Refined Type

---

refined_type is a library developed for Rust. It enhances your types, making them more robust and expanding the range of guarantees your applications can statically ensure.

You can create various rules for a certain type, such as phone numbers, addresses, times, and so on. Once you have established the rules, you can easily combine them. Specifically, if you create rules for 'non-empty strings' and 'strings composed only of alphabets,' you do not need to redefine a new rule for 'non-empty strings composed only of alphabets'. All rules can be arbitrarily combined and extended as long as the target type matches. Enjoy a wonderful type life!

Installation

cargo add refined_type

Get Started

As an example, let's convert from JSON to a struct.

// define a struct for converting from JSON.
#[derive(Debug, Deserialize)]
struct Human {
    name: NonEmptyString,
    age: MinMaxU8<18, 80>,
    friends: NonEmptyVec<String>,
}

// In the 1st example, all fields satisfy the rule, causing the conversion from JSON to succeed.
fn get_started_simple_example() -> anyhow::Result<()> {
    let json = json! {{
        "name": "john",
        "age": 20,
        "friends": ["tom", "taro"]
    }}
        .to_string();

    let human = serde_json::from_str::<Human>(&json)?;

    assert_eq!(human.name.into_value(), "john");
    assert_eq!(human.age.into_value(), 20);
    assert_eq!(human.friends.into_value(), vec!["tom", "taro"]);
    Ok(())
}

// In the 2nd example, while `name` does not satisfy the rule, `age` and `friends` do, causing the conversion from JSON to fail.
fn get_started_empty_name_example() -> anyhow::Result<()> {
    let json = json! {{
        "name": "",
        "age": 20,
        "friends": ["tom", "taro"]
    }}
        .to_string();

    // because `name` is empty
    assert!(serde_json::from_str::<Human>(&json).is_err());
    Ok(())
}

// In the 3rd example, while `age` does not satisfy the rule, `name` and `friends` do, causing the conversion from JSON to fail.
fn get_started_outbound_age_example() -> anyhow::Result<()> {
    let json = json! {{
        "name": "john",
        "age": 100,
        "friends": ["tom", "taro"]
    }}
        .to_string();

    // because `age` is not in the range of 18 to 80
    assert!(serde_json::from_str::<Human>(&json).is_err());
    Ok(())
}

// In the 4th example, while `friends` does not satisfy the rule, `name` and `age` do, causing the conversion from JSON to fail.
fn get_started_empty_vec_example() -> anyhow::Result<()> {
    let json = json! {{
        "name": "john",
        "age": 20,
        "friends": []
    }}
        .to_string();

    // because `friends` is empty
    assert!(serde_json::from_str::<Human>(&json).is_err());
    Ok(())
}

---

Compose Rules

As mentioned earlier, it is possible to combine any rules as long as the target types match. In the example below, there are standalone rules for 'strings containing Hello' and 'strings containing World'. Since their target type is String, combining them is possible. I have prepared something called Rule Composer (And, Or, Not). By using Rule Composer, composite rules can be easily created.

1: And Rule Composer

And Rule Composer is a rule that satisfies both of the two rules. It is generally effective when you want to narrow down the condition range.

type Target = Refined<And![EvenRuleU8, MinMaxRuleU8<0, 100>]>;

fn and_example() -> Result<(), Error<u8>> {
    let target = Target::new(50)?;
    assert_eq!(target.into_value(), 50);

    let target = Target::new(51);
    assert!(target.is_err());

    Ok(())
}

2: Or Rule Composer

Or Rule Composer is a rule that satisfies either of the two rules. It is generally effective when you want to expand the condition range.

type Target = Refined<Or![LessRuleU8<10>, GreaterRuleU8<50>]>;

fn or_example() -> Result<(), Error<u8>> {
    let target = Target::new(5)?;
    assert_eq!(target.into_value(), 5);

    let target = Target::new(10);
    assert!(target.is_err());

    let target = Target::new(50);
    assert!(target.is_err());

    let target = Target::new(51)?;
    assert_eq!(target.into_value(), 51);

