cargo_meta_proc

Macro metadata

Source 
metadata!() { /* proc-macro */ }
Expand description

Macro for accessing data from the package.metadata section of the Cargo manifest

§Arguments

  • key - A string slice of a dot-separated path to the TOML key of interest

§Example

Given the following Cargo.toml:

[package]
name = "MyApp"
version = "0.1.0"

[package.metadata]
copyright = "Copyright (c) 2019 ACME Inc."

And the following main.rs:

#![feature(proc_macro_hygiene)]

use std::env;
use cargo_meta::package_metadata;

pub fn main() {
    println!("{} {}", env!("CARGO_PKG_NAME"), env!("CARGO_PKG_VERSION"));
    println!("{}", package_metadata!("copyright"));
}

Invoking cargo run will produce:

MyApp 0.1.0
Copyright (c) 2019 ACME Inc.

§TOML Support

This macro only supports static data:

  • Integers
  • Floating-point numbers
  • Booleans
  • Keys of tables nested below the package.metadata section of the manifest (if the value is a supported type)
  • Entire TOML arrays

§Array Example

Given the following Cargo manifest:

[package.metadata.arrays]
some_array = [ 1, 2, 3 ]

This is legal:

static ARR: [3; i64] = package_metadata!("arrays.some_array");

It does not currently support accessing TOML array elements directly, though this is possible. TOML tables will not be possible without a statically keyed hashmap such as the one provided by the phf crate. Support may be added if/when Rust can support static hashmaps with compile-time key errors.