# proc-macro-crate


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Providing support for `$crate` in procedural macros.

* [Introduction](#introduction)
* [Example](#example)
* [License](#license)

### 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. The returned
name of `crate_name` is either the given original rename (crate not renamed) or the renamed name.

### Example

```rust
use quote::quote;
use syn::Ident;
use proc_macro2::Span;
use proc_macro_crate::crate_name;

fn import_my_crate() {
    let name = crate_name("my-crate").expect("my-crate is present in `Cargo.toml`");
    let ident = Ident::new(&name, Span::call_site());
    quote!( extern crate #ident as my_crate_known_name );
}

```

### License

Licensed under either of

 * [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)

 * [MIT license](http://opensource.org/licenses/MIT)

at your option.

License: Apache-2.0/MIT
