Fixed #31615 -- Made migrations skip extension operations if not needed.

- Don't try to create an existing extension.
- Don't try to drop a nonexistent extension.

1 files changed, 28 insertions, 3 deletions

diff --git a/tests/postgres_tests/test_operations.py b/tests/postgres_tests/test_operations.py
index 0a9d8040ef..8cc9a2b66e 100644
--- a/tests/postgres_tests/test_operations.py
+++ b/tests/postgres_tests/test_operations.py
@@ -12,7 +12,8 @@ from . import PostgreSQLTestCase
 
 try:
     from django.contrib.postgres.operations import (
-        AddIndexConcurrently, CreateExtension, RemoveIndexConcurrently,
+        AddIndexConcurrently, BloomExtension, CreateExtension,
+        RemoveIndexConcurrently,
     )
     from django.contrib.postgres.indexes import BrinIndex, BTreeIndex
 except ImportError:
@@ -180,9 +181,33 @@ class CreateExtensionTests(PostgreSQLTestCase):
         with CaptureQueriesContext(connection) as captured_queries:
             with connection.schema_editor(atomic=False) as editor:
                 operation.database_forwards(self.app_label, editor, project_state, new_state)
-        self.assertIn('CREATE EXTENSION', captured_queries[0]['sql'])
+        self.assertEqual(len(captured_queries), 4)
+        self.assertIn('CREATE EXTENSION', captured_queries[1]['sql'])
         # Reversal.
         with CaptureQueriesContext(connection) as captured_queries:
             with connection.schema_editor(atomic=False) as editor:
                 operation.database_backwards(self.app_label, editor, new_state, project_state)
-        self.assertIn('DROP EXTENSION', captured_queries[0]['sql'])
+        self.assertEqual(len(captured_queries), 2)
+        self.assertIn('DROP EXTENSION', captured_queries[1]['sql'])
+
+    def test_create_existing_extension(self):
+        operation = BloomExtension()
+        project_state = ProjectState()
+        new_state = project_state.clone()
+        # Don't create an existing extension.
+        with CaptureQueriesContext(connection) as captured_queries:
+            with connection.schema_editor(atomic=False) as editor:
+                operation.database_forwards(self.app_label, editor, project_state, new_state)
+        self.assertEqual(len(captured_queries), 3)
+        self.assertIn('SELECT', captured_queries[0]['sql'])
+
+    def test_drop_nonexistent_extension(self):
+        operation = CreateExtension('tablefunc')
+        project_state = ProjectState()
+        new_state = project_state.clone()
+        # Don't drop a nonexistent extension.
+        with CaptureQueriesContext(connection) as captured_queries:
+            with connection.schema_editor(atomic=False) as editor:
+                operation.database_backwards(self.app_label, editor, project_state, new_state)
+        self.assertEqual(len(captured_queries), 1)
+        self.assertIn('SELECT', captured_queries[0]['sql'])