add as_mql() fallback for generating annotations

as_mql_agg() only needs to be defined if it differs from as_mql()

Author: timgraham

django_mongodb/functions.py

@@ -54,8 +54,8 @@ def round_(self, compiler, connection):
 
 
 def register_functions():
-    Cot.as_mql_agg = cot
+    Cot.as_mql = cot
     Extract.as_mql = extract
-    Func.as_mql_agg = func
-    Log.as_mql_agg = log
-    Round.as_mql_agg = round_
+    Func.as_mql = func
+    Log.as_mql = log
+    Round.as_mql = round_

django_mongodb/query.py

@@ -91,7 +91,8 @@ def get_cursor(self):
                 column = expr.target.column
             except AttributeError:
                 # Generate the MQL for an annotation.
-                fields[name] = expr.as_mql_agg(self.compiler, self.connection)
+                method = 'as_mql_agg' if hasattr(expr, 'as_mql_agg') else 'as_mql'
+                fields[name] = getattr(expr, method)(self.compiler, self.connection)
             else:
                 # If name != column, then this is an annotatation referencing
                 # another column.