Fix unbound local error in GFM emphasis processing (#666)

CHANGES.md

@@ -6,6 +6,7 @@
 - [pull #640] Fix code friendly extra stopping other syntax being processed (#638)
 - [pull #644] Fix a number of em/strong issues (#641, #642, #643)
 - [pull #659] Fix a number of safemode issues (#647)
+- [pull #665] Rewrite emphasis and strong processing to be more GFM compliant
 
 
 ## python-markdown2 2.5.4

lib/markdown2.py

@@ -2786,17 +2786,19 @@ def has_middle(
         if len(open_syntax) < len(syntax) and opens:
             # expand the em span to the left, meaning we're covering additional chars.
             # check we don't cross an existing span border
-            if not self.body_crosses_span_borders(opens[-1], open):
-                middle = open
+            if self.body_crosses_span_borders(opens[-1], open):
+                return False
 
-                open = opens.pop(-1)
-                open_offset = unused_opens.pop(open, 0)
-                open_syntax = open.group(1)[open_offset:]
+            middle = open
 
-                if len(open_syntax) == len(syntax):
-                    # if it turns out the previous open is a perfect match then ignore the middle part
-                    # eg: **foo*bar**
-                    middle = None
+            open = opens.pop(-1)
+            open_offset = unused_opens.pop(open, 0)
+            open_syntax = open.group(1)[open_offset:]
+
+            if len(open_syntax) == len(syntax):
+                # if it turns out the previous open is a perfect match then ignore the middle part
+                # eg: **foo*bar**
+                middle = None
         elif len(open_syntax) > len(syntax) and unused_closes:
             # check if there is a previous closing delim run in the current body
             # since this is already within the body we don't need to do a cross-span border check

test/tm-cases/gfm_emphasis_issue666.html

@@ -0,0 +1 @@
+<p>*<a href="https://example.com/"><em>test</em>*</a></p>

test/tm-cases/gfm_emphasis_issue666.text

@@ -0,0 +1 @@
+*[*test**](https://example.com/)