fix: when run from web with -f a_file_folder/ caused page title is None as locustfile argument is None

[alterhu2020]

Steps:

1. run the locust with command -f a_file_folder/ the locustfile argument is a folder, so in the main.py it will return locustfile as None
2. When start the test, then the web page title Locust for None shows, we need to correct the locustfile variable at this situation

[cyberw]

Wouldnt this cause issues on repeated runs? I mean wouldnt the second run show the same users as the first even if the user had changed the selection?

[alterhu2020]

Wouldnt this cause issues on repeated runs? I mean wouldnt the second run show the same users as the first even if the user had changed the selection?

Hi @cyberw the above code can show the changed user when we switch to another selected user. But here comes another issue, we need to refresh the page to make the changes take affect.
So we need to change the locustfile variable in this function: locust.web.WebUI.update_template_args as well.

please take consider this issue should we change the code in above location as well ? thanks

[cyberw]

I dont have many opinions on the UI, and never use it myself :) So whatever works and doesnt show incorrect info…

[cyberw]

Need to fix the code formatting though...

[cyberw]

@alterhu2020 This is probably a good fix, you just need to run Black to format your code..