Add Uri.empty constant representing an empty URI, equivalent to ""

[diemogebhardt]

This PR is regarding issues #619 and #618. More specifically: #619 (comment).

It introduces a Uri.empty constant, useful as a starting point for constructing URIs with minimal boilerplate.

Examples

let empty_uri = Uri.empty

// -> Uri(
//   scheme: None,
//   userinfo: None,
//   host: None,
//   port: None,
//   path: "",
//   query: None,
//   fragment: None,
// )

// Create a URI by overriding only the needed fields:

let localhost_uri = Uri(..Uri.empty, scheme: Some("http"), host: Some("localhost"))

// -> Uri(
//   scheme: Some("http"),
//   userinfo: None,
//   host: Some("localhost"),
//   port: None,
//   path: "",
//   query: None,
//   fragment: None,
// )

[lpil]

Is new the right name here? What does an empty URI mean?

[diemogebhardt]

Is new the right name here? What does an empty URI mean?

As string, this constant represents "". What is the proper term when picturing a "" string, <a href="">, a URI/URL form field or a browser address bar without any content?

Uri.empty or Uri.blank make sense to me as a non-native speaker. The Android API has the concept of an empty URI: https://developer.android.com/reference/android/net/Uri#EMPTY

Uri.default? It's not a URI containing default values.

Uri.new? We are not really constructing anything. But as a concept it is known and might make sense. Would you prefer it to be implemented as a Uri.new() function?

[lpil]

Great, that's very helpful thank you. Let's add that 'equivalent to ""', like in the Android docs there, I think that is a lot clearer.

Could you remove one of the two examples please, it's quite verbose showing the same thing twice, and the HTML documentation and the link to the code already show the structure.

[diemogebhardt]

Ok, done! :)

Updated one example to use the Uri.empty.

And changed two examples to use secure https://example.com instead of insecure http://example.com. They are just examples, yet it doesn't hurt to show best practices.

[lpil]

Thank you!