Bugfix: default Name implementation produces invalid URLs with empty packages.

[aaronjeline]

The default full_name() and type_url() implementations in the Name trait produce invalid type URLs when PACKAGE is empty.

Example:

#[derive(Clone, PartialEq, Debug, Default)]
struct Test {
    value: i32,
}

impl prost::Message for Test {
    // ... Message implementation ...
}

impl Name for Test {
    const PACKAGE: &'static str = "";
    const NAME: &'static str = "test";
    // Using default type_url()/full_name() implementation from Name trait
}

#[test]
fn empty_package_default_url_fails_roundtrip() {
  let type_url = Test::type_url();
  assert_eq!(type_url, "/.test"); // URL has leading dot
  TypeUrl::new(&type_url).unwrap(); // This panics
}

This will happen with any message type with PACKAGE = "" using the default type_url() implementation.

To fix, I adjusted the implementation of Name::full_name() to handle the special case of an empty package.

Let me know if you'd like me to adjust anything.

[jknovi]

LGTM! Thanks!

[GlenDC]

LGTM as well.