    Ok(())
}

3: Not Rule Composer

Not Rule Composer is a rule that does not satisfy a specific condition. It is generally effective when you want to discard only certain situations.

type Target = Refined<Not<EqualRuleU8<50>>>;

fn not_example() -> Result<(), Error<u8>> {
    let target = Target::new(49)?;
    assert_eq!(target.into_value(), 49);

    let target = Target::new(50);
    assert!(target.is_err());

    let target = Target::new(51)?;
    assert_eq!(target.into_value(), 51);

    Ok(())
}

4: If Rule Composer

If Rule Composer is a rule that applies a specific rule only when a certain condition is met.

type Target = Refined<If<GreaterEqualRuleI8<10>, EvenRuleI8>>;

fn if_example() -> Result<(), Error<i8>> {
    let target = Target::new(8)?;
    assert_eq!(target.into_value(), 8);

    let target = Target::new(9)?;
    assert_eq!(target.into_value(), 9);

    let target = Target::new(10)?;
    assert_eq!(target.into_value(), 10);

    let target = Target::new(11);
    assert!(target.is_err());

    Ok(())
}

5: IfElse Rule Composer

IfElse Rule Composer is a rule that applies a specific rule when a certain condition is met and another rule when it is not met.

type Target = Refined<IfElse<GreaterEqualRuleI8<10>, EvenRuleI8, OddRuleI8>>;

fn if_else_example() -> Result<(), Error<i8>> {
    let target = Target::new(8);
    assert!(target.is_err());

    let target = Target::new(9)?;
    assert_eq!(target.into_value(), 9);

    let target = Target::new(10)?;
    assert_eq!(target.into_value(), 10);

    let target = Target::new(11);
    assert!(target.is_err());

    Ok(())
}

6: Other Rule Composer

Equiv, Nand, Nor and Xor are also available.

Number

MinMax

MinMax is a type that signifies the target exists between a certain number and another number.

type Age = MinMaxU8<18, 80>;

fn min_max_example() -> Result<(), Error<u8>> {
    let age = Age::new(18)?;
    assert_eq!(age.into_value(), 18);

    let age = Age::new(80)?;
    assert_eq!(age.into_value(), 80);

    let age = Age::new(17);
    assert!(age.is_err());

    let age = Age::new(81);
    assert!(age.is_err());
    Ok(())
}

Less

Less is a type that signifies the target is less than a certain number.

type Age = LessU8<80>;

fn less_example() -> Result<(), Error<u8>> {
    let age = Age::new(79)?;
    assert_eq!(age.into_value(), 79);

    let age = Age::new(80);
    assert!(age.is_err());

    Ok(())
}

Greater

Greater is a type that signifies the target is greater than a certain number.

type Age = GreaterU8<18>;

fn greater_example() -> Result<(), Error<u8>> {
    let age = Age::new(19)?;
    assert_eq!(age.into_value(), 19);

    let age = Age::new(18);
    assert!(age.is_err());

    Ok(())
}

Equal

Equal is a type that signifies the target is equal to a certain number.

type Age = EqualU8<18>;

fn equal_example() -> Result<(), Error<u8>> {
    let age = Age::new(18)?;
    assert_eq!(age.into_value(), 18);

    let age = Age::new(19);
    assert!(age.is_err());

    Ok(())
}

LessEqual

LessEqual is a type that signifies the target is less than or equal to a certain number.

type Age = LessEqualU8<80>;

fn less_equal_example() -> Result<(), Error<u8>> {
    let age = Age::new(79)?;
    assert_eq!(age.into_value(), 79);

    let age = Age::new(80)?;
    assert_eq!(age.into_value(), 80);

    let age = Age::new(81);
    assert!(age.is_err());

    Ok(())
}

GreaterEqual

GreaterEqual is a type that signifies the target is greater than or equal to a certain number.

