forked from orbit-oss/flask
9a70e62b8d
This implements a simple but elegant method to find out if an import error can be swallowed to try the next module or if the import error is important and must be reraised.
77 lines
2.4 KiB
Python
77 lines
2.4 KiB
Python
# -*- coding: utf-8 -*-
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"""
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flaskext_compat
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~~~~~~~~~~~~~~~
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Implements the ``flask.ext`` virtual package for versions of Flask
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older than 0.7. This module is a noop if Flask 0.8 was detected.
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Usage::
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import flaskext_compat
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from flask.ext import foo
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:copyright: (c) 2011 by Armin Ronacher.
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:license: BSD, see LICENSE for more details.
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"""
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import sys
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import imp
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ext_module = imp.new_module('flask.ext')
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ext_module.__path__ = []
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ext_module.__package__ = ext_module.__name__
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class _ExtensionImporter(object):
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"""This importer redirects imports from the flask.ext module to other
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locations.
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"""
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_module_choices = ['flask_%s', 'flaskext.%s']
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prefix = ext_module.__name__ + '.'
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prefix_cutoff = prefix.count('.')
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def find_module(self, fullname, path=None):
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if fullname.startswith(self.prefix):
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return self
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def load_module(self, fullname):
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if fullname in sys.modules:
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return sys.modules[fullname]
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modname = fullname.split('.', self.prefix_cutoff)[self.prefix_cutoff]
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for path in self._module_choices:
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realname = path % modname
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try:
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__import__(realname)
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except ImportError:
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exc_type, exc_value, tb = sys.exc_info()
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if self.is_important_traceback(realname, tb):
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raise exc_type, exc_value, tb
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continue
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module = sys.modules[fullname] = sys.modules[realname]
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if '.' not in modname:
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setattr(ext_module, modname, module)
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return module
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raise ImportError('No module named %s' % fullname)
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def is_important_traceback(self, important_module, tb):
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"""Walks a traceback's frames and checks if any of the frames
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originated in the given important module. If that is the case
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then we were able to import the module itself but apparently
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something went wrong when the module was imported. (Eg: import
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of an import failed).
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"""
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while tb is not None:
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if tb.tb_frame.f_globals.get('__name__') == important_module:
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return True
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tb = tb.tb_next
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return False
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def activate():
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"""Activates the compatibility system."""
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import flask
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if hasattr(flask, 'ext'):
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return
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sys.modules['flask.ext'] = flask.ext = ext_module
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sys.meta_path.append(_ExtensionImporter())
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