Better treatment of line length limits for the Python inferior

* lisp/comint.el (comint-max-line-length): New constant reflecting a
safe maximum line size that can be sent to an inferior process.
* lisp/progmodes/python.el
(python-shell-comint-watch-for-first-prompt-output-filter): Send setup
code to the inferior process only once and at this stage.
(python-shell-eval-setup-code, python-shell-eval-file-setup-code):
Move, unchanged, to an earlier point to avoid byte-compiler warnings.
(python-shell-send-string-no-output): Revert changes of e32c7d2a8d
(python-shell-send-string): Use 'comint-max-line-length' to decide
when to resort to temp files.
(python-shell-send-string, python-shell-send-file): Don't send setup
code each time (bug#49822).

1 files changed, 51 insertions, 47 deletions

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index db7008df244..8f7bb7a8b60 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -2811,6 +2811,44 @@ eventually provide a shell."
   :type 'hook
   :group 'python)
 
+(defconst python-shell-eval-setup-code
+  "\
+def __PYTHON_EL_eval(source, filename):
+    import ast, sys
+    if sys.version_info[0] == 2:
+        from __builtin__ import compile, eval, globals
+    else:
+        from builtins import compile, eval, globals
+    sys.stdout.write('\\n')
+    try:
+        p, e = ast.parse(source, filename), None
+    except SyntaxError:
+        t, v, tb = sys.exc_info()
+        sys.excepthook(t, v, tb.tb_next)
+        return
+    if p.body and isinstance(p.body[-1], ast.Expr):
+        e = p.body.pop()
+    try:
+        g = globals()
+        exec(compile(p, filename, 'exec'), g, g)
+        if e:
+            return eval(compile(ast.Expression(e.value), filename, 'eval'), g, g)
+    except Exception:
+        t, v, tb = sys.exc_info()
+        sys.excepthook(t, v, tb.tb_next)"
+  "Code used to evaluate statements in inferior Python processes.")
+
+(defconst python-shell-eval-file-setup-code
+  "\
+def __PYTHON_EL_eval_file(filename, tempname, encoding, delete):
+    import codecs, os
+    with codecs.open(tempname or filename, encoding=encoding) as file:
+        source = file.read().encode(encoding)
+    if delete and tempname:
+        os.remove(tempname)
+    return __PYTHON_EL_eval(source, filename)"
+  "Code used to evaluate files in inferior 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)
@@ -2826,6 +2864,15 @@ eventually provide a shell."
           (setq python-shell--first-prompt-received-output-buffer nil)
         (setq-local python-shell--first-prompt-received t)
         (setq python-shell--first-prompt-received-output-buffer nil)
+        (cl-letf (((symbol-function 'python-shell-send-string)
+                   (lambda (string process)
+                     (comint-send-string
+                      process
+                      (format "exec(%s)\n" (python-shell--encode-string string))))))
+          ;; Bootstrap: the normal definition of `python-shell-send-string'
+          ;; depends on the Python code sent here.
+          (python-shell-send-string-no-output python-shell-eval-setup-code)
+          (python-shell-send-string-no-output python-shell-eval-file-setup-code))
         (with-current-buffer (current-buffer)
           (let ((inhibit-quit nil))
             (run-hooks 'python-shell-first-prompt-hook))))))
@@ -3081,33 +3128,6 @@ there for compatibility with CEDET.")
       (delete-trailing-whitespace))
     temp-file-name))
 
-(defconst python-shell-eval-setup-code
-  "\
-def __PYTHON_EL_eval(source, filename):
-    import ast, sys
-    if sys.version_info[0] == 2:
-        from __builtin__ import compile, eval, globals
-    else:
-        from builtins import compile, eval, globals
-    sys.stdout.write('\\n')
-    try:
-        p, e = ast.parse(source, filename), None
-    except SyntaxError:
-        t, v, tb = sys.exc_info()
-        sys.excepthook(t, v, tb.tb_next)
-        return
-    if p.body and isinstance(p.body[-1], ast.Expr):
-        e = p.body.pop()
-    try:
-        g = globals()
-        exec(compile(p, filename, 'exec'), g, g)
-        if e:
-            return eval(compile(ast.Expression(e.value), filename, 'eval'), g, g)
-    except Exception:
-        t, v, tb = sys.exc_info()
-        sys.excepthook(t, v, tb.tb_next)"
-  "Code used to evaluate statements in inferior Python processes.")
-
 (defalias 'python-shell--encode-string
   (let ((fun (if (and (fboundp 'json-serialize)
                       (>= emacs-major-version 28))
@@ -3128,12 +3148,11 @@ t when called interactively."
   (interactive
    (list (read-string "Python command: ") nil t))
   (let ((process (or process (python-shell-get-process-or-error msg)))
-        (code (format "exec(%s);__PYTHON_EL_eval(%s, %s)\n"
-                      (python-shell--encode-string python-shell-eval-setup-code)
+        (code (format "__PYTHON_EL_eval(%s, %s)\n"
                       (python-shell--encode-string string)
                       (python-shell--encode-string (or (buffer-file-name)
                                                        "<string>")))))
-    (if (<= (string-bytes code) 4096)
+    (if (<= (string-bytes code) comint-max-line-length)
         (comint-send-string process code)
       (let* ((temp-file-name (with-current-buffer (process-buffer process)
                                (python-shell--save-temp-file string)))
@@ -3180,8 +3199,7 @@ Return the output."
         (inhibit-quit t))
     (or
      (with-local-quit
-       (comint-send-string
-        process (format "exec(%s)\n" (python-shell--encode-string string)))
+       (python-shell-send-string string process)
        (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
@@ -3378,18 +3396,6 @@ t when called interactively."
        nil ;; noop
        msg))))
 
-
-(defconst python-shell-eval-file-setup-code
-  "\
-def __PYTHON_EL_eval_file(filename, tempname, encoding, delete):
-    import codecs, os
-    with codecs.open(tempname or filename, encoding=encoding) as file:
-        source = file.read().encode(encoding)
-    if delete and tempname:
-        os.remove(tempname)
-    return __PYTHON_EL_eval(source, filename)"
-  "Code used to evaluate files in inferior Python processes.")
-
 (defun python-shell-send-file (file-name &optional process temp-file-name
                                          delete msg)
   "Send FILE-NAME to inferior Python PROCESS.
@@ -3419,9 +3425,7 @@ t when called interactively."
     (comint-send-string
      process
      (format
-      "exec(%s);exec(%s);__PYTHON_EL_eval_file(%s, %s, %s, %s)\n"
-      (python-shell--encode-string python-shell-eval-setup-code)
-      (python-shell--encode-string python-shell-eval-file-setup-code)
+      "__PYTHON_EL_eval_file(%s, %s, %s, %s)\n"
       (python-shell--encode-string file-name)
       (python-shell--encode-string (or temp-file-name ""))
       (python-shell--encode-string (symbol-name encoding))