Crate kinded 

Kinded

Generate Rust enum kind types without boilerplate.

Get Started

use kinded::Kinded;

#[derive(Kinded)]
enum Drink {
    Mate,
    Coffee(String),
    Tea { variety: String, caffeine: bool }
}

let drink = Drink::Coffee("Espresso".to_owned());
assert_eq!(drink.kind(), DrinkKind::Coffee);

Note, the definition of DrinkKind enum is generated automatically as well as Drink::kind() method. To put it simply you get something similar to the following:

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum DrinkKind {
    Mate,
    Coffee,
    Tea
}

impl Drink {
    const fn kind(&self) -> DrinkKind {
        match self {
            Drink::Mate => DrinkKind::Mate,
            Drink::Coffee(..) => DrinkKind::Coffee,
            Drink::Tea { .. } => DrinkKind::Tea,
        }
    }
}

Const context

The kind() method is a const fn, so it can be used in const contexts:

use kinded::Kinded;

#[derive(Kinded)]
enum Status {
    Active,
    Inactive,
}

const ACTIVE_KIND: StatusKind = Status::Active.kind();

Kinded trait

The library provides Kinded trait:

pub trait Kinded {
    type Kind: PartialEq + Eq + Debug + Clone + Copy;

    fn kind(&self) -> Self::Kind;
}

From the example above, the derived implementation of Kinded for Drink resembles the following:

impl Kinded for Drink {
    type Kind = DrinkKind;

    fn kind(&self) -> DrinkKind { /* implementation */ }
}

The Kinded trait allows to build abstract functions that can be used with different enum types.

Get all kind variants

The kind type gets implementation of ::all() associated function, which returns a vector with all kind variants:

use kinded::Kinded;

#[derive(Kinded)]
enum Drink {
    Mate,
    Coffee(String),
    Tea { variety: String, caffeine: bool }
}

assert_eq!(DrinkKind::all(), [DrinkKind::Mate, DrinkKind::Coffee, DrinkKind::Tea]);

Attributes

Custom kind type name

By default the kind type name is generated by adding postfix Kind to the original enum name. This can be customized with kind = attribute:

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(kind = SimpleDrink)]
enum Drink {
    Mate,
    Coffee(String),
    Tea { variety: String, caffeine: bool }
}

assert_eq!(Drink::Mate.kind(), SimpleDrink::Mate);

Derive traits

By default the kind type implements the following traits: Debug, Clone, Copy, PartialEq, Eq, Display, FromStr, From<T>, From<&T>.

Extra traits can be derived with derive(..) attribute:

use kinded::Kinded;
use std::collections::HashSet;

#[derive(Kinded)]
#[kinded(derive(Hash))]
enum Drink {
    Mate,
    Coffee(String),
    Tea { variety: String, caffeine: bool }
}

let mut drink_kinds = HashSet::new();
drink_kinds.insert(DrinkKind::Mate);

Skip default traits

In some cases you may need to opt out of default trait implementations. For example, when using kinded with crates like enumset that provide their own trait implementations, you can use skip_derive(..) to avoid conflicts:

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(skip_derive(Display, FromStr))]
enum Task {
    Download { url: String },
    Process(Vec<u8>),
}

// Display and FromStr are not implemented for TaskKind
// You can provide your own custom implementations if needed

The following traits can be skipped:

• Derived traits: Debug, Clone, Copy, PartialEq, Eq
• Implemented traits: Display, FromStr, From

You can combine skip_derive with derive to replace default traits:

#[derive(kinded::Kinded)]
#[kinded(skip_derive(Display), derive(Hash))]
enum Expr {
    Literal(i64),
    Variable(String),
}

Generic attributes

If you’re using derive traits from other libraries like Serde or Sqlx, you might want to add extra attributes specific to those libraries. You can add these by using the attrs attribute:

use kinded::Kinded;
use serde::Serialize;
use serde_json::json;

#[derive(Kinded, Serialize)]
#[kinded(display = "snake_case", attrs(serde(rename_all = "snake_case")))]
enum Drink {
    VeryHotBlackTea,
    Milk { fat: f64 },
}

let json_value = serde_json::to_value(&DrinkKind::VeryHotBlackTea);
assert_eq!(json_value, json!("very_hot_black_tea"));

Variant attributes

You can also apply attributes to individual variants of the generated kind enum:

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(derive(Default))]
enum Priority {
    Low,
    #[kinded(attrs(default))]
    Medium,
    High,
}

// Medium is the default
assert_eq!(PriorityKind::default(), PriorityKind::Medium);

You can combine attrs with rename on the same variant:

#[derive(Kinded)]
#[kinded(derive(Default))]
enum Level {
    #[kinded(rename = "low_level", attrs(default))]
    Low,
    Medium,
}

Customize Display trait

Implementation of Display trait can be customized in the serde fashion:

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(display = "snake_case")]
enum Drink {
    VeryHotBlackTea,
    Milk { fat: f64 },
}

let tea = DrinkKind::VeryHotBlackTea;
assert_eq!(tea.to_string(), "very_hot_black_tea");

FromStr trait

The kind type implements FromStr trait. The implementation tries it’s best to parse, checking all the possible cases mentioned above.

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(display = "snake_case")]
enum Drink {
    VeryHotBlackTea,
    Milk { fat: f64 },
}

assert_eq!(
    "VERY_HOT_BLACK_TEA".parse::<DrinkKind>().unwrap(),
    DrinkKind::VeryHotBlackTea
);

assert_eq!(
    "veryhotblacktea".parse::<DrinkKind>().unwrap(),
    DrinkKind::VeryHotBlackTea
);

The possible values are "snake_case", "camelCase", "PascalCase", "SCREAMING_SNAKE_CASE", "kebab-case", "SCREAMING-KEBAB-CASE", "Title Case", "lowercase", "UPPERCASE".

Rename variants

Individual variants can have custom display/parse names using the rename attribute. This is useful when the automatic case conversion doesn’t produce the desired result:

use kinded::Kinded;

#[derive(Kinded)]
#[kinded(display = "snake_case")]
enum Validator {
    NotEmpty,
    // Without rename, this would display as "len_utf_16_min" (with extra underscore)
    #[kinded(rename = "len_utf16_min")]
    LenUtf16Min,
    #[kinded(rename = "len_utf16_max")]
    LenUtf16Max,
}

assert_eq!(ValidatorKind::NotEmpty.to_string(), "not_empty");
assert_eq!(ValidatorKind::LenUtf16Min.to_string(), "len_utf16_min");
assert_eq!(ValidatorKind::LenUtf16Max.to_string(), "len_utf16_max");

// Parsing also works with the renamed values
assert_eq!("len_utf16_min".parse::<ValidatorKind>().unwrap(), ValidatorKind::LenUtf16Min);

Note: The original variant name and its case alternatives can still be parsed (e.g., "LenUtf16Min", "len_utf_16_min").

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Thank you.

License

MIT © Serhii Potapov

Structs

ParseKindError

An error which is returned when parsing of a kind type failures.

Traits

Kind

Kinded

A trait that can be implemented by a main enum type. Typically should be derived with #[derive(kinded::Kinded)].

Derive Macros

Kinded