Refactored extension importing.

We now use importlib which means we no longer support Python 2.6.
Also, this refactor properly imports third party extensions which reside
at the root of PYTHONPATH. Previously, either `markdown.extensions.` or
`mdx_` would be appended to any extension name that did not contain a
dot, which required third party extensions to either be in submodules or
use the old `mdx_` naming convention.

This commit is also in preperation for #336. It will now be much easier to
deprecate (and later remove) support for the old ways of handling extension
names.

1 files changed, 17 insertions, 8 deletions

diff --git a/tests/test_apis.py b/tests/test_apis.py
index a5e0d73..f0c7f3d 100644
--- a/tests/test_apis.py
+++ b/tests/test_apis.py
@@ -276,24 +276,33 @@ class TestErrors(unittest.TestCase):
 
     def testLoadBadExtension(self):
         """ Test loading of an Extension with no makeExtension function. """
-        _create_fake_extension(name='fake', has_factory_func=False)
-        self.assertRaises(AttributeError, markdown.Markdown, extensions=['fake'])
+        _create_fake_extension(name='fake_a', has_factory_func=False)
+        self.assertRaises(AttributeError, markdown.Markdown, extensions=['fake_a'])
 
     def testNonExtension(self):
         """ Test loading a non Extension object as an extension. """
-        _create_fake_extension(name='fake', is_wrong_type=True)
-        self.assertRaises(TypeError, markdown.Markdown, extensions=['fake'])
+        _create_fake_extension(name='fake_b', is_wrong_type=True)
+        self.assertRaises(TypeError, markdown.Markdown, extensions=['fake_b'])
 
     def testBaseExtention(self):
         """ Test that the base Extension class will raise NotImplemented. """
-        _create_fake_extension(name='fake')
+        _create_fake_extension(name='fake_c')
         self.assertRaises(NotImplementedError, 
-                        markdown.Markdown, extensions=['fake'])
+                        markdown.Markdown, extensions=['fake_c'])
+
+    def testDotSyntaxExtention(self):
+        """ Test that dot syntax imports properly (not using mdx_). """
+        _create_fake_extension(name='fake_d', use_old_style=False)
+        self.assertRaises(NotImplementedError, 
+                        markdown.Markdown, extensions=['fake_d'])
 
 
-def _create_fake_extension(name, has_factory_func=True, is_wrong_type=False):
+def _create_fake_extension(name, has_factory_func=True, is_wrong_type=False, use_old_style=True):
     """ Create a fake extension module for testing. """
-    mod_name = '_'.join(['mdx', name])
+    if use_old_style:
+        mod_name = '_'.join(['mdx', name])
+    else:
+        mod_name = name
     if not PY3:
         # mod_name must be bytes in Python 2.x
         mod_name = bytes(mod_name)