allow empty clozes

instead of considering a cloze note with no clozes marked as invalid, treat it
as the first card and show a warning during review

anki/consts.py

@@ -46,6 +46,8 @@ SYNC_ZIP_SIZE = int(2.5*1024*1024)
 SYNC_URL = os.environ.get("SYNC_URL") or "https://beta.ankiweb.net/sync/"
 SYNC_VER = 5
 
+HELP_SITE="http://ankisrs.net/docs/dev/manual.html"
+
 # Labels
 ##########################################################################
 

anki/models.py

@@ -544,6 +544,9 @@ select id from notes where mid = ?)""" % " ".join(map),
                 "{{c(\d+)::[^}]*?}}", sflds[ord])])
         if -1 in ords:
             ords.remove(-1)
+        if not ords:
+            # empty clozes use first ord
+            return [0]
         return list(ords)
 
     # Sync handling

anki/template/template.py

@@ -4,6 +4,7 @@ import collections
 from anki.utils import stripHTML
 from anki.hooks import runFilter
 from anki.template import furigana; furigana.install()
+from anki.consts import HELP_SITE
 
 clozeReg = r"\{\{c%s::(.*?)(::(.*?))?\}\}"
 
@@ -196,8 +197,11 @@ class Template(object):
         reg = clozeReg
         m = re.search(reg%ord, txt)
         if not m:
-            # cloze doesn't exist; return empty
-            return ""
+            # cloze doesn't exist; return whole text
+            return (txt + "<p><font size=2>" + _(
+                "No cloze deletions found; showing whole field. (%s)") % (
+                    "<a href=%s#cloze>%s</a>" % (HELP_SITE, _("help"))) +
+                    "</font>")
         # replace chosen cloze with type
         if type == "q":
             if m.group(3):