Replace homegrown OrderedDict with purpose-built Registry. (#688)

All processors and patterns now get "registered" to a Registry.
Each item is given a name (string) and a priority. The name is for
later reference and the priority can be either an integer or float
and is used to sort. Priority is sorted from highest to lowest. A 
Registry instance is a list-like iterable with the items auto-sorted 
by priority. If two items have the same priority, then they are 
listed in the order there were "registered". Registering a new 
item with the same name as an already registered item replaces
the old item with the new item (however, the new item is sorted by
its newly assigned priority). To remove an item, "deregister" it by 
name or index.

A backwards compatible shim is included so that existing simple
extensions should continue to work. DeprecationWarnings will 
be raised for any code which calls the old API.

Fixes #418.

1 files changed, 4 insertions, 5 deletions

diff --git a/markdown/postprocessors.py b/markdown/postprocessors.py
index f59e070..0fb4406 100644
--- a/markdown/postprocessors.py
+++ b/markdown/postprocessors.py
@@ -12,16 +12,15 @@ from __future__ import absolute_import
 from __future__ import unicode_literals
 from collections import OrderedDict
 from . import util
-from . import odict
 import re
 
 
 def build_postprocessors(md_instance, **kwargs):
     """ Build the default postprocessors for Markdown. """
-    postprocessors = odict.OrderedDict()
-    postprocessors["raw_html"] = RawHtmlPostprocessor(md_instance)
-    postprocessors["amp_substitute"] = AndSubstitutePostprocessor()
-    postprocessors["unescape"] = UnescapePostprocessor()
+    postprocessors = util.Registry()
+    postprocessors.register(RawHtmlPostprocessor(md_instance), 'raw_html', 30)
+    postprocessors.register(AndSubstitutePostprocessor(), 'amp_substitute', 20)
+    postprocessors.register(UnescapePostprocessor(), 'unescape', 10)
     return postprocessors