Add `narrow-format-all:python' to format narrowed Python buffers

README.org

@@ -2907,7 +2907,12 @@ mode independent [[https://github.com/joaotavora/eglot][eglot]] configuration:
    buffers for use with [[https://github.com/joaotavora/eglot][eglot]].  They are a refactored implementation of the post
    [[https://www.reddit.com/r/emacs/comments/w4f4u3/using_rustic_eglot_and_orgbabel_for_literate/][Using rustic, eglot, and org-babel with LSP support in Emacs]] for my use with
    Python.
-3. Listing [[lst:eglot-maybe-ensure]] starts [[https://github.com/joaotavora/eglot][eglot]] in case of proper programming
+3. Listing [[lst:narrow-format-all-python]] defines a function to format only the
+   narrowed region of Python =org-src-mode= blocks prepared by means of the code
+   in listing [[lst:setup-python-org-src-mode-for-eglot]]. *Do not use*
+ =format-all-buffer= *on such buffers*, since =format-all-buffer= does not
+   handle the narrowing.
+4. Listing [[lst:eglot-maybe-ensure]] starts [[https://github.com/joaotavora/eglot][eglot]] in case of proper programming
    modes and proper directory local variables (meaning in presence of a proper
    file [[info:emacs#Directory Variables][.dir-locals.el]] in the root directory of any project using proper
    programming modes).
@@ -2998,6 +3003,40 @@ mode independent [[https://github.com/joaotavora/eglot][eglot]] configuration:
     (advice-add 'org-edit-src-save :before #'undo-eglot-org-babel-edit-prep))
 #+end_src
 
+#+caption[Experimental =narrow-format-all:python=]:
+#+caption: Experimental =narrow-format-all:python=.
+#+name: lst:narrow-format-all-python
+#+begin_src emacs-lisp
+  (when (and (fboundp 'eglot-ensure)
+             (fboundp 'format-all-buffer))
+    (defun narrow-format-all:python ()
+      "Format narrowed Python `org-src-mode' buffers correctly.
+  Use this function instead of `format-all-buffer' on `org-babel-edit-prep:python'
+  prepared buffers."
+      (interactive)
+      (when (eq major-mode 'python-mode)
+        (let ((source-min (point-min))
+              (source-max (point-max))
+              (source (current-buffer))
+              (target (get-buffer-create "*narrow-format-all:python*")))
+          (with-current-buffer target
+            (barf-if-buffer-read-only)
+            (erase-buffer)
+            (save-excursion
+              (insert-buffer-substring-no-properties
+               source source-min source-max))
+            (python-mode)
+            (setq-local format-all-formatters '(("Python" black)))
+            (format-all-buffer)
+            (let ((target-min (point-min))
+                  (target-max (point-max)))
+              (with-current-buffer source
+                (erase-buffer)
+                (save-excursion
+                  (insert-buffer-substring-no-properties
+                   target target-min target-max)))))))))
+#+end_src
+
 #+caption[Start =eglot= in case of a proper =dir-local-variables-alist=]:
 #+caption: Start =eglot= in case of a proper =dir-local-variables-alist=.
 #+name: lst:eglot-maybe-ensure