Cannot Update Custom options in the Web UI when Default Value is None

[timhovius]

Prerequisites

• I am using the latest version of Locust
• I am reporting a bug, not asking a question

Description

When custom options are set through the Locust WebUI, they consistently return None when accessed via self.environment.parsed_options. In this case, when running lucust -f tasks.py --username test the username is test. That's correct, but when I set this option through the Locust WebUI, it is None which is incorrect.

Command line

lucust -f tasks.py

Locustfile contents

@events.init_command_line_parser.add_listener
def _(parser: LocustArgumentParser):
    parser.add_argument('--user', '--username', dest='username', default=None, help='username')

Python version

3.10

Locust version

2.32.4

Operating system

Linux