properly generate clozed latex in unused media check (#775)

anki/media.py

@@ -108,8 +108,16 @@ If the same name exists, compare checksums."""
 
     def filesInStr(self, mid, string, includeRemote=False):
         l = []
-        # convert latex first
         model = self.col.models.get(mid)
+        strings = []
+        if model['type'] == MODEL_CLOZE and "{{c" in string:
+            # if the field has clozes in it, we'll need to expand the
+            # possibilities so we can render latex
+            strings = self._expandClozes(string)
+        else:
+            strings = [string]
+        for string in strings:
+            # handle latex
             string = mungeQA(string, None, None, model, None, self.col)
             # extract filenames
             for reg in self.regexps:
@@ -119,6 +127,24 @@ If the same name exists, compare checksums."""
                         l.append(fname)
         return l
 
+    def _expandClozes(self, string):
+        ords = set(re.findall("{{c(\d+)::.+?}}", string))
+        strings = []
+        from anki.template.template import clozeReg
+        def qrepl(m):
+            if m.group(3):
+                return "[%s]" % m.group(3)
+            else:
+                return "[...]"
+        def arepl(m):
+            return m.group(1)
+        for ord in ords:
+            s = re.sub(clozeReg%ord, qrepl, string)
+            s = re.sub(clozeReg%".+?", "\\1", s)
+            strings.append(s)
+        strings.append(re.sub(clozeReg%".+?", arepl, string))
+        return strings
+
     def transformNames(self, txt, func):
         for reg in self.regexps:
             txt = re.sub(reg, func, txt)