bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

[Ola Nilsson]

The infinite recursion is triggered when the first line of a
python-mode buffer starts with space and ends with a backslash.

With emacs -Q

* create a new buffer
* M-x python-mode
* Insert SPACE \ ENTER

=> Lisp nesting exceeds ‘max-lisp-eval-depth’

The infinite recursion is also triggered if the first line of a narrowed
region starts with space and ends on a backslash.


I ran into this problem using mmm-mode with python submode regions.
The file format (bitbake from the Yocto Project) uses this style of
python function:

python foo() {
    # Python code here
    ...
}

mmm-mode narrows to the function content for fontification and if the
first line is properly indented Python code that ends with a backslash,
I see a list nesting error.

-- 
Ola

In GNU Emacs 26.0.91 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
 of 2018-01-23 built on blue
Repository revision: 1fc98ed073a2d26ad941748ecb13aa6f47dd7b01
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:    Debian GNU/Linux 9.3 (stretch)

Recent messages:
Desktop lazily opening font-lock.el.gz (2 remaining)...
uncompressing font-lock.el.gz...done
Desktop lazily opening font-lock.el.gz (2 remaining)...done
Desktop lazily opening mmm-mason.el (1 remaining)...done
Lazy desktop load complete
Sun Jan 28 19:48:27 2018: saving desktop file
Desktop saved in ~/.emacs.d/
Reverting buffer ‘useradd.bbclass’.
GNU Emacs 26.0.91 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
of 2018-01-23
Making completion list...

Configured using:
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bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

[Noam Postavsky]

found 30277 24.4
tag 30277 confirmed
quit

On Sun, Jan 28, 2018 at 5:42 PM, Ola Nilsson <ola.nilsson@gmail.com> wrote:
> The infinite recursion is triggered when the first line of a
> python-mode buffer starts with space and ends with a backslash.
>
> With emacs -Q
>
> * create a new buffer
> * M-x python-mode
> * Insert SPACE \ ENTER
>
> => Lisp nesting exceeds ‘max-lisp-eval-depth’
>
> The infinite recursion is also triggered if the first line of a narrowed
> region starts with space and ends on a backslash.

Happens back to 24.4, but not in 24.3.

bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

[Dmitry Gutov]

Hi!

On 1/29/18 1:42 AM, Ola Nilsson wrote:
> The infinite recursion is triggered when the first line of a
> python-mode buffer starts with space and ends with a backslash.
> 
> With emacs -Q
> 
> * create a new buffer
> * M-x python-mode
> * Insert SPACE \ ENTER
> 
> => Lisp nesting exceeds ‘max-lisp-eval-depth’
> 
> The infinite recursion is also triggered if the first line of a narrowed
> region starts with space and ends on a backslash.

This seems to fix it for me. Please test thoroughly, I rarely ever use 
python-mode myself.

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 5baf6e0f80..ff8269d970 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -1474,7 +1474,7 @@ python-nav-forward-defun
  (defun python-nav-beginning-of-statement ()
    "Move to start of current statement."
    (interactive "^")
-  (back-to-indentation)
+  (forward-line 0)
    (let* ((ppss (syntax-ppss))
           (context-point
            (or
@@ -1489,6 +1489,7 @@ python-nav-beginning-of-statement
               (python-info-line-ends-backslash-p))
             (forward-line -1)
             (python-nav-beginning-of-statement))))
+  (back-to-indentation)
    (point-marker))

  (defun python-nav-end-of-statement (&optional noend)

bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 1 Feb 2018 15:28:36 +0300
> 
> On 1/29/18 1:42 AM, Ola Nilsson wrote:
> > The infinite recursion is triggered when the first line of a
> > python-mode buffer starts with space and ends with a backslash.
> > 
> > With emacs -Q
> > 
> > * create a new buffer
> > * M-x python-mode
> > * Insert SPACE \ ENTER
> > 
> > => Lisp nesting exceeds ‘max-lisp-eval-depth’
> > 
> > The infinite recursion is also triggered if the first line of a narrowed
> > region starts with space and ends on a backslash.
> 
> This seems to fix it for me. Please test thoroughly, I rarely ever use 
> python-mode myself.

Please push to the master branch, and thanks.

bug#30277: 26.0.91; Infinite recursion in python-nav-beginning-of-statement

[Dmitry Gutov]

Version: 27.1

On 2/10/18 2:26 PM, Eli Zaretskii wrote:

> Please push to the master branch, and thanks.

OK, done.