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#![no_std]
//! A simple library for applying procedural macros to a block. Simple example:
//!
//! ```
//! use cfg_block::cfg_block;
//!
//! cfg_block! {
//! if #[cfg(mips)] {
//! const STR_A: &str = "where did you get this processor";
//! const STR_B: &str = "mips just makes a good passing doctest";
//! } else {
//! const STR_A: &str = "good!";
//! const STR_B: &str = "better!";
//! }
//! }
//!
//! assert_eq!(STR_A, "good!");
//! assert_eq!(STR_B, "better!");
//! ```
//!
//! Most of the documentation is contained at [`cfg_block`], please see there
//! for more details.
// Strong clippy config
#![warn(
clippy::pedantic,
clippy::cargo,
clippy::nursery,
clippy::str_to_string,
clippy::missing_inline_in_public_items
)]
/// Allow applying inner procedural macros to a `{}` block, which helps a lot
/// with platform-based `const` values.
///
/// # Examples
///
/// Basic example handling differnt
///
/// ```
/// use cfg_block::cfg_block;
///
/// cfg_block! {
/// #[cfg(target_family = "unix")] {
/// const PLATFORM: &str = "posix !";
/// const MY_NUMBER: u8 = 5;
/// }
/// #[cfg(target_family = "windows")] {
/// const PLATFORM: &str = "windows !";
/// const MY_NUMBER: u16 = 20;
/// }
/// #[cfg(target_family = "wasm")] {
/// const PLATFORM: &str = "web !";
/// const MY_NUMBER: i32 = -5;
/// }
/// }
///
///
/// // This is a proof of concept
/// match PLATFORM {
/// "posix !" => assert_eq!(MY_NUMBER as i32, 5),
/// "windows !" => assert_eq!(MY_NUMBER as i32, 20),
/// "web !" => assert_eq!(MY_NUMBER as i32, -5),
/// &_ => panic!(),
/// }
/// ```
///
/// Or, with the if/else syntax (only works for `cfg` macros):
///
/// ```
/// use cfg_block::cfg_block;
///
/// cfg_block! {
/// if #[cfg(mips)] {
/// const STR_A: &str = "where did you get this processor";
/// const STR_B: &str = "mips just makes a good passing doctest";
/// } else {
/// const STR_A: &str = "good!";
/// const STR_B: &str = "better!";
/// }
/// }
///
/// assert_eq!(STR_A, "good!");
/// assert_eq!(STR_B, "better!");
/// ```
///
/// Currently, if/else statements need to be in a separate `cfg_block! {}` from
/// options that do not use if/else.
///
/// It is also possible to put anything that rust considers an `item` inside the
/// block. Note that this does not include `let` bindings.
///
/// ```
/// use cfg_block::cfg_block;
///
/// cfg_block! {
/// if #[cfg(mips)] {
/// const STR_A: &str = "where did you get this processor";
/// } else {
/// const STR_A: &str = "good!";
/// }
///
/// if #[cfg(not(mips))] {
/// assert_eq!(STR_A, "good!");
/// } else {}
/// }
/// ```
#[macro_export]
macro_rules! cfg_block {
// Note: we might be able to combine the `else` statement using TT munchers
// Rule for things with an else statement
// Match e.g.
// #[cfg(something)] {
// item1;
// item2;
// } else {
// item3;
// item4;
// }
//
// Replace with
// #[cfg(something)]
// item1;
// #[cfg(something)]
// item2;
// #[cfg(not(something))]
// item3;
// #[cfg(not(something))]
// item4;
(
$(
if #[cfg($meta:meta)] {
$($item:item)*
} else {
$($item_f:item)*
}
)*
) => {
$(
$(
#[cfg($meta)]
$item
)*
$(
#[cfg(not($meta))]
$item_f
)*
)*
};
// Rule for things without an else statement
// Match e.g.
// #[something] {
// item1;
// item2;
// }
//
// Replace with
// #[something]
// item1;
// #[something]
// item2;
(
$(
#[$meta:meta] {
$( $item:item )*
}
)*
) => {
$(
$(
#[$meta]
$item
)*
)*
}
}
#[cfg(test)]
mod tests {
//! Note: these tests use the (probably correct) assumption that we're not
//! testing on a mips processor
use super::*;
cfg_block! {
#[cfg(not(mips))] {
const SINGLE_A: &str = "something a";
const SINGLE_B: &str = "something b";
}
}
#[test]
fn single_validation() {
assert_eq!(SINGLE_A, "something a");
assert_eq!(SINGLE_B, "something b");
}
cfg_block! {
if #[cfg(mips)] {
const ELSE_A: &str = "nothing a";
const ELSE_B: &str = "nothing b";
} else {
const ELSE_A: &str = "something a";
const ELSE_B: &str = "something b";
}
}
#[test]
fn else_validation() {
assert_eq!(ELSE_A, "something a");
assert_eq!(ELSE_B, "something b");
}
#[test]
fn inside_item_validation() {
cfg_block! {
if #[cfg(mips)] {
assert_eq!(ELSE_A, "nothing a");
assert_eq!(ELSE_B, "nothing b");
} else {
assert_eq!(ELSE_A, "something a");
assert_eq!(ELSE_B, "something b");
}
}
}
// Currently does not work
// #[test]
// fn inside_validation() {
// // Test within a function block
// cfg_block! {
// #[cfg(mips)] {
// let inside_a: &str = "nothing a";
// let inside_b: &str = "nothing b";
// } else {
// let inside_a: &str = "something a";
// let inside_b: &str = "something b";
// }
// }
// assert_eq!(inside_a, "something a");
// assert_eq!(inside_b, "something b");
// }
}