Crate enum_ext

Crate enum_ext 

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§Enum Extension Library

Rust Dependency Review Crate API

This Rust crate provides procedural and attribute macros that enhance Rust enums with additional methods and conversions. It simplifies working with enums by automatically generating utility methods for common tasks such as retrieving a list of variants, counting variants, and converting between discriminants and integer types.

See the enum_ext! and #[enum_extend] macro examples below for more information.

Both macros generate the same utility methods, so you can choose the one that best fits your coding style.

§Utility Functions

§Core Functions

  • list(): Returns an array containing all variants of the enum.
  • count(): Returns the number of variants in the enum.
  • ordinal(): Returns the ordinal (index) of a variant.
  • from_ordinal(ordinal: usize): Returns the variant corresponding to the given ordinal.
  • ref_from_ordinal(ordinal: usize): Returns a reference to the variant corresponding to the given ordinal.
  • valid_ordinal(ordinal: usize): Checks if the given ordinal is valid for the enum.
  • iter(): Returns an iterator over all the variants of the enum.
  • pretty_print(): Returns a formatted string displaying the enum and all its variants in a pretty-print format.

§String Conversion Functions

  • pascal_spaced(&self): Converts the variant name to spaced PascalCase. For instance, InQA becomes "In QA".
  • from_pascal_spaced(name: &str): Returns the variant corresponding to the spaced PascalCase name. For example, "In QA" becomes InQA.
  • snake_case(&self): Converts the variant name to snake_case. For instance, InQA becomes "in_qa".
  • from_snake_case(name: &str): Returns the variant corresponding to the snake_case name. For example, "in_qa" becomes InQA.
  • kebab_case(&self): Converts the variant name to kebab-case. For instance, InQA becomes "in-qa".
  • from_kebab_case(name: &str): Returns the variant corresponding to the kebab-case name. For example, "in-qa" becomes InQA.
  • next(&self): Returns the next variant in ordinal order (wraps around to first when at last).
  • previous(&self): Returns the previous variant in ordinal order (wraps around to last when at first).
  • next_linear(&self): Returns the next variant without wrapping (returns None at end).
  • previous_linear(&self): Returns the previous variant without wrapping (returns None at start).

§Validation Functions

  • is_first(&self): Returns true if this is the first variant (ordinal 0).
  • is_last(&self): Returns true if this is the last variant.
  • comes_before(&self, other: &Self): Returns true if this variant comes before the other in ordinal order.
  • comes_after(&self, other: &Self): Returns true if this variant comes after the other in ordinal order.

§Filtering Functions

  • variants_containing(substring: &str): Returns variants whose names contain the substring.
  • variants_starting_with(prefix: &str): Returns variants whose names start with the prefix.
  • variants_ending_with(suffix: &str): Returns variants whose names end with the suffix.

§Batch Operations

  • slice(start: usize, end: usize): Returns a slice of variants from start to end ordinal.
  • range(range: core::ops::Range<usize>): Returns variants in the specified ordinal range.
  • first_n(n: usize): Returns the first N variants.
  • last_n(n: usize): Returns the last N variants.

§Metadata Functions

  • variant_name(&self): Returns the variant name as a string.
  • variant_names(): Returns all variant names as a vector of strings.

§Random Selection (Optional Feature)

  • random(): Returns a random variant (requires "random" feature).
  • random_with_rng<R: Rng>(rng: &mut R): Returns a random variant using provided RNG (requires "random" feature).

§Integer Conversion Functions (When IntType is specified)

  • from_<IntType>(value: <IntType>) and as_<IntType>(&self): Convert to and from the specified integer type, if defined in the attributes.
    • For example, from_i32(10) and as_i32() if IntType = "i32", or from_u32(10) and as_u32() if IntType = "u32", etc.

§See examples in the repository for more information.

§Attributes

Attributes are optional and used to customize the generated methods.

  • IntType is currently the only attribute supported and specifies the discriminant type for conversion methods. The generated methods allow conversion from this type to an enum variant and vice versa. Supported types include standard Rust integer types like i32, u32, i64, etc. If this attribute is not specified, usize is used as the default.
    • Note: If the enum has discriminant values, #[derive(Clone)] is added to the enum (if not already present).

§Features

This crate supports optional features that can be enabled in your Cargo.toml:

  • random - Enables random variant selection functionality (random() and random_with_rng() methods). Add this to your Cargo.toml:
    [dependencies]
rand = "0.9"
enum_ext = { version = "0.5.1", features = ["random"] }

Assigning attributes vary slightly depending on the macro used.

