Select proper default for output_field based on distinct value

src/django_mysql/models/aggregates.py

@@ -1,4 +1,5 @@
 from django.db.models import Aggregate, CharField
+from django_mysql.models.fields import SetCharField, ListCharField
 
 
 class BitAnd(Aggregate):
@@ -24,8 +25,12 @@ def __init__(
     ):
 
         if "output_field" not in extra:
-            # This can/will be improved to SetTextField or ListTextField
-            extra["output_field"] = CharField()
+            if separator is not None:
+                extra["output_field"] = CharField()
+            elif distinct:
+                extra['output_field'] = SetCharField(CharField())
+            else:
+                extra['output_field'] = ListCharField(CharField())
 
         super().__init__(expression, **extra)
 

tests/testapp/test_aggregates.py

@@ -74,8 +74,7 @@ def setUp(self):
 
     def test_basic_aggregate_ids(self):
         out = self.shakes.tutees.aggregate(tids=GroupConcat("id"))
-        concatted_ids = ",".join(self.str_tutee_ids)
-        assert out == {"tids": concatted_ids}
+        assert out == {"tids": self.str_tutee_ids}
 
     def test_basic_annotate_ids(self):
         concat = GroupConcat("tutees__id")
@@ -104,14 +103,14 @@ def test_separator_big(self):
     def test_expression(self):
         concat = GroupConcat(F("id") + 1)
         out = self.shakes.tutees.aggregate(tids=concat)
-        concatted_ids = ",".join([str(self.jk.id + 1), str(self.grisham.id + 1)])
+        concatted_ids = [str(self.jk.id + 1), str(self.grisham.id + 1)]
         assert out == {"tids": concatted_ids}
 
     def test_application_order(self):
         out = Author.objects.exclude(id=self.shakes.id).aggregate(
             tids=GroupConcat("tutor_id", distinct=True)
         )
-        assert out == {"tids": str(self.shakes.id)}
+        assert out == {"tids": set(map(str,[self.shakes.id]))}
 
     @override_mysql_variables(SQL_MODE="ANSI")
     def test_separator_ansi_mode(self):
@@ -127,11 +126,11 @@ def test_ordering_invalid(self):
 
     def test_ordering_asc(self):
         out = self.shakes.tutees.aggregate(tids=GroupConcat("id", ordering="asc"))
-        assert out == {"tids": ",".join(self.str_tutee_ids)}
+        assert out == {"tids": self.str_tutee_ids}
 
     def test_ordering_desc(self):
         out = self.shakes.tutees.aggregate(tids=GroupConcat("id", ordering="desc"))
-        assert out == {"tids": ",".join(reversed(self.str_tutee_ids))}
+        assert out == {"tids": list(reversed(self.str_tutee_ids))}
 
     def test_separator_ordering(self):
         concat = GroupConcat("id", separator=":", ordering="asc")