Fix Python PDB tracking for remote inferior Python

* lisp/progmodes/python.el (python-shell-local-prefix): New
constant.
(python-shell--convert-file-name-to-send): New function to
add/remove prefix.
(python-shell-send-string, python-shell-send-file): Changed to
use 'python-shell--convert-file-name-to-send'.
(python-pdbtrack-set-tracked-buffer): Changed to add/remove
prefix.
* test/lisp/progmodes/python-tests.el
(python-shell--convert-file-name-to-send-1): New test.
(Bug#79036)

lisp/progmodes/python.el

@@ -3698,6 +3698,10 @@ def __PYTHON_EL_eval_file(filename, tempname, delete):
   "Code used to evaluate files in inferior Python processes.
 The coding cookie regexp is specified in PEP 263.")
 
+(defconst python-shell-local-prefix "/local:"
+  "A prefix used to indicate that a file is local.
+It is used when sending file names to remote Python processes.")
+
 (defun python-shell-comint-watch-for-first-prompt-output-filter (output)
   "Run `python-shell-first-prompt-hook' when first prompt is found in OUTPUT."
   (when (not python-shell--first-prompt-received)
@@ -4016,6 +4020,27 @@ there for compatibility with CEDET.")
         (signal 'wrong-type-argument (list 'stringp text)))))
   "Encode TEXT as a valid Python string.")
 
+(defun python-shell--convert-file-name-to-send (process file-name)
+  "Convert the FILE-NAME for sending to the inferior Python PROCESS.
+If PROCESS is local and FILE-NAME is prefixed with
+`python-shell-local-prefix', remove the prefix.  If PROCESS is remote
+and the FILE-NAME is not prefixed, prepend `python-shell-local-prefix'.
+If PROCESS is remote and the file is on the same remote host, remove the
+remote prefix.  Otherwise, return the file name as is."
+  (when file-name
+    (let ((process-prefix
+           (file-remote-p
+            (with-current-buffer (process-buffer process) default-directory)))
+          (local-prefix (string-prefix-p python-shell-local-prefix file-name)))
+      (cond
+       ((and (not process-prefix) local-prefix)
+        (string-remove-prefix python-shell-local-prefix file-name))
+       ((and process-prefix (not (or local-prefix (file-remote-p file-name))))
+        (concat python-shell-local-prefix (file-local-name file-name)))
+       ((and process-prefix (string= (file-remote-p file-name) process-prefix))
+        (file-local-name file-name))
+       (t file-name)))))
+
 (defun python-shell-send-string (string &optional process msg)
   "Send STRING to inferior Python PROCESS.
 When optional argument MSG is non-nil, forces display of a
@@ -4023,11 +4048,13 @@ user-friendly message if there's no process running; defaults to
 t when called interactively."
   (interactive
    (list (read-string "Python command: ") nil t))
-  (let ((process (or process (python-shell-get-process-or-error msg)))
+  (let* ((process (or process (python-shell-get-process-or-error msg)))
-        (code (format "__PYTHON_EL_eval(%s, %s)\n"
+         (code (format "__PYTHON_EL_eval(%s, %s)\n"
-                      (python-shell--encode-string string)
+                       (python-shell--encode-string string)
-                      (python-shell--encode-string (or (buffer-file-name)
+                       (python-shell--encode-string
-                                                       "<string>")))))
+                        (or (python-shell--convert-file-name-to-send
+                             process (buffer-file-name))
+                            "<string>")))))
     (unless python-shell-output-filter-in-progress
       (with-current-buffer (process-buffer process)
         (save-excursion
@@ -4358,7 +4385,8 @@ t when called interactively."
             temp-file-name (with-temp-buffer
                              (insert-file-contents file-name)
                              (python-shell--save-temp-file (current-buffer))))))
-  (let* ((file-name (file-local-name (expand-file-name file-name)))
+  (let* ((file-name (python-shell--convert-file-name-to-send
+                     process (expand-file-name file-name)))
          (temp-file-name (when temp-file-name
                            (file-local-name (expand-file-name
                                              temp-file-name)))))
@@ -5082,8 +5110,12 @@ Never set this variable directly, use
   "Set the buffer for FILE-NAME as the tracked buffer.
 Internally it uses the `python-pdbtrack-tracked-buffer' variable.
 Returns the tracked buffer."
-  (let* ((file-name-prospect (concat (file-remote-p default-directory)
+  (let* ((file-name-prospect
-                              file-name))
+          (if (string-prefix-p python-shell-local-prefix file-name)
+              (string-remove-prefix python-shell-local-prefix file-name)
+            (if (file-remote-p file-name)
+                file-name
+              (concat (file-remote-p default-directory) file-name))))
          (file-buffer (get-file-buffer file-name-prospect)))
     (unless file-buffer
       (cond

test/lisp/progmodes/python-tests.el

@@ -4602,6 +4602,32 @@ and `python-shell-interpreter-args' in the new shell buffer."
                             "^\\(o\\.t \\|\\)")))
        (ignore-errors (delete-file startup-file))))))
 
+(ert-deftest python-shell--convert-file-name-to-send-1 ()
+  "Test parameters consist of a list of the following three elements.
+1. The variable `default-directory' of the process.
+2. FILE-NAME argument.
+3. The expected return value."
+  (python-tests-with-temp-buffer-with-shell
+   ""
+   (let* ((path "/tmp/tmp.py")
+          (local-path (concat python-shell-local-prefix path))
+          (remote1-path (concat "/ssh:remote1:" path))
+          (remote2-path (concat "/ssh:remote2:" path))
+          (process (python-shell-get-process)))
+     (dolist
+         (test (list (list "/tmp" nil nil)
+                     (list "/tmp" path path)
+                     (list "/tmp" local-path path)
+                     (list "/ssh:remote1:/tmp" path local-path)
+                     (list "/ssh:remote1:/tmp" local-path local-path)
+                     (list "/ssh:remote1:/tmp" remote1-path path)
+                     (list "/ssh:remote1:/tmp" remote2-path remote2-path)))
+       (with-current-buffer (process-buffer process)
+         (setq default-directory (nth 0 test)))
+       (should (string= (python-shell--convert-file-name-to-send
+                         process (nth 1 test))
+                        (nth 2 test)))))))
+
 (ert-deftest python-shell-buffer-substring-1 ()
   "Selecting a substring of the whole buffer must match its contents."
   (python-tests-with-temp-buffer