add the flaskext_compat module

This is needed because changed the paths of flask extensions.
flaskext_compat makes sure they can be imported both the old and new
way.

2 files changed, 129 insertions, 0 deletions

diff --git a/app.py b/app.py
index c43f0be..46e3729 100644
--- a/app.py
+++ b/app.py
@@ -1,4 +1,8 @@
 # -*- coding: utf-8 -*-
+
+import flaskext_compat
+flaskext_compat.activate()
+
 import os
 from flask import Flask, request, redirect, url_for, flash, session
 from utils import templated, login_required, encrypt_password, decrypt_password, login_user, logout_user
diff --git a/flaskext_compat.py b/flaskext_compat.py
new file mode 100644
index 0000000..cb0b436
--- /dev/null
+++ b/flaskext_compat.py
@@ -0,0 +1,125 @@
+# -*- coding: utf-8 -*-
+"""
+    flaskext_compat
+    ~~~~~~~~~~~~~~~
+
+    Implements the ``flask.ext`` virtual package for versions of Flask
+    older than 0.7.  This module is a noop if Flask 0.8 was detected.
+
+    Usage::
+
+        import flaskext_compat
+        flaskext_compat.activate()
+        from flask.ext import foo
+
+    :copyright: (c) 2011 by Armin Ronacher.
+    :license: BSD, see LICENSE for more details.
+"""
+import sys
+import os
+import imp
+
+
+class ExtensionImporter(object):
+    """This importer redirects imports from this submodule to other locations.
+    This makes it possible to transition from the old flaskext.name to the
+    newer flask_name without people having a hard time.
+    """
+
+    def __init__(self, module_choices, wrapper_module):
+        self.module_choices = module_choices
+        self.wrapper_module = wrapper_module
+        self.prefix = wrapper_module + '.'
+        self.prefix_cutoff = wrapper_module.count('.') + 1
+
+    def __eq__(self, other):
+        return self.__class__.__module__ == other.__class__.__module__ and \
+               self.__class__.__name__ == other.__class__.__name__ and \
+               self.wrapper_module == other.wrapper_module and \
+               self.module_choices == other.module_choices
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def install(self):
+        sys.meta_path[:] = [x for x in sys.meta_path if self != x] + [self]
+
+    def find_module(self, fullname, path=None):
+        if fullname.startswith(self.prefix):
+            return self
+
+    def load_module(self, fullname):
+        if fullname in sys.modules:
+            return sys.modules[fullname]
+        modname = fullname.split('.', self.prefix_cutoff)[self.prefix_cutoff]
+        for path in self.module_choices:
+            realname = path % modname
+            try:
+                __import__(realname)
+            except ImportError:
+                exc_type, exc_value, tb = sys.exc_info()
+                # since we only establish the entry in sys.modules at the
+                # end this seems to be redundant, but if recursive imports
+                # happen we will call into the move import a second time.
+                # On the second invocation we still don't have an entry for
+                # fullname in sys.modules, but we will end up with the same
+                # fake module name and that import will succeed since this
+                # one already has a temporary entry in the modules dict.
+                # Since this one "succeeded" temporarily that second
+                # invocation now will have created a fullname entry in
+                # sys.modules which we have to kill.
+                sys.modules.pop(fullname, None)
+
+                # If it's an important traceback we reraise it, otherwise
+                # we swallow it and try the next choice.  The skipped frame
+                # is the one from __import__ above which we don't care about.
+                if self.is_important_traceback(realname, tb):
+                    raise exc_type, exc_value, tb.tb_next
+                continue
+            module = sys.modules[fullname] = sys.modules[realname]
+            if '.' not in modname:
+                setattr(sys.modules[self.wrapper_module], modname, module)
+            return module
+        raise ImportError('No module named %s' % fullname)
+
+    def is_important_traceback(self, important_module, tb):
+        """Walks a traceback's frames and checks if any of the frames
+        originated in the given important module.  If that is the case then we
+        were able to import the module itself but apparently something went
+        wrong when the module was imported.  (Eg: import of an import failed).
+        """
+        while tb is not None:
+            if self.is_important_frame(important_module, tb):
+                return True
+            tb = tb.tb_next
+        return False
+
+    def is_important_frame(self, important_module, tb):
+        """Checks a single frame if it's important."""
+        g = tb.tb_frame.f_globals
+        if '__name__' not in g:
+            return False
+
+        module_name = g['__name__']
+
+        # Python 2.7 Behavior.  Modules are cleaned up late so the
+        # name shows up properly here.  Success!
+        if module_name == important_module:
+            return True
+
+        # Some python versions will clean up modules so early that the
+        # module name at that point is no longer set.  Try guessing from
+        # the filename then.
+        filename = os.path.abspath(tb.tb_frame.f_code.co_filename)
+        test_string = os.path.sep + important_module.replace('.', os.path.sep)
+        return test_string + '.py' in filename or \
+               test_string + os.path.sep + '__init__.py' in filename
+
+
+def activate():
+    import flask
+    ext_module = imp.new_module('flask.ext')
+    ext_module.__path__ = []
+    flask.ext = sys.modules['flask.ext'] = ext_module
+    importer = ExtensionImporter(['flask_%s', 'flaskext.%s'], 'flask.ext')
+    importer.install()