Nestify

Nestify is a Rust library offering a powerful macro to streamline the definition of nested structs and enums. Designed to improve code readability and maintainability

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Abstract

Nestify re-imagines Rust struct and enum definitions with its "Type is Definition" approach, streamlining the way you handle nested structures. Gone are the days of flipping back and forth between type definitions—Nestify Unifies your codebase, making your code cleaner and far more readable.

Nestify is crafted for ease of learning, with its syntax tailored to be comfortable for Rust developers. The aim is for anyone, even those unfamiliar with the Nest macro, to quickly grasp its concept upon first glance.

Features

• Simplify nested struct and enum definitions in Rust.
• Make your codebase more readable and less verbose.
• Ideal for modeling complex API responses.
• Advanced attribute modifiers.
• Works well with Serde.
• Intuitive syntax

Installation

Add this to your Cargo.toml:

[dependencies]
nestify = "0.3.3"

Then use the macro:

use nestify::nest;

[!NOTE] A nightly toolchain might provide better error diagnostics

Quick Examples

Simple Nested Structures

Here's a quick example to show how Nestify simplifies nested struct definitions:

// Define a user profile with nested address and preferences structures
nest! {
    struct UserProfile {
        name: String,
        address: struct Address {
            street: String,
            city: String,
        },
        preferences: struct Preferences {
            newsletter: bool,
        },
    }
}

<details class="expand"> <summary> Expand </summary> <br>

struct UserProfile {
    name: String,
    address: Address,
    preferences: Preferences,
}

struct Address {
    street: String,
    city: String,
}

struct Preferences {
    newsletter: bool,
}

</details>

Simple Nested Enums

// Define a task with a nested status enum
nest! {
    struct Task {
        id: i32,
        description: String,
        status: enum Status {
            Pending,
            InProgress,
            Completed,
        },
    }
}

<details class="expand"> <summary> Expand </summary> <br>

struct Task {
    id: i32,
    description: String,
    status: Status,
}

enum Status {
    Pending,
    InProgress,
    Completed,
}

</details>

Supported definitions

Nestify supports both structs and enums.

// field structs (named)
nest! {
    struct Named {
        f: struct Nested {}
    }
}

// tuple structs (unnamed)
nest! {
    struct Unnamed(struct Nested())
}

// unit structs
nest! {
    struct Unit {
        unit: struct UnitStruct
    }
}


// enums
nest! {
    enum EnumVariants {
        Unit,
        Tuple(i32, struct TupleNested),
        Struct {
            f1: i32,

        }
        DiscriminantVariant = 1,
    }
}
// note: any variant can have a discriminant
// just as in normal rust

<details class="expand"> <summary> Expand </summary> <br>

// field structs (named)
struct Named {
    f: Nested,
}
struct Nested {}

// tuple structs (unnamed)
struct Unnamed(Nested,);
struct Nested();

// unit structs
struct Unit {
    unit: UnitStruct,
}
struct UnitStruct;


// enums
enum EnumVariants {
    Unit,
    Tuple(i32, TupleNested),
    Struct { 
        f1: i32 
    },
    DiscriminantVariant = 1,
}
struct TupleNested;

</details>

Generics

Nestify fully supports Rust's generic parameters. This compatibility ensures that you can incorporate both lifetime and type parameters within your nested struct definitions, just as you would in standard Rust code.

nest! {
    struct Example<'a, T> {
        s: &'a str,
        t: T
    }
}

<details class="expand"> <summary> Expand </summary> <br>

struct Example<'a, T> { 
    s: &'a str, 
    t: T, 
}

</details>

Nested Generics

When defining nested generics, you need to add generics to types. Enter "FishHook" syntax. To define generics on the field use ||<...>. This will let you specify the nested generic types. It also works with lifetimes if needed.

nest! {
    struct Parent<'a> {
        child : struct Child<'c, C> {
            s: &'c str,
            f: C
        } ||<'a, i32>
    }
}

<details class="expand"> <summary> Expand </summary> <br>

struct Parent<'a> {
    child: Child<'a, i32>,
    //           ^^^^^^^^ FishHook expands to this part
}

struct Child<'c, C> {
    s: &'c str,
    f: C,
}

</details>

Attributes

You can apply attributes just like you would with a normal struct.

