Non Empty String

A simple wrapper type for Strings that ensures that the string inside is not .empty(), meaning that the length > 0.

Example

use non_empty_string::NonEmptyString;

// Constructing it from a normal (non-zero-length) String works fine.
let s = "A string with a length".to_owned();
assert!(NonEmptyString::new(s).is_ok());

// But constructing it from a zero-length String results in an `Err`, where we get the `String` back that we passed in.
let empty = "".to_owned();
let result = NonEmptyString::new(empty);
assert!(result.is_err());
assert_eq!(result.unwrap_err(), "".to_owned())

Methods of std::string::String

NonEmptyString implements a subset of the functions of std::string::String, only the ones which are guaranteed to leave the NonEmptyString in a valid state. This means i.e. push() is implemented, but pop() is not.

This allows you to mostly treat it as a String without having to constantly turn it into the inner String before you can do any sort of operation on it and then having to reconstruct a NonEmptyString afterwards.

If a method is missing that you think upholds the invariant of NonEmptyString, don't hesitate to open an issue.

Traits

NonEmptyString implements quite a few of the traits that String implements, where it simply forwards it to the underlying string, which allows e.g. indexing with ranges:

use non_empty_string::NonEmptyString;

let non_empty = NonEmptyString::new("ABC".to_owned()).unwrap();
assert_eq!(&non_empty[1..], "BC");

If a trait is missing that you think upholds the invariant of NonEmptyString, don't hesitate to open an issue.

Serde Support

serde support is available behind the serde feature flag:

[dependencies]
serde = { version = "1", features = ["derive"] }
non-empty-string = { version = "*", features = ["serde"]}

Afterwards you can use it in a struct:

use serde::{Serialize, Deserialize};
use non_empty_string::NonEmptyString;

#[derive(Serialize, Deserialize)]
struct MyApiObject {
  username: NonEmptyString,
}

Deserialization will fail if the field is present as a String, but the length of the String is 0.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.