Rust SmartClone

Rust custom-derive macro for implementing Clone trait with more control on the fields cloned values.

use smart_clone::SmartClone;

#[derive(SmartClone)]
struct Foo {
    a: u8, // left for standard clone
    #[clone = 12]
    b: u8, // Override with hardcoded value (same as `#[clone(12)]`)
    #[clone(TEST)]
    c: u8, // In general, prefer this syntax for hardcode, variable or const
    #[clone((42, 69))]
    d: (i32, u32),
    #[clone(default)]
    e: Vec<Vec<Vec<(u8, u8)>>>, // Reserved 'skip' keyword to clone to Default::default() value (g type must implement `Default`)
    #[clone(Some(Default::default()))] // `Some(Default::default())` is not `None` but `Some(0)` !
    f: Option<i32>,
    #[clone(clone_with = "SimpleStruct::vec_clone")]
    g: Vec<u32>,
    #[clone("banana".to_owned())]
    h: String,
}

Will generate:

impl Clone for SimpleStruct {
    fn clone(&self) -> Self {
        Self {
            a: self.a.clone(),
            b: 12,
            c: TEST,
            d: (42, 69),
            e: Default::default(),
            f: Some(Default::default()),
            g: SimpleStruct::vec_clone(&self.g),
            h: "banana".to_owned(),
        }
    }
}

Install

• Add smart-clone = "0.1.0" as a dependency in Cargo.toml.
• On structs and enums that you want to clone, import the derive macro as use smart_clone::SmartClone; within the same module and write #[derive(SmartClone)] on the struct or enum.
• Use the attribute #[clone(...)] with the option you need on the desired structure field.

API options

• #[clone]: will perform cloning as usual for your field. Equivalent to no annotation.
• #[clone = xxx]: will set the value xxx to the field when the structure is cloned
• #[clone(xxx)]: same as above, but xxx can be whatever you want here, not just a literal
• #[clone(clone_with = "xxx")]: the field will be passed by reference to a function called xxx and the returned value will be used when the structure is cloned.

Examples

See the examples folder for various use cases.