Fixed #21126 -- QuerySet value conversion failure

A .annotate().select_related() query resulted in misaligned rows vs
columns for compiler.resolve_columns() method.

Report & patch by Michael Manfre.

django/db/backends/__init__.py

@@ -1167,7 +1167,7 @@ class BaseDatabaseOperations(object):
         Coerce the value returned by the database backend into a consistent type
         that is compatible with the field type.
         """
-        if value is None:
+        if value is None or field is None:
             return value
         internal_type = field.get_internal_type()
         if internal_type == 'FloatField':

django/db/models/sql/compiler.py

@@ -686,6 +686,10 @@ class SQLCompiler(object):
         has_aggregate_select = bool(self.query.aggregate_select)
         for rows in self.execute_sql(MULTI):
             for row in rows:
+                if has_aggregate_select:
+                    loaded_fields = self.query.get_loaded_field_names().get(self.query.model, set()) or self.query.select
+                    aggregate_start = len(self.query.extra_select) + len(loaded_fields)
+                    aggregate_end = aggregate_start + len(self.query.aggregate_select)
                 if resolve_columns:
                     if fields is None:
                         # We only set this up here because
@@ -712,12 +716,14 @@ class SQLCompiler(object):
                             db_table = self.query.get_meta().db_table
                             fields = [f for f in fields if db_table in only_load and
                                       f.column in only_load[db_table]]
+                        if has_aggregate_select:
+                            # pad None in to fields for aggregates
+                            fields = fields[:aggregate_start] + [
+                                None for x in range(0, aggregate_end - aggregate_start)
+                            ] + fields[aggregate_start:]
                     row = self.resolve_columns(row, fields)
 
                 if has_aggregate_select:
-                    loaded_fields = self.query.get_loaded_field_names().get(self.query.model, set()) or self.query.select
-                    aggregate_start = len(self.query.extra_select) + len(loaded_fields)
-                    aggregate_end = aggregate_start + len(self.query.aggregate_select)
                     row = tuple(row[:aggregate_start]) + tuple(
                         self.query.resolve_aggregate(value, aggregate, self.connection)
                         for (alias, aggregate), value

tests/aggregation_regress/tests.py

@@ -393,6 +393,17 @@ class AggregationTests(TestCase):
         qs = Entries.objects.annotate(clue_count=Count('clues__ID'))
         self.assertQuerysetEqual(qs, [])
 
+    def test_boolean_conversion(self):
+        # Aggregates mixed up ordering of columns for backend's convert_values
+        # method. Refs #21126.
+        e = Entries.objects.create(Entry='foo')
+        c = Clues.objects.create(EntryID=e, Clue='bar')
+        qs = Clues.objects.select_related('EntryID').annotate(Count('ID'))
+        self.assertQuerysetEqual(
+            qs, [c], lambda x: x)
+        self.assertEqual(qs[0].EntryID, e)
+        self.assertIs(qs[0].EntryID.Exclude, False)
+
     def test_empty(self):
         # Regression for #10089: Check handling of empty result sets with
         # aggregates