When using enum_extend, the attribute is applied directly in the tag:

use enum_ext::enum_extend;

// example with no attribute
#[enum_extend]
#[derive(Debug, Clone, PartialEq)]
pub enum Discr1 {
    A = 10,
    B = 20,
    C = 30,
}

// example with an attribute
#[enum_extend(IntType = "i32")]  // <- `IntType` is the discriminant type for conversion methods
#[derive(Debug, Clone, PartialEq)]
pub enum Discr2 {
    A = 10,
    B = 20,
    C = 30,
}

When using enum_ext!, the attribute is applied in an enum_def parameter to the macro:

use enum_ext::enum_ext;

enum_ext!(
    #[enum_def(IntType = "i32")]  // <- `IntType` is the discriminant type. 
    #[derive(Debug, Clone, PartialEq)]
    pub enum AdvancedEnum {
        A = 10,  
        B = 20,
        C = 30,
    }
);

§Usage

§Using the #[enum_extend] Attribute Macro

To use the enum_extend attribute macro, simply include it in your Rust project and apply it to your enum definitions. Here’s an example:

fn main() {
    use enum_ext::enum_extend;

    #[enum_extend(IntType = "i32")]
    #[derive(Debug, Default, Clone, PartialEq)]
    pub enum AdvancedEnum {
        #[default]
        A = 10,
        B = 20,
        C = 30,
    }

    for x in AdvancedEnum::iter() {
        let i = x.as_i32();
        let v = AdvancedEnum::from_i32(i).unwrap();
        assert_eq!(i, v.as_i32());
        assert_eq!(*x, v); // This comparison requires that PartialEq be derived
    }

    let v = AdvancedEnum::from_i32(20).unwrap();
    assert_eq!(v, AdvancedEnum::B);
}

§Using the enum_ext! Procedural Macro

To use the enum_ext! macro, simply include it in your Rust project and apply it to your enum definitions. Here’s an example:

fn main() {
    use enum_ext::enum_ext;

    enum_ext!(
        #[derive(Debug, Clone, PartialEq)]
        pub enum SimpleEnum {
            A,
            B,
            C,
        }
    );
    // With this, you can now use the generated methods on SimpleEnum:
    let x = SimpleEnum::B;
    assert_eq!(x.ordinal(), 1); // B is the second variant, so its ordinal is 1

    let mut count = 0;

    // enum_ext gives enums an iterator and variants can be iterated over
    for x in SimpleEnum::iter() {
        // The ordinal of the variant can be retrieved
        let i = x.ordinal();
        assert_eq!(i, count);
        count += 1;
    }

    // enums also get a list method that returns an array of all variants
    let list = SimpleEnum::list();
    assert_eq!(list, [SimpleEnum::A, SimpleEnum::B, SimpleEnum::C]);

    enum_ext!(
        #[derive(Debug, Clone, Default, PartialEq)]
        pub enum TicketStatus {
            #[default]
            Open,
            InDev,
            Completed,
            InQA,
            CodeReview,
            FinalQA,
            FinalCodeReview,
            Accepted,
            Closed,
        }
    );

    // enums now have a pascal_spaced method that returns the variant name in spaced PascalCase.
    // This is useful for displaying enum variants in a user-friendly format (e.g., in a UI).
    // One example usage is converting InQA to "In QA" for display on a web page.
    let status = TicketStatus::InQA;
    assert_eq!(status.pascal_spaced(), "In QA");

    // enums also get a from_pascal_spaced method that returns the variant from the spaced PascalCase name.
    // This is useful for converting user-friendly format back to an enum variant.
    // This is the reverse of the example above, converting "In QA" back to an enum.
    let status2 = TicketStatus::from_pascal_spaced("In QA").unwrap();
    assert_eq!(status2, TicketStatus::InQA);
}

Additional utility methods are generated for the enum variants:

use enum_ext::enum_extend;

#[enum_extend(IntType = "i32")]
#[derive(Debug, PartialEq)]
pub enum DevelopmentStatus {
    InDev = 10,
    InQA = 20,
    CodeReview = 30,
    FinalQA = 40,
    FinalCodeReview = 50,
    Accepted = 60,
    Closed = 70,
}

fn main() {
    // Using list()
    let variants = DevelopmentStatus::list();
    assert_eq!(variants,
               [DevelopmentStatus::InDev,
                   DevelopmentStatus::InQA,
                   DevelopmentStatus::CodeReview,
                   DevelopmentStatus::FinalQA,
                   DevelopmentStatus::FinalCodeReview,
                   DevelopmentStatus::Accepted,
                   DevelopmentStatus::Closed]);

    // Using count()
    let count = DevelopmentStatus::count();
    assert_eq!(count, 7);

    // Using ordinal()
    let ordinal = DevelopmentStatus::CodeReview.ordinal();
    assert_eq!(ordinal, 2);  // CodeReview is the third variant, so its ordinal is 2
    assert_eq!(DevelopmentStatus::from_ordinal(2), Some(DevelopmentStatus::CodeReview));

    // Using iter()
    for (i, variant) in DevelopmentStatus::iter().enumerate() {
        assert_eq!(i, variant.ordinal());
    }

    // Using from_i32() and as_i32()
    let variant = DevelopmentStatus::from_i32(20).unwrap();
    assert_eq!(variant, DevelopmentStatus::InQA);
    assert_eq!(variant.as_i32(), 20);

