Update shape class' runner when Web UI picker is used

[wiatrak2]

a shape class' .runner member is set by _create_runner method of Environment class. However, when the UI picker is used, the shape_class member of an Environment instance is not initialized yet, hence, there's no Runner assignment on initialization. Therefore, if you'd like to refer to self.runner in your custom test shape (for instance to get the number of users running), you receive an error saying that self.runner is None.

Hence, I added the shape class runner initialization also when the shape class is selected with UI picker.

[cyberw]

Can you add a test case that fails without this change?

[wiatrak2]

There you go :)

[cyberw]

I see the need for the change, but update_shape_class_runner is a very weird method. Perhaps it can be refactored/renamed to something that makes more sense. Or just remove the method and have the "weird" behavior inline, where it is at least readable.

[wiatrak2]

I believe that we should avoid code repetition. Also I think that the action should be encapsulated by a method, as it wouldn't be clean to modify Environment's members from inside the WebUI. Thinking about a better name, my candidate is set_runner_in_shape_class - what do you think? 😅

[cyberw]

How about doing it here: https://github.com/locustio/locust/pull/2534/files#diff-498b8c363e788cc0210ac8600bce7660c60d210cad41af086886b79055c717beR636
, where we are already accessing the shape class directly.

Something like
shape_class.runner = self.environment.runner

environment-runner separation is very messy, and while I dont like duplication, I like methods with unclear meaning even less :)

[wiatrak2]

your code, your rules ;)

[cyberw]

Thx!