nest! {
    #[derive(Clone)]
    struct CloneMe {}
}

let x = CloneMe {};
let cl = x.clone();

Recursive Attributes #[meta]*

Using * syntax you can inherit attributes to child structures easily. The attribute will propagate to each nested structure or enum.

nest! {
    #[apply_all]*
    struct One {
        two: struct Two {
            three: struct Three {
                payload: ()
            }
        }
    }
}

<details class="expand"> <summary> Expand </summary> <br>

#[apply_all]
struct One {
    two: Tow,
}

#[apply_all]
struct Two {
    three: Three,
}

#[apply_all]
struct Three {
    payload: (),
}

</details>

Removal Syntax

Disable Propagation #[meta]/

You can end the recursion of an attribute with a / attribute modifier. It will remove a recursive attribute from the current structure and all nested structures

nest! {
    #[nest]*
    struct One {
        two: struct Two {
            three: #[nest]/ 
            struct Three {
                four: struct Four { }
            }
        }
    }
}

<details class="expand"> <summary> Expand </summary> <br>

#[nest]
struct One {
    two: Two,
}

#[nest]
struct Two {
    three: Three,
}

struct Three {
    four: Four,
}

struct Four {}

</details>

Disable Single #[meta]-

Using the - modifier will remove a recursive attribute from a single structure To use the previous example using - instead of /:

nest! {
    #[nest]*
    struct One {
        two: struct Two {
            three: #[nest]- 
            struct Three {
                four: struct Four { }
            }
        }
    }
}

<details class="expand"> <summary> Expand </summary> <br>

#[nest]
struct One {
    two: Two,
}

#[nest]
struct Two {
    three: Three,
}

struct Three {
    four: Four,
}

#[nest]
struct Four {}

</details>

Field Attributes #>[meta]

If you structure has many defined attributes, it can become awkward to define attributes before the nested structure. To combat this, you can define attributes that apply to nested objects before fields and enum variants. This can be accomplished by using #>[meta] syntax. #> will apply the attribute to the next struct.

nest! {
    struct MyStruct {
        #>[derive(Debug)]
        f: struct DebugableStruct { } 
        // equivlent to: 
        // f: #[derive(Debug)]
        // struct DebugableStruct { }
    }
}

<details class="expand"> <summary> Expand </summary> <br>

struct MyStruct {
    f: DebugableStruct,
}

#[derive(Debug)]
//       ^^^^^ applied to structure and not field `f`
struct DebugableStruct {}

</details>

Enum Variant Attributes

Field attributes can also be applied to an enum variant. If there are multiple items defined in a single variant then the attribute will be applied to each.

nest! {
    enum MyEnum {
        #>[derive(Debug)]
        Variant {
            // #[derive(Debug)
            one: struct One,
            // #[derive(Debug)
            two: struct Two
        }
    }
}

<details class="expand"> <summary> Expand </summary> <br>

enum MyEnum {
    Variant {
        one: One,
        two: Two,
    }
}

#[derive(Debug)]
struct One;

#[derive(Debug)]
struct Two;

</details>

Semicolons

Rust mandates semicolons to mark the end of tuple struct and unit struct declarations. Nestify, however, introduces flexibility by making this semicolon optional.

Rust Standard

• Tuple struct: struct MyTuple(i32, String);
• Unit struct: struct MyUnit;

Nestify Flexibility

With Nestify, you can omit the semicolon without any impact:

// Unit struct without a semicolon
nest! {
    struct MyUnit
}

// Tuple struct without a semicolon
nest! {
    struct MyTuple(i32, String)
}

<details class="expand"> <summary> Expand </summary> <br>

struct MyUnit;
//           ^ automaticly added

struct MyTuple(i32, String);
//                         ^ automaticly added

</details> <br>

This adjustment simplifies syntax, particularly in the context of defining nested structures, aligning with Nestify's goal of enhancing code readability and maintenance. Whether you include the semicolon or not, Nestify processes the definitions correctly, thanks to its domain-specific optimizations.

Visibility

Visibility can be altered in both parent and nested structures. It exhibits the following behavior

Named Field Visibility

When using named fields, you must specify the desired vi