Bug #120487 MySQLServerMock debug output prints an empty string due to use-after-move

• Submitted: 17 May 10:47
• Reporter: S F.
• Status: Open
• Category: MySQL Router
• Severity: S3 (Non-critical)
• Version: MySQL 9.6.0, commit 447eb26e094b444a88c5
• OS: Any
• CPU Architecture: Any
• Tags: mock-server, router

[17 May 10:47] S F.

Description:
MySQLServerMock::MySQLServerMock moves the expected_queries_file constructor parameter into expected_queries_file_ in the initializer list, then prints the moved-from parameter when debug_mode_ is enabled.

After the move, the parameter is valid but its value is unspecified. In practice it prints an empty filename:

```cpp
expected_queries_file_{std::move(expected_queries_file)},
// ...
std::cout << "\n\nExpected SQL queries come from file '"
          << expected_queries_file << "'\n\n"
          << std::flush;
```

How to repeat:
Compile a small program that constructs server_mock::MySQLServerMock with debug_mode=true and a non-empty expected_queries_file.

Observed output: Expected SQL queries come from file ''

Expected output should include the actual filename.

Suggested fix:
Print the member that owns the moved string:

```cpp
std::cout << "\n\nExpected SQL queries come from file '"
          << expected_queries_file_ << "'\n\n"
          << std::flush;
```