bug#21193: 25.0.50; python-shell-buffer-substring adds bogus if True: to unindented line

[Jorgen Schaefer]

Hello!

The function `python-shell-buffer-substring' can get confused when it is
used to send a substring of a line. It tries to add if True: around an
indented piece of code to prevent indentation errors, but it fails at
detecting indented code correctly:

(with-temp-buffer
  (insert "def foo():\n"
          "    print('a')\n")
  (re-search-backward "print")
  (python-shell-buffer-substring (point) (point-at-eol) t))

=>

"if True:
print('a')"

Note that the "print" line in the resulting code is not indented.

The expected result would be either "print('a')" or
"if True:\n    print('a')".

Regards,
Jorgen