type Age = GreaterEqualU8<18>;

fn greater_equal_example() -> Result<(), Error<u8>> {
    let age = Age::new(19)?;
    assert_eq!(age.into_value(), 19);

    let age = Age::new(18)?;
    assert_eq!(age.into_value(), 18);

    let age = Age::new(17);
    assert!(age.is_err());

    Ok(())
}

Range

Range is a type that signifies the target exists between a certain number and another number.

type Age = RangeU8<18, 80>;

fn range_example() -> Result<(), Error<u8>> {
    let age = Age::new(17);
    assert!(age.is_err());

    let age = Age::new(18)?;
    assert_eq!(age.into_value(), 18);

    let age = Age::new(79)?;
    assert_eq!(age.into_value(), 79);

    let age = Age::new(80);
    assert!(age.is_err());

    Ok(())
}

Iterator

refined_type has several useful refined types for Iterators.

ForAll

ForAll is a rule that applies a specific rule to all elements in the Iterator.

fn example_11() -> anyhow::Result<()> {
    let vec = vec!["Hello".to_string(), "World".to_string()];
    let for_all_ok = ForAllVec::<NonEmptyStringRule>::new(vec.clone())?;
    assert_eq!(vec, for_all_ok.into_value());

    let vec = vec!["Hello".to_string(), "".to_string()];
    let for_all_err = ForAllVec::<NonEmptyStringRule>::new(vec.clone());
    assert!(for_all_err.is_err());
    Ok(())
}

Exists

Exists is a rule that applies a specific rule to at least one element in the Iterator.

fn example_12() -> anyhow::Result<()> {
    let vec = vec!["Hello".to_string(), "".to_string()];
    let exists_ok = ExistsVec::<NonEmptyStringRule>::new(vec.clone())?;
    assert_eq!(vec, exists_ok.into_value());

    let vec = vec!["".to_string(), "".to_string()];
    let exists_err = ExistsVec::<NonEmptyStringRule>::new(vec.clone());
    assert!(exists_err.is_err());
    Ok(())
}

Head

Head is a rule that applies a specific rule to the first element in the Iterator.

fn example_13() -> anyhow::Result<()> {
    let table = vec![
        (vec!["good morning".to_string(), "".to_string()], true), // PASS
        (vec!["hello".to_string(), "hello".to_string()], true),   // PASS
        (vec![], false),                                          // FAIL
        (vec!["".to_string()], false),                            // FAIL
        (vec!["".to_string(), "hello".to_string()], false),       // FAIL
    ];

    for (value, ok) in table {
        let head = HeadVec::<NonEmptyStringRule>::new(value.clone());
        assert_eq!(head.is_ok(), ok);
    }

    Ok(())
}

Last

Last is a rule that applies a specific rule to the last element in the Iterator.

fn example_14() -> anyhow::Result<()> {
    let table = vec![
        (vec!["".to_string(), "hello".to_string()], true), // PASS
        (vec!["good morning".to_string(), "hello".to_string()], true), // PASS
        (vec![], false),                                   // FAIL
        (vec!["".to_string()], false),                     // FAIL
        (vec!["hello".to_string(), "".to_string()], false), // FAIL
    ];

    for (value, ok) in table {
        let last = LastVec::<NonEmptyStringRule>::new(value.clone());
        assert_eq!(last.is_ok(), ok);
    }

    Ok(())
}

Tail

Tail is a rule that applies a specific rule to all elements except the first element in the Iterator.

fn example_15() -> anyhow::Result<()> {
    let table = vec![
        (vec!["hey".to_string(), "hello".to_string(), "world".to_string()], true),
        (vec!["hey".to_string(), "hello".to_string(), "".to_string()], false),
        (vec!["hey".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["hey".to_string(), "".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string(), "world".to_string()], true),
        (vec!["".to_string(), "hello".to_string(), "".to_string()], false),
        (vec!["".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["".to_string(), "".to_string(), "".to_string()], false),
    ];

    for (value, ok) in table {
        let tail = TailVec::<NonEmptyStringRule>::new(value.clone());
        assert_eq!(tail.is_ok(), ok);
    }

