Refactor fence block code to never infinite loop

(imported from commit f72cb182e4fc9c4e8003853276d8aa40b454d08f)

zephyr/lib/bugdown/fenced_code.py

@@ -95,36 +95,8 @@ class FencedBlockPreprocessor(markdown.preprocessors.Preprocessor):
         self.checked_for_codehilite = False
         self.codehilite_conf = {}
 
-    def run(self, lines):
-        """ Match and store Fenced Code Blocks in the HtmlStash. """
-
-        # Check for code hilite extension
-        if not self.checked_for_codehilite:
-            for ext in self.markdown.registeredExtensions:
-                if isinstance(ext, CodeHiliteExtension):
-                    self.codehilite_conf = ext.config
-                    break
-
-            self.checked_for_codehilite = True
-
-        text = "\n".join(lines)
-        while 1:
-            m = FENCED_BLOCK_RE.search(text)
-            if not m:
-                fence = FENCE_RE.search(text)
-                if fence:
-                    # If we found a starting fence but no ending fence,
-                    # then we add a closing fence before the two newlines that
-                    # markdown automatically inserts
-                    if text[-2:] == '\n\n':
-                        text = text[:-2] + '\n' + fence.group('fence') + text[-2:]
-                    else:
-                        text += fence.group('fence')
-
-                    continue
-                else:
-                    break
 
+    def process_fence(self, m, text):
         lang = ''
         if m.group('lang'):
             lang = LANG_TAG % m.group('lang')
@@ -145,7 +117,44 @@ class FencedBlockPreprocessor(markdown.preprocessors.Preprocessor):
             code = CODE_WRAP % (lang, self._escape(m.group('code')))
 
         placeholder = self.markdown.htmlStash.store(code, safe=True)
-            text = '%s\n%s\n%s'% (text[:m.start()], placeholder, text[m.end():])
+        return '%s\n%s\n%s'% (text[:m.start()], placeholder, text[m.end():])
+
+    def run(self, lines):
+        """ Match and store Fenced Code Blocks in the HtmlStash. """
+
+        # Check for code hilite extension
+        if not self.checked_for_codehilite:
+            for ext in self.markdown.registeredExtensions:
+                if isinstance(ext, CodeHiliteExtension):
+                    self.codehilite_conf = ext.config
+                    break
+
+            self.checked_for_codehilite = True
+
+        text = "\n".join(lines)
+        end = 0
+        while 1:
+            m = FENCED_BLOCK_RE.search(text)
+            if m:
+                end = m.end()
+                text = self.process_fence(m, text)
+            else:
+                break
+
+
+        fence = FENCE_RE.search(text, end)
+        if fence:
+            # If we found a starting fence but no ending fence,
+            # then we add a closing fence before the two newlines that
+            # markdown automatically inserts
+            if text[-2:] == '\n\n':
+                text = text[:-2] + '\n' + fence.group('fence') + text[-2:]
+            else:
+                text += fence.group('fence')
+            m = FENCED_BLOCK_RE.search(text)
+            if m:
+                text = self.process_fence(m, text)
+
         return text.split("\n")
 
     def _escape(self, txt):