bug#14352: 24.3; Python: narrow-to-defun narrows to class, not method

bug#14352: 24.3; Python: narrow-to-defun narrows to class, not method

[Eric Hanchrow]

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Please describe exactly what actions triggered the bug, and
the precise symptoms of the bug.  If you can, give a recipe
starting from `emacs -Q':

Put the following python program into a file named /tmp/repro.py.  It
should have 9 lines and 120 characters.

==>8====>8====>8====>8====>8====>8====>8====>8====>8====>8====>8====>8==
# Hello world

class Frotz(object):

    def meth(self):
        foo = 'bar'

    def seth(self):
        znort='frotz'
==8<====8<====8<====8<====8<====8<====8<====8<====8<====8<====8<====8<==

Start emacs with "emacs -Q".

C-x C-f /tmp/repro.py RET

M-x goto-line RET 5 RET

C-x n d

I see almost the entire file -- only the first two lines have been
hidden by narrowing.  I'd have expected to see only the two lines
starting with "def meth".

In GNU Emacs 24.3.1 (x86_64-apple-darwin, NS apple-appkit-1038.36)
 of 2013-03-12 on bob.porkrind.org
Windowing system distributor `Apple', version 10.3.1187
Configured using:
 `configure '--host=x86_64-apple-darwin' '--build=i686-apple-darwin'
 '--with-ns' 'build_alias=i686-apple-darwin'
 'host_alias=x86_64-apple-darwin' 'CC=gcc -mmacosx-version-min=10.7
 -isystem
 /Users/david/Xcode-10.7_4.5.2/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk/usr/include/
 -F/Users/david/Xcode-10.7_4.5.2/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk/System/Library/Frameworks''

Important settings:
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Python

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-x C-f / t m p / r e p <tab> <return> C-u C-n C-u
C-n C-n C-n C-n C-x n d M-x r e p o r t - e m <tab>
<return>

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emacs)

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bug#14352:

[Fabián Ezequiel Gallina]

Unfortunately, this seems like intended behavior (and I do agree that I
don't like it either). I suggest you raise this to emacs-devel if you
really want to change default behavior.

Check the `mark-defun' definition at
emacs/trunk/lisp/emacs-lisp/lisp.el:427 and you'll see that it does have
an explicit call to `beginning-of-defun' for "languages with nested
functions... e.g. Python."

A similar approach seems to takes place in `narrow-to-defun' at
emacs/trunk/lisp/emacs-lisp/lisp.el:470 which causes this.

From my side I've been narrowing defuns by calling `end-of-line' first
if I'm looking at it. You could rebind the `narrow-to-defun' command in
the `python-mode-map' to the following command:

    (defun python-narrow-to-defun (&optional _arg)
      "Make text outside current defun invisible.
    The defun visible is the one that contains point or follows
    point.  Optional ARG is ignored."
      (interactive)
      (save-excursion
        (end-of-line 1)
        (narrow-to-defun)))


Regards,
Fabián.