bug#56635: 29.0.50; [PATCH] hide-show in python-mode supports ONLY function and class blocks

[kobarity <kobarity@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 2336 bytes --]

I wrote:
> This code solves many problems of `hs-hide-block' mentioned in the
> first mail, but it breaks `hs-hide-level'.  It seems that current
> MDATA-SELECTOR support is limited and needs some fixes if we want to
> do something like above.  I will look into this a little bit more.

There are some problems in this approach.  The biggest one is the way
of processing in `hs-hide-level-recursive'.  It basically repeats:

1. hs-hide-block-at-point
2. forward-comment
3. re-search-forward hs-block-start-regexp

Let me explain with the following code:

#+begin_src python
class C:
    def a():
        pass

    def b():
        pass
#+end_src

Let's assume that point is at the beginning of the line "def a():".
The first step hides the method "a" and moves the point to the end of the
block.  The second step moves the point to the position "d" of "def b():",
not the beginning of the line.  Therefore, if hs-block-start-regexp
contains rx line-start, it fails to match "def b():".

Although this can be solved by adding a flag or a mode specific
forward-comment function to hs-special-modes-alist, I'm not sure if it
is the right approach.

So I think the following setting is best at this moment.

#+begin_src elisp
  (add-to-list
   'hs-special-modes-alist
   `(python-mode
     ,(python-rx (seq (* (syntax ?-)) block-start))
     ;; Use the empty string as end regexp so it doesn't default to
     ;; "\\s)".  This way parens at end of defun are properly hidden.
     ""
     "#"
     python-hideshow-forward-sexp-function
     nil))
#+end_src

(* (syntax ?-)) corresponds to "\\s-*" of the current regexp.  It
allows the point to be located before the block start symbols.

Another idea to improve the behavior of hiding a block is to provide a
wrapper function of `hs-hide-block' as follows and remap the key
bindings to this function like `python-mark-defun'.  With this
approach, C-c @ C-d and C-c @ C-h work as expected with the example
shown in the first mail.

#+begin_src elisp
(defun python-hideshow-hide-block (&optional end)
  "Python specific `hs-hide-block' function for `hs-minor-mode'.
Argument END is passed to `hs-hide-block'."
  (interactive "P")
  (python-nav-beginning-of-block)
  (hs-hide-block end))
#+end_src

Attached is a PoC level patch of this approach.  What do you think of
this approach?

Regards,

[-- Attachment #2: 56635-poc.patch --]
[-- Type: application/octet-stream, Size: 2082 bytes --]

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index b8fc7d4c54..ca8bff9a6e 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -303,6 +303,8 @@ python-mode-map
     (define-key map "\C-c\C-v" #'python-check)
     (define-key map "\C-c\C-f" #'python-eldoc-at-point)
     (define-key map "\C-c\C-d" #'python-describe-at-point)
+    ;; Hideshow
+    (define-key map [remap hs-hide-block] #'python-hideshow-hide-block)
     ;; Utilities
     (substitute-key-definition #'complete-symbol #'completion-at-point
                                map global-map)
@@ -4825,9 +4827,16 @@ python-describe-at-point
 (defun python-hideshow-forward-sexp-function (_arg)
   "Python specific `forward-sexp' function for `hs-minor-mode'.
 Argument ARG is ignored."
-  (python-nav-end-of-defun)
-  (unless (python-info-current-line-empty-p)
-    (backward-char)))
+  (python-nav-end-of-block))
+
+(declare-function hs-hide-block "hideshow")
+
+(defun python-hideshow-hide-block (&optional end)
+  "Python specific `hs-hide-block' function for `hs-minor-mode'.
+Argument END is passed to `hs-hide-block'."
+  (interactive "P")
+  (python-nav-beginning-of-block)
+  (hs-hide-block end))
 
 \f
 ;;; Imenu
@@ -5773,8 +5782,8 @@ python-mode
 
   (add-to-list
    'hs-special-modes-alist
-   '(python-mode
-     "\\s-*\\_<\\(?:def\\|class\\)\\_>"
+   `(python-mode
+     ,(python-rx (seq (* (syntax ?-)) block-start))
      ;; Use the empty string as end regexp so it doesn't default to
      ;; "\\s)".  This way parens at end of defun are properly hidden.
      ""
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 6f2ad87f81..bc56abaa2a 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -5857,8 +5857,11 @@ python-hideshow-hide-levels-1
 class SomeClass:
 
     def __init__(self, arg, kwarg=1):
+
     def filter(self, nums):
-    def __str__(self):"))))
+
+    def __str__(self):
+"))))
       (or enabled (hs-minor-mode -1)))))
 
 (ert-deftest python-hideshow-hide-levels-2 ()