Ignore empty dot command

Author: tanloong

Lib/sqlite3/__main__.py

@@ -59,8 +59,9 @@ def runsource(self, source, filename="<input>", symbol="single"):
                 case "quit":
                     sys.exit(0)
                 case _ as unknown:
-                    print("Error: unknown command or invalid arguments:  "
-                          f'"{unknown}". Enter ".help" for help')
+                    if unknown:
+                        print("Error: unknown command or invalid arguments:"
+                              f'  "{unknown}". Enter ".help" for help')
         else:
             if not sqlite3.complete_statement(source):
                 return True

Lib/test/test_sqlite3/test_cli.py

@@ -124,12 +124,15 @@ def test_interact_empty_source(self):
         self.assertEqual(out.count(self.PS2), 0)
 
     def test_interact_dot_commands_unknown(self):
-        out, err = self.run_cli(commands=(".unknown_command",))
+        out, err = self.run_cli(commands=(".unknown_command", "."))
         self.assertIn(self.MEMORY_DB_MSG, err)
         self.assertEndsWith(out, self.PS1)
-        self.assertEqual(out.count(self.PS1), 2)
+        self.assertEqual(out.count(self.PS1), 3)
         self.assertEqual(out.count(self.PS2), 0)
-        self.assertIn('Error: unknown command or invalid arguments:  "unknown_command"', out)
+        # test "unknown_command" is pointed out in the error message
+        self.assertIn("unknown_command", out)
+        # test ignore empty dot command "." to mimic sqlite3 CLI
+        self.assertEqual(out.count('Error'), 1)
 
     def test_interact_dot_commands_with_whitespaces(self):
         out, err = self.run_cli(commands=(".version ", ". version"))