debugshell: disable demand importer when importing debugger
For reasons I can't explain (but likely have something to do with a
combination of __import__ inferring default values for arguments and
the demand importer mechanism further assuming defaults), the demand
importer isn't playing well with IPython. Without this patch, we get
a failure "ValueError: Attempted relative import in non-package" when
attempting to import "IPython." The stack has numerous demandimport
calls on it and adding "IPython" to the exclude list in demandimport
isn't enough to make the problem go away, which means the issue is
likely somewhere in the bowells of IPython. It's easier to just disable
the demand importer when importing the debugger.
#!/usr/bin/env python
#
# check-py3-compat - check Python 3 compatibility of Mercurial files
#
# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import, print_function
import ast
import sys
def check_compat(f):
"""Check Python 3 compatibility for a file."""
with open(f, 'rb') as fh:
content = fh.read()
# Ignore empty files.
if not content.strip():
return
root = ast.parse(content)
futures = set()
haveprint = False
for node in ast.walk(root):
if isinstance(node, ast.ImportFrom):
if node.module == '__future__':
futures |= set(n.name for n in node.names)
elif isinstance(node, ast.Print):
haveprint = True
if 'absolute_import' not in futures:
print('%s not using absolute_import' % f)
if haveprint and 'print_function' not in futures:
print('%s requires print_function' % f)
if __name__ == '__main__':
for f in sys.argv[1:]:
check_compat(f)
sys.exit(0)