    // Using pascal_spaced() method that returns the variant name in spaced PascalCase.
    // This is useful for displaying enum variants in a user-friendly format (e.g., in a UI).
    // One example usage is converting InQA to "In QA" for display on a web page.
    let status = DevelopmentStatus::InQA;
    assert_eq!(status.pascal_spaced(), "In QA");

    // Using from_pascal_spaced() method that returns the variant from the spaced PascalCase name.
    // This is useful for converting user-friendly format back to an enum variant.
    // This is the reverse of the example above, converting "In QA" back to an enum.
    let status2 = DevelopmentStatus::from_pascal_spaced("In QA").unwrap();
    assert_eq!(status2, DevelopmentStatus::InQA);
}

§Complex enum support

Starting with v0.5.0, enums with payloads (tuple or struct variants) are supported. These are referred to as complex enums below.

Requirements and recommendations:

  • Every complex enum variant must declare an explicit discriminant expression (for example, A(u32) = 4, B((u32, i16)) = 8). The macro will emit a compile error if any payload-carrying variant is missing a discriminant.
  • The integer representation (#[repr(..)]) is added automatically when you specify IntType, or when discriminants are present. If you do not specify IntType, the default conversion target is usize and as_usize will be generated.

What is generated for complex enums:

  • Provided methods (all const and using match on self):
    • count(), ordinal(), valid_ordinal()
    • pascal_spaced(), snake_case(), kebab_case()
    • variant_name(), is_first(), is_last(), comes_before(), comes_after()
    • as_<IntType>(&self) -> <IntType> (for example, as_u32()), which returns the discriminant value
  • Omitted methods (not generated for complex enums because they require constructing values without payloads):
    • list(), iter(), slice(), range(), first_n(), last_n()
    • from_ordinal(), ref_from_ordinal(), next(), previous(), next_linear(), previous_linear()
    • from_<IntType>(...), impl From<<IntType>> for YourEnum
    • from_pascal_spaced(…), from_snake_case(…), from_kebab_case(…), variant_names()
    • random() helpers (feature = “random”)

Example:

use enum_ext::enum_extend;

#[enum_extend(IntType = "u32")] // IntType is optional; defaults to usize when omitted
#[derive(Debug, Clone, Copy, PartialEq)]
enum Complex {
    AlphaOne(u32) = 4,
    BetaTwo((u32, i16)) = 8,
    CharlieThree { fred: u32, barny: i16 } = 16,
}

fn main() {
    let a = Complex::AlphaOne(10);
    let b = Complex::BetaTwo((1, -2));
    let c = Complex::CharlieThree { fred: 5, barny: -7 };

    // integer conversion retains match-based logic and remains const
    assert_eq!(a.as_u32(), 4);
    assert_eq!(b.as_u32(), 8);
    assert_eq!(c.as_u32(), 16);

    // ordinal and name helpers still work
    assert_eq!(a.ordinal(), 0);
    assert_eq!(a.pascal_spaced(), "Alpha One");
    assert_eq!(a.snake_case(), "alpha_one");
    assert_eq!(a.kebab_case(), "alpha-one");
}

§Changes

§v0.5.1

  • Improved internal deterministic hasher.
  • bumped dependencies.

§v0.5.0

  • Added support for complex enums (variants with payloads)
    • note: not all utility features are possible for complex enums and are omitted from these types of enums only (non-complex enums still have them). see the Complex enum support section for more details.
    use enum_ext::enum_extend;

#[enum_extend(IntType = "i32")]
#[derive(Debug, Clone, PartialEq)]
pub enum DiscrExpression {
    // singles
    X10(u32) = 10,
    // tuples
    X25((i32,i16)) = 5 * 5,
    // structs
    Y26{foo: u32,bar: String} = 13 + 13,      
}

§v0.4.5

  • Added support for discriminant expressions, instead of just literals. 
    use enum_ext::enum_extend;

#[enum_extend(IntType = "i32")]
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum DiscrExpression {
    // literals
    X10 = 10,
    // expressions
    X25 = 5 * 5,
    Y26 = 13 + 13,
    Z100 = 10 * (5 + 5),
}

§v0.4.4

  • swapped std::ops::Range with core::ops::Range for compatibility with no_std

§v0.4.3

  • as_<int_type> is now const fn if dev derives Copy on enum.

§v0.4.2

  • Parse the configured IntType into a real Rust type using syn::parse_str::<syn::Type> instead of string-based token hacks; this makes IntType handling more robust and prevents malformed type tokens from being emitted.
  • Emit #[repr(...)] whenever the user explicitly specifies IntType (even if no discriminants are present), so the enum layout matches the requested integer representation.
  • Reject multiple #[enum_def(...)] attributes on the derive macro; the macro now returns a clear compile error if more than one enum_def attribute is present.
  • Use the local EnumDefArgs::default() directly and tidy up attribute parsing code paths for clarity.
  • Improve tests and validation across the macros;

Macros§

enum_ext
Enum Extension Library

Attribute Macros§

enum_extend
Enum Extension Library