    Ok(())
}

Init

Init is a rule that applies a specific rule to all elements except the last element in the Iterator.

fn example_16() -> anyhow::Result<()> {
    let table = vec![
        (vec!["hey".to_string(), "hello".to_string(), "world".to_string()], true),
        (vec!["hey".to_string(), "hello".to_string(), "".to_string()], true),
        (vec!["hey".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["hey".to_string(), "".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string(), "world".to_string()], false),
        (vec!["".to_string(), "hello".to_string(), "".to_string()], false),
        (vec!["".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["".to_string(), "".to_string(), "".to_string()], false),
    ];

    for (value, ok) in table {
        let init = InitVec::<NonEmptyStringRule>::new(value.clone());
        assert_eq!(init.is_ok(), ok);
    }

    Ok(())
}

Index

Index is a rule that applies a specific rule to the element at a specific index in the Iterator.

fn example_17() -> anyhow::Result<()> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], true),
        (vec!["good morning".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], false),
    ];

    for (value, expected) in table {
        let refined = IndexVec::<1, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

CountEqual

CountEqual is a type that signifies the number of elements that satisfy the rule is a specific number.

fn count_equal_example() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], false),
        (vec!["good morning".to_string(), "".to_string()], true),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], false),
    ];

    for (value, expected) in table {
        let refined = CountEqualVec::<1, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

CountLess

CountLess is a type that signifies the number of elements that satisfy the rule is less than a specific number.

fn count_less_example() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], false),
        (vec!["good morning".to_string(), "".to_string()], true),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], true),
    ];

    for (value, expected) in table {
        let refined = CountLessVec::<2, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

CountGreater

CountGreater is a type that signifies the number of elements that satisfy the rule is greater than a specific number.

fn count_greater_example() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], true),
        (vec!["good morning".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string()], false),
        (vec!["".to_string(), "".to_string()], false),
    ];

    for (value, expected) in table {
        let refined = CountGreaterVec::<1, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

CountLessEqual

CountLessEqual is a type that signifies the number of elements that satisfy the rule is less than or equal to a specific number.

fn count_less_equal_example() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], true),
        (vec!["good morning".to_string(), "".to_string()], true),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], true),
    ];

    for (value, expected) in table {
        let refined = CountLessEqualVec::<2, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

CountGreaterEqual

CountGreaterEqual is a type that signifies the number of elements that satisfy the rule is greater than or equal to a specific number.

fn count_greater_equal_example() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], true),
        (vec!["good morning".to_string(), "".to_string()], true),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], false),
    ];

    for (value, expected) in table {
        let refined = CountGreaterEqualVec::<1, NonEmptyStringRule>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

Reverse

Reverse is a rule that applies a specific rule to all elements in the Iterator in reverse order.

fn example_18() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["good morning".to_string(), "hello".to_string()], true),
        (vec!["good morning".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string()], true),
        (vec!["".to_string(), "".to_string()], false),
    ];

    for (value, expected) in table {
        let refined = Reverse::<IndexRuleVec<0, NonEmptyStringRule>>::new(value.clone());
        assert_eq!(refined.is_ok(), expected);
    }

    Ok(())
}

Skip

Skip is a rule that applies a specific rule to the elements of the Iterator while skipping the elements according to SkipOption.

fn example_19() -> Result<(), Error<Vec<i32>>> {
    let table = vec![
        (vec!["hey".to_string(), "hello".to_string(), "world".to_string()], true),
        (vec!["hey".to_string(), "hello".to_string(), "".to_string()], false),
        (vec!["hey".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["hey".to_string(), "".to_string(), "".to_string()], false),
        (vec!["".to_string(), "hello".to_string(), "world".to_string()], true),
        (vec!["".to_string(), "hello".to_string(), "".to_string()], false),
        (vec!["".to_string(), "".to_string(), "world".to_string()], false),
        (vec!["".to_string(), "".to_string(), "".to_string()], false),
    ];

    for (value, ok) in table {
        let init = SkipVec::<NonEmptyStringRule, SkipFirst<_>>::new(value.clone());
        assert_eq!(init.is_ok(), ok);
    }

