Fixed #19677 -- Introspection of recursive foreign keys under SQLite.

Thanks Simon Charette.

django/db/backends/creation.py

@@ -77,7 +77,7 @@ class BaseDatabaseCreation(object):
                     field_output.append(tablespace_sql)
             if f.rel:
                 ref_output, pending = self.sql_for_inline_foreign_key_references(
-                    f, known_models, style)
+                    model, f, known_models, style)
                 if pending:
                     pending_references.setdefault(f.rel.to, []).append(
                         (model, f))
@@ -116,15 +116,16 @@ class BaseDatabaseCreation(object):
 
         return final_output, pending_references
 
-    def sql_for_inline_foreign_key_references(self, field, known_models, style):
+    def sql_for_inline_foreign_key_references(self, model, field, known_models, style):
         """
         Return the SQL snippet defining the foreign key reference for a field.
         """
         qn = self.connection.ops.quote_name
-        if field.rel.to in known_models:
+        rel_to = field.rel.to
+        if rel_to in known_models or rel_to == model:
             output = [style.SQL_KEYWORD('REFERENCES') + ' ' +
-                style.SQL_TABLE(qn(field.rel.to._meta.db_table)) + ' (' +
-                style.SQL_FIELD(qn(field.rel.to._meta.get_field(
+                style.SQL_TABLE(qn(rel_to._meta.db_table)) + ' (' +
+                style.SQL_FIELD(qn(rel_to._meta.get_field(
                     field.rel.field_name).column)) + ')' +
                 self.connection.ops.deferrable_sql()
             ]

django/db/backends/mysql/creation.py

@@ -38,7 +38,7 @@ class DatabaseCreation(BaseDatabaseCreation):
             suffix.append('COLLATE %s' % self.connection.settings_dict['TEST_COLLATION'])
         return ' '.join(suffix)
 
-    def sql_for_inline_foreign_key_references(self, field, known_models, style):
+    def sql_for_inline_foreign_key_references(self, model, field, known_models, style):
         "All inline references are pending under MySQL"
         return [], True
 

tests/regressiontests/introspection/models.py

@@ -23,6 +23,7 @@ class Article(models.Model):
     headline = models.CharField(max_length=100)
     pub_date = models.DateField()
     reporter = models.ForeignKey(Reporter)
+    response_to = models.ForeignKey('self', null=True)
 
     def __str__(self):
         return self.headline

tests/regressiontests/introspection/tests.py

@@ -106,13 +106,17 @@ class IntrospectionTests(TestCase):
         # should test that the response is correct.
         if relations:
             # That's {field_index: (field_index_other_table, other_table)}
-            self.assertEqual(relations, {3: (0, Reporter._meta.db_table)})
+            self.assertEqual(relations, {3: (0, Reporter._meta.db_table),
+                                         4: (0, Article._meta.db_table)})
 
     @skipUnlessDBFeature('can_introspect_foreign_keys')
     def test_get_key_columns(self):
         cursor = connection.cursor()
         key_columns = connection.introspection.get_key_columns(cursor, Article._meta.db_table)
-        self.assertEqual(key_columns, [('reporter_id', Reporter._meta.db_table, 'id')])
+        self.assertEqual(
+            set(key_columns),
+            set([('reporter_id', Reporter._meta.db_table, 'id'),
+                 ('response_to_id', Article._meta.db_table, 'id')]))
 
     def test_get_primary_key_column(self):
         cursor = connection.cursor()