     (with-current-buffer (process-buffer process)
+     (with-current-buffer buffer
        (comint-interrupt-subjob)))))
 
 (defun python-shell-internal-send-string (string)
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index fdaedb5fd7..60ff9bb613 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -43,6 +43,37 @@ python-tests-with-temp-buffer
        (goto-char (point-min))
        ,@body)))
 
+(defun python-tests-shell-wait-for-prompt ()
+  "Wait for the prompt in the shell buffer."
+  (python-shell-with-shell-buffer
+    (while (not (if-let ((prompt (python-util-comint-last-prompt)))
+                    (python-shell-comint-end-of-output-p
+                     (buffer-substring-no-properties
+                      (car prompt) (cdr prompt)))))
+      (sit-for 0.1))))
+
+(defmacro python-tests-with-temp-buffer-with-shell (contents &rest body)
+  "Create a `python-mode' enabled temp buffer with CONTENTS and `run-python'.
+BODY is code to be executed within the temp buffer.  Point is
+always located at the beginning of buffer.  Native completion is
+turned off.  Shell buffer will be killed on exit."
+  (declare (indent 1) (debug t))
+  `(with-temp-buffer
+     (let ((python-indent-guess-indent-offset nil)
+           (python-shell-completion-native-enable nil))
+       (python-mode)
+       (unwind-protect
+           (progn
+             (run-python nil t)
+             (insert ,contents)
+             (goto-char (point-min))
+             (python-tests-shell-wait-for-prompt)
+             ,@body)
+         (when (python-shell-get-buffer)
+           (python-shell-with-shell-buffer
+             (let (kill-buffer-hook kill-buffer-query-functions)
+               (kill-buffer))))))))
+
 (defmacro python-tests-with-temp-file (contents &rest body)
   "Create a `python-mode' enabled file with CONTENTS.
 BODY is code to be executed within the temp buffer.  Point is
@@ -4365,6 +4396,68 @@ python-shell-completion-native-interpreter-disabled-p-1
          (python-shell-interpreter "/some/path/to/bin/pypy"))
     (should (python-shell-completion-native-interpreter-disabled-p))))
 
+(ert-deftest python-shell-completion-1 ()
+  (skip-unless (executable-find python-tests-shell-interpreter))
+  (python-tests-with-temp-buffer-with-shell
+   "
+import abc
+"
+   (let ((inhibit-message t))
+     (python-shell-send-buffer)
+     (python-tests-shell-wait-for-prompt)
+     (goto-char (point-max))
+     (insert "abc.")
+     (should (completion-at-point))
+     (insert "A")
+     (should (completion-at-point)))))
+
+(ert-deftest python-shell-completion-native-1 ()
+  (skip-unless (executable-find python-tests-shell-interpreter))
+  (python-tests-with-temp-buffer-with-shell
+   "
+import abc
+"
+   (let ((inhibit-message t))
+     (python-shell-completion-native-turn-on)
+     (python-shell-send-buffer)
+     (python-tests-shell-wait-for-prompt)
+     (goto-char (point-max))
+     (insert "abc.")
+     (should (completion-at-point))
+     (insert "A")
+     (should (completion-at-point)))))
+
+(ert-deftest python-shell-completion-native-with-ffap-1 ()
+  (skip-unless (executable-find python-tests-shell-interpreter))
+  (python-tests-with-temp-buffer-with-shell
+   "
+import abc
+"
+   (let ((inhibit-message t))
+     (python-shell-completion-native-turn-on)
+     (python-shell-send-buffer)
+     (python-tests-shell-wait-for-prompt)
+     (goto-char (point-max))
+     (insert "abc.")
+     ;; This is called when FFAP is enabled and a find-file function is called.
+     (python-ffap-module-path "abc.")
+     (should (completion-at-point)))))
+
+(ert-deftest python-shell-completion-native-with-eldoc-1 ()
+  (skip-unless (executable-find python-tests-shell-interpreter))
+  (python-tests-with-temp-buffer-with-shell
+   "
+import abc
+"
+   (let ((inhibit-message t))
+     (python-shell-completion-native-turn-on)
+     (python-shell-send-buffer)
+     (python-tests-shell-wait-for-prompt)
+     (goto-char (point-max))
+     (insert "abc.")
+     ;; This is called by idle-timer when ElDoc is enabled.
+     (python-eldoc-function)
+     (should (completion-at-point)))))
 
 
 \f
-- 
2.34.1