Performance improvement of 'python-shell-get-process'

'python-shell-get-process' is frequently called from
'python-eldoc--get-doc-at-point' and etc., invoking
'project-current' unless there is a buffer-specific Inferior
Python process.  When the buffer is a remote buffer not
belonging to any project and has significant latency,
'project-current' may take a long time.  To avoid this,
implement a process cache in 'python-shell-get-process'.

* lisp/progmodes/python.el (python-shell--process-cache)
(python-shell--process-cache-valid): New variables.
(python-shell--invalidate-process-cache): New function.
(python-shell-make-comint): Add a call to the above function.
(python-shell-get-process): Add process cache.  (Bug#80045)

1 files changed, 20 insertions, 1 deletions

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 5a820f05d77..848a26229e6 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -3816,6 +3816,16 @@ variable.
   (compilation-shell-minor-mode 1)
   (python-pdbtrack-setup-tracking))
 
+(defvar-local python-shell--process-cache)
+(defvar-local python-shell--process-cache-valid)
+
+(defun python-shell--invalidate-process-cache ()
+  "Invalidate process cache."
+  (dolist (buffer (buffer-list))
+    (with-current-buffer buffer
+      (setq python-shell--process-cache nil
+            python-shell--process-cache-valid nil))))
+
 (defun python-shell-make-comint (cmd proc-name &optional show internal)
   "Create a Python shell comint buffer.
 CMD is the Python command to be executed and PROC-NAME is the
@@ -3832,6 +3842,7 @@ killed."
       (let* ((proc-buffer-name
               (format (if (not internal) "*%s*" " *%s*") proc-name)))
         (when (not (comint-check-proc proc-buffer-name))
+          (python-shell--invalidate-process-cache)
           (let* ((cmdlist (split-string-and-unquote cmd))
                  (interpreter (car cmdlist))
                  (args (cdr cmdlist))
@@ -3955,7 +3966,15 @@ If current buffer is in `inferior-python-mode', return it."
 
 (defun python-shell-get-process ()
   "Return inferior Python process for current buffer."
-  (get-buffer-process (python-shell-get-buffer)))
+  (unless (and python-shell--process-cache-valid
+               (or (not python-shell--process-cache)
+                   (and (process-live-p python-shell--process-cache)
+                        (buffer-live-p
+                         (process-buffer python-shell--process-cache)))))
+    (setq python-shell--process-cache
+          (get-buffer-process (python-shell-get-buffer))
+          python-shell--process-cache-valid t))
+  python-shell--process-cache)
 
 (defun python-shell-get-process-or-error (&optional interactivep)
   "Return inferior Python process for current buffer or signal error.