121 lines
5 KiB
Python
121 lines
5 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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flask.exthook
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~~~~~~~~~~~~~
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Redirect imports for extensions. This module basically makes it possible
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for us to transition from flaskext.foo to flask_foo without having to
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force all extensions to upgrade at the same time.
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When a user does ``from flask.ext.foo import bar`` it will attempt to
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import ``from flask_foo import bar`` first and when that fails it will
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try to import ``from flaskext.foo import bar``.
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We're switching from namespace packages because it was just too painful for
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everybody involved.
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This is used by `flask.ext`.
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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 os
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from ._compat import reraise
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class ExtensionImporter(object):
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"""This importer redirects imports from this submodule to other locations.
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This makes it possible to transition from the old flaskext.name to the
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newer flask_name without people having a hard time.
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"""
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def __init__(self, module_choices, wrapper_module):
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self.module_choices = module_choices
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self.wrapper_module = wrapper_module
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self.prefix = wrapper_module + '.'
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self.prefix_cutoff = wrapper_module.count('.') + 1
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def __eq__(self, other):
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return self.__class__.__module__ == other.__class__.__module__ and \
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self.__class__.__name__ == other.__class__.__name__ and \
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self.wrapper_module == other.wrapper_module and \
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self.module_choices == other.module_choices
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def __ne__(self, other):
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return not self.__eq__(other)
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def install(self):
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sys.meta_path[:] = [x for x in sys.meta_path if self != x] + [self]
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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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# since we only establish the entry in sys.modules at the
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# very this seems to be redundant, but if recursive imports
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# happen we will call into the move import a second time.
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# On the second invocation we still don't have an entry for
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# fullname in sys.modules, but we will end up with the same
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# fake module name and that import will succeed since this
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# one already has a temporary entry in the modules dict.
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# Since this one "succeeded" temporarily that second
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# invocation now will have created a fullname entry in
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# sys.modules which we have to kill.
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sys.modules.pop(fullname, None)
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# If it's an important traceback we reraise it, otherwise
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# we swallow it and try the next choice. The skipped frame
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# is the one from __import__ above which we don't care about
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if self.is_important_traceback(realname, tb):
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reraise(exc_type, exc_value, tb.tb_next)
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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(sys.modules[self.wrapper_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 then we
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were able to import the module itself but apparently something went
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wrong when the module was imported. (Eg: import of an import failed).
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"""
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while tb is not None:
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if self.is_important_frame(important_module, tb):
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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 is_important_frame(self, important_module, tb):
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"""Checks a single frame if it's important."""
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g = tb.tb_frame.f_globals
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if '__name__' not in g:
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return False
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module_name = g['__name__']
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# Python 2.7 Behavior. Modules are cleaned up late so the
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# name shows up properly here. Success!
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if module_name == important_module:
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return True
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# Some python versions will will clean up modules so early that the
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# module name at that point is no longer set. Try guessing from
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# the filename then.
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filename = os.path.abspath(tb.tb_frame.f_code.co_filename)
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test_string = os.path.sep + important_module.replace('.', os.path.sep)
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return test_string + '.py' in filename or \
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test_string + os.path.sep + '__init__.py' in filename
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