README.md

Cornetto 🥐

This crate allow you to mutate a constant only in test configuration.

• #[cornetto(mut, 200)]: Define a constant variable mutable in test with _reset, with 200 as value
• #[cornetto(const, 200)]: Define a simple constant variable, with 200 as value

Example

use cornetto::Cornetto;

#[allow(dead_code)]
#[derive(Cornetto)]
struct Test {
    #[cornetto(mut, 200)] // mutable on test ( _reset(args...) )
    pub price: u64,
    #[cornetto(const, 150)] // always const
    pub const_price: u64,
    #[cornetto(mut, "youhouhou")]
    pub strin: String,
}

fn main() {
    println!("{}", TEST.price() == 200);
    println!("{}", TEST.const_price() == 150);
    println!("{}", TEST.strin().eq("youhouhou"));
    // true, true and true
}

#[cfg(test)]
mod test {
    #[test]
    fn test_cornetto() {
        super::TEST.price();
        assert_eq!(super::TEST.price(), 200);
        super::TEST._reset(100, "ho ho ho".to_string()); // only accessible from tests
        assert_eq!(super::TEST.price(), 100);
    }
}

How to use it

In the structure that you want to organise all your project constants, use the derive Cornetto as in the example. Define if you want to be able to mutate the identificator with keywords const and mut.

You just created a lazy_static reference of an object that have the same name of your structure but in uppercase.

If you choose the mut, you'll be able to reset it with the _reset function (only in test cfg).

/// #[cfg(test)]
mod test {
    #[test]
    fn test_cornetto() {
        super::TEST.price();
        assert_eq!(super::TEST.price(), 200);
        super::TEST._reset(100, "ho ho ho".to_string()); // only accessible from tests
        assert_eq!(super::TEST.price(), 100);
    }
}

Note that the parameters of the _reset are always the mutable identificators in order of declaration.

How it works

This procedural macro generate a new structure specially for to manage all constants and mutables. For each parameters you also get a function implemented for this structure named Cornetto${Struct_name}

impl CornettoTest {
    #[cfg(test)]
    pub fn price(&self) -> u64 {
        self.p_fields.lock().unwrap().price
    }
    pub fn const_price(&self) -> u64 {
        DEFAULT_TEST_CONST_PRICE
    }
    #[cfg(test)]
    pub fn strin(&self) -> String {
        self.p_fields.lock().unwrap().strin.to_string()
    }
    #[cfg(test)]
    pub fn _reset(&self, price: u64, strin: String) {
        let mut lock = self.p_fields.lock().unwrap();
        lock.price = price;
        lock.strin = strin;
    }
    #[cfg(not(test))]
    pub fn price(&self) -> u64 {
        DEFAULT_TEST_PRICE
    }
    #[cfg(not(test))]
    pub fn strin(&self) -> String {
        DEFAULT_TEST_STRIN.to_string()
    }
}

Get default configuration

You can allways get the default configuration on the first initialisation of the cornetto object with the function bellow. The cornetto generated structure implement the Default traits in order to initialize the static reference.

let def = CornettoTest::default()

Get constants generated

You also generate with the derive cornetto some constants.

const DEFAULT_TEST_PRICE: u64 = 200;
const DEFAULT_TEST_CONST_PRICE: u64 = 150;
const DEFAULT_TEST_STRIN: &str = "youhouhou";

Analyzer

The hygien of the crate allow you to access to anything created by the derive. But if you want to allow your IDE to see the generated functions and strutures, we have to activate the support for procedural macros and the expand of attribute macros.