Crate proc_macro_crate
source · [−]Expand description
Providing support for $crate in procedural macros.
Introduction
In macro_rules! $crate is used to get the path of the crate where a macro is declared in. In
procedural macros there is currently no easy way to get this path. A common hack is to import the
desired crate with a know name and use this. However, with rust edition 2018 and dropping
extern crate declarations from lib.rs, people start to rename crates in Cargo.toml directly.
However, this breaks importing the crate, as the proc-macro developer does not know the renamed
name of the crate that should be imported.
This crate provides a way to get the name of a crate, even if it renamed in Cargo.toml. For this
purpose a single function crate_name is provided. This function needs to be called in the context
of a proc-macro with the name of the desired crate. CARGO_MANIFEST_DIR will be used to find the
current active Cargo.toml and this Cargo.toml is searched for the desired crate.
Example
use quote::quote;
use syn::Ident;
use proc_macro2::Span;
use proc_macro_crate::{crate_name, FoundCrate};
fn import_my_crate() {
let found_crate = crate_name("my-crate").expect("my-crate is present in `Cargo.toml`");
match found_crate {
FoundCrate::Itself => quote!( crate::Something ),
FoundCrate::Name(name) => {
let ident = Ident::new(&name, Span::call_site());
quote!( #ident::Something )
}
};
}
License
Licensed under either of
at your option.
Enums
Error type used by this crate.
The crate as found by crate_name.
Functions
Find the crate name for the given orig_name in the current Cargo.toml.