    Ok(())
}

if you need more skip option, you can define it like this.

pub struct NoSkip<T> {
    _phantom_data: std::marker::PhantomData<T>,
}

impl<ITEM> SkipOption for NoSkip<ITEM> {
    type Item = ITEM;
    type Accumulator = ();
    fn should_skip(_: usize, _: Option<&mut Self::Accumulator>, _: &Self::Item) -> bool {
        false
    }
}

Length

You can impose constraints on objects that have a length, such as String or Vec.

LengthMinMax

LengthMinMax is a type that signifies the target has a length between a certain number and another number.

fn length_min_max_example() -> Result<(), Error<String>> {
    type Password = LengthMinMax<5, 10, String>;

    let password = Password::new("123456".to_string())?;
    assert_eq!(password.into_value(), "123456");

    let password = Password::new("1234".to_string());
    assert!(password.is_err());

    let password = Password::new("12345678901".to_string());
    assert!(password.is_err());

    Ok(())
}

LengthGreater

LengthGreater is a type that signifies the target has a length greater than a certain number.

fn length_greater_example() -> Result<(), Error<String>> {
    type Password = LengthGreater<5, String>;

    let password = Password::new("123456".to_string())?;
    assert_eq!(password.into_value(), "123456");

    let password = Password::new("1234".to_string());
    assert!(password.is_err());

    Ok(())
}

LengthLess

LengthLess is a type that signifies the target has a length less than a certain number.

fn length_less_example() -> Result<(), Error<String>> {
    type Password = LengthLess<10, String>;

    let password = Password::new("123456".to_string())?;
    assert_eq!(password.into_value(), "123456");

    let password = Password::new("12345678901".to_string());
    assert!(password.is_err());

    Ok(())
}

LengthEqual

LengthEqual is a type that signifies the target has a length equal to a certain number.

fn length_equal_example() -> Result<(), Error<String>> {
    type Password = LengthEqual<5, String>;

    let password = Password::new("12345".to_string())?;
    assert_eq!(password.into_value(), "12345");

    let password = Password::new("1234".to_string());
    assert!(password.is_err());

    Ok(())
}

Custom Length

You can define a length for any type. Therefore, if you want to implement a length that is not provided by refined_type, you can easily do so using LengthDefinition.

#[derive(Debug, PartialEq)]
struct Hello;
impl LengthDefinition for Hello {
    fn length(&self) -> usize {
        5
    }
}

fn custom_length_example() -> Result<(), Error<Hello>> {
    let hello = Refined::<LengthEqualRule<5, Hello>>::new(Hello)?;
    assert_eq!(hello.into_value(), Hello);
    Ok(())
}

JSON

refined_type is compatible with serde_json. This ensures type-safe communication and eliminates the need to write new validation processes. All you need to do is implement a set of rules once and implement serde’s Serialize and Deserialize.

Serialize

#[derive(Debug, Eq, PartialEq, Deserialize, Serialize)]
struct Human2 {
    name: NonEmptyString,
    age: u8,
}

fn example_9() -> anyhow::Result<()> {
    let john = Human2 {
        name: NonEmptyString::new("john".to_string())?,
        age: 8,
    };

    let actual = json!(john);
    let expected = json! {{
        "name": "john",
        "age": 8
    }};
    assert_eq!(actual, expected);
    Ok(())
}

Deserialize

fn example_10() -> anyhow::Result<()> {
    let json = json! {{
        "name": "john",
        "age": 8
    }}
        .to_string();

    let actual = serde_json::from_str::<Human2>(&json)?;

    let expected = Human2 {
        name: NonEmptyString::new("john".to_string())?,
        age: 8,
    };
    assert_eq!(actual, expected);
    Ok(())
}