levitatinglion/rename-item

Procedural macro to rename items on declaration, according to different case styles

rename-item

Procedural macro to rename items on declaration, according to different case styles.

This crate provides the [macro@rename] attribute-like macro that changes the name of the item it is applied to. In order to refer to this changed name, this crate provides the [renamed!] function-like macro.

Both macros accept the same four named arguments for specifying the generated name:

• The name argument specifies the individual components the generated name will be made up of. It can be a single string literal, as in name = "foo", or a list of string literals or identifiers, as in name("foo", bar). The components are split further into individual words: name("fooBar") yields the same result as name("foo", "bar"). This split is done using the [heck] crate and follows its definition of words boundaries. The name argument is always required.

• The case argument specifies the case style the generated name will follow. It has to be a string literal, as in case = "snake". This case conversion is performed on the words extracted from the name argument; the prefix and suffix arguments explained below are not affected by the case conversion. Refer to the table below for a list of supported case styles. The case argument is always required for the [renamed!] macro; for the [macro@rename] macro a default case style can be inferred from the annotated item's type.

• The prefix argument specifies an additional string literal that is prepended to the generated name. This is done after case conversion, so that the prefix string remains fixed independent of the target case style. The prefix argument is optional and defaults to the empty string.

• The suffix argument specifies an additional string literal that is appended to the generated name. This is done after case conversion, so that the suffix string remains fixed independent of the target case style. The suffix argument is optional and defaults to the empty string.

The following case styles are supported:

Case style	case =	Example
Upper camel case	"upper_camel"	FooBar
Lower camel case	"lower_camel"	fooBar
Snake case	"snake"	foo_bar
Shouty snake case	"shouty_snake"	FOO_BAR

This crate is mainly useful when writing declarative macros, as declarative macros cannot create new identifiers. Additionally, this crate allows declarative macros to adapt a given name to various case styles, useful when the macro defines different kinds of items.

Examples

use rename_item::{rename, renamed};

// This function has the name `_return_five`
#[rename(name = "return-five", prefix = "_")]
fn foo() -> i32 {
    5
}

assert_eq!(_return_five(), 5);

// This obtains the name of the function using the macro arguments from above, and calls it
let five = renamed!(name = "return-five", case = "snake", prefix = "_")();
assert_eq!(five, 5);

Here's a concrete example, a declarative macro that defines setters for struct members:

macro_rules! struct_with_setters {
    (
        // Match a normal struct definition
        struct $name:ident {
            $($member:ident: $ty:ty),* $(,)?
        }
    ) => {
        // Emit the same struct definition
        struct $name {
            $($member: $ty,)*
        }

        // Additionally emit an impl block with a setter function for each member
        impl $name {
            $(
                #[::rename_item::rename(name($member), prefix = "set_")]
                fn foo(&mut self, val: $ty) {
                    self.$member = val;
                }
            )*
        }
    };
}

struct_with_setters! {
    struct Highscore {
        score:  i32,
        player: String,
    }
}

let mut h = Highscore {
    score:  42,
    player: "Hackerman".into(),
};
h.set_score(9001);
assert_eq!(h.score, 9001);

License

Licensed under either of MIT License or Apache License, Version 2.0 at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.