proposal: net/url: (*Userinfo).Username function should return bool value alongside with string

[otaxhu]

Proposal Details

I'm not an expert of the RFC documents for urls, I would like to know if the following urls are valid:

1. This is supposed to have a empty username and empty password (totally different from null username or password)

https://:@domain.com

2. This is supposed to have empty username and null password

https://@domain.com

3. This have both username and password null.

https://domain.com

If the second and third statements are true, then Userinfo functions Username and Password should have a mechanism in which should notify to the caller that this values are empty or null.

Password function already returns a bool value indicating presence or nullness of that field. I would like to know if it's correct to have Username function to return the same :)

[seankhliao]

The Username method signature cannot change, as it would break go1compat.
That said, UserInfo does already differentiate between itself being nil and the username being empty: https://go.dev/play/p/tOdeqGObADy