non

Type-safe wrappers for strings with compile-time guarantees.

Overview

non provides zero-cost wrapper types around String that encode specific invariants at the type level, preventing invalid states at runtime.

Wrappers guarantee things like non-empty strings, ASCII-only strings, exact length, and more — all enforced when creating the wrapper.

Features

• NonEmpty — ensures the string is not empty
• NonBlank — ensures the string contains at least one non-whitespace character
• ASCII — ensures the string contains only ASCII characters
• ExactLength<N> — ensures the string is exactly N characters long
• LowerCase — ensures the string is all lowercase
• UpperCase — ensures the string is all uppercase
• Trimmed — ensures no leading or trailing whitespace
• Alphanumeric — ensures string contains only alphanumeric characters

Supports composition of wrappers, e.g. ASCII<NonEmpty<String>>.

Works in no_std environments.

Usage

Add to your Cargo.toml:

[dependencies]
non = "0.1"

Basic usage:

use non::{NonEmpty, NonBlank, ASCII, ExactLength};

let valid = NonEmpty::new("hello".to_string()).unwrap();
assert!(NonEmpty::new("".to_string()).is_none());

let valid = NonBlank::new("hello".to_string()).unwrap();
assert!(NonBlank::new("   ".to_string()).is_none());

let valid = ASCII::new("hello".to_string()).unwrap();
assert!(ASCII::new("cześć".to_string()).is_none());

let valid = ExactLength::<2>::new("hi".to_string()).unwrap();
assert!(ExactLength::<3>::new("hi".to_string()).is_none());

You can compose wrappers:

use non::{NonEmpty, ASCII};

let non_empty = NonEmpty::new("hello".to_string()).unwrap();
let ascii_non_empty = ASCII::new(non_empty).unwrap();

assert_eq!(ascii_non_empty.as_ref(), "hello");

Deref and Conversion

All wrappers deref to the inner string, so you can use string methods:

use non::NonEmpty;

let s = NonEmpty::new("hello world".to_string()).unwrap();
assert!(s.contains("world"));

Convert back to String easily:

use non::NonEmpty;

let non_empty = NonEmpty::new("hello".to_string()).unwrap();
let s: String = non_empty.into();

Stripping Wrappers

Use the Strip trait to remove one wrapper layer:

use non::{NonEmpty, ASCII, Strip};

let non_empty = NonEmpty::new("hello".to_string()).unwrap();
let ascii_non_empty = ASCII::new(non_empty).unwrap();

let ascii_only = ascii_non_empty.strip();
assert_eq!(ascii_only, ASCII::new("hello".to_string()).unwrap());

no_std support

Works in no_std environments with alloc enabled:

[dependencies]
non = { version = "0.1", default-features = false }

License

Licensed under MIT. See LICENSE for details.