remove ':' from field names

anki/models.py

@@ -338,6 +338,8 @@ and notes.mid = ? and cards.ord = ?""",
 
     def renameField(self, m: NoteType, field: Field, newName: Optional[str]) -> None:
         self.col.modSchema(check=True)
+        if newName is not None:
+            newName = newName.replace(":", "")
         pat = r"{{([^{}]*)([:#^/]|[^:#/^}][^:}]*?:|)%s}}"
 
         def wrap(txt):

aqt/clayout.py

@@ -49,6 +49,7 @@ class CardLayout(QDialog):
                 self.emptyFields.append(name)
                 note[name] = "(%s)" % name
             note.flush()
+        self.removeColons()
         self.setupTopArea()
         self.setupMainArea()
         self.setupButtons()
@@ -242,6 +243,12 @@ Please create a new card type first."""
             )
         self.redraw()
 
+    def removeColons(self):
+        # colons in field names conflict with the template language
+        for fld in self.model["flds"]:
+            if ":" in fld["name"]:
+                self.mm.renameField(self.model, fld, fld["name"])
+
     # Buttons
     ##########################################################################