Class picker incorrectly populates Parsed Options

[Vino4]

Describe the bug

When using the Web UI's class picker, Parsed Options are incorrectly populated

Expected behavior

Each name of a picked class is available as a single item in the environment.parsed_options.user_classes list
Example when selecting the class "PurchaseUser":

Actual behavior

When choosing classes through class picker, the name of the class is broken into characters. Each character is present as its own item in the environment.parsed_options.user_classes list.
Example when selecting the class "PurchaseUser":

Steps to reproduce

• Start locust with the --class-picker option and without specifying a user class through the CLI
• Select a class from the class picker menu and start the test
• Access the environment.parsed_options.user_classes list in the test_start listener

@events.test_start.add_listener
def on_test_start(environment, **__):
    user_classes = environment.parsed_options.user_classes
    log.info(user_classes)

Environment

• OS: MacOS Big Sur (11.4)
• Python version: 3.7.9
• Locust version: 2.12.0
• Locust command line that you ran: locust --class-picker
• Locust file contents (anonymized if necessary):

import logging
import time
from locust import HttpUser, task, between, events

log = logging.getLogger(__name__)

@events.test_start.add_listener
def on_test_start(environment, **_):
    user_classes = environment.parsed_options.user_classes
    log.info(user_classes)

class PurchaseUser(HttpUser):
    wait_time = between(1, 5)

    @task
    def hello_world(self):
        self.client.get("/hello")
        self.client.get("/world")

    @task(3)
    def view_items(self):
        for item_id in range(10):
            self.client.get(f"/item?id={item_id}", name="/item")
            time.sleep(1)

    def on_start(self):
        self.client.post("/login", json={"username":"foo", "password":"bar"})

[cyberw]

@mikenester Could you take a look?

[mikenester]

Whoops! Yeah i'll take a look asap

[mikenester]

I think this is happening when /swarm updates environment.parsed_options. I'll try to get a fix in today or tomorrow

[mikenester]

@cyberw @Vino4 is the expected behavior on this issue correct?

If I have the following in a file called locustfiles/locustfile1.py

from locust import HttpUser, task, between, events


@events.test_start.add_listener
def on_test_start(environment, **__):
    user_classes = environment.parsed_options.user_classes
    print("\nevent listener:\n", user_classes)

class Base(HttpUser):
    wait_time = between(1, 2)

    @task
    def base(self):
        self.client.get("/")

It prints the following when Locust is ran with locust -f locustfiles --class-picker

event listener:
 ['B', 'a', 's', 'e']

Meanwhile, it prints the following when Locust is ran with locust -f locustfiles/locustfile1.py

event listener:
 []

Based on this, I would expect user_classes to be empty when a test is ran with the --class-picker flag.

[Vino4]

@cyberw @Vino4 is the expected behavior on this issue correct?

If I have the following in a file called locustfiles/locustfile1.py

from locust import HttpUser, task, between, events


@events.test_start.add_listener
def on_test_start(environment, **__):
    user_classes = environment.parsed_options.user_classes
    print("\nevent listener:\n", user_classes)

class Base(HttpUser):
    wait_time = between(1, 2)

    @task
    def base(self):
        self.client.get("/")

It prints the following when Locust is ran with locust -f locustfiles --class-picker

event listener:
 ['B', 'a', 's', 'e']

Meanwhile, it prints the following when Locust is ran with locust -f locustfiles/locustfile1.py

event listener:
 []

Based on this, I would expect user_classes to be empty when a test is ran with the --class-picker flag.

I'm very new to Locust so not quite sure, but from a users' perspective I propose that the expect behavior when running the following code snippet:

from locust import HttpUser, task, between, events


@events.init.add_listener
def on_init(environment, **__):
    user_classes = environment.parsed_options.user_classes
    print("\nInit event listener:\n", user_classes)

@events.test_start.add_listener
def on_test_start(environment, **__):
    user_classes = environment.parsed_options.user_classes
    print("\nTest start event listener:\n", user_classes)

class Base(HttpUser):
    wait_time = between(1, 2)

    @task
    def base(self):
        self.client.get("/")

with --class-picker and then starting the test is to produce the following output:

Init event listener:
 []

Test start event listener:
 ['Base']

The reasoning is: When I run locust -f locustfiles/locustfile1.py Base the output is:

Init event listener:
 ['Base']
[2022-09-11 17:34:13,697] MMBP.local/INFO/locust.main: Starting Locust 2.12.0

Test start event listener:
 ['Base']

This is operating under the assumption that the intended behavior when setting the class using class-picker is to simply specify the class when the test starts rather than when the test initializing :)

Support point: When specifying any custom arguments through the Web UI, they're injected into parsed_option when the test is started - a case could be made that --class-picker serves and function the same as a custom argument 😄

[mikenester]

@cyberw Any thoughts on the above ^ ?

[cyberw]

@Vino4 's comment makes sense to me.

[mikenester]

I have a PR open with the fix: #2201

[cyberw]

Should be fixed now