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//! <div align="center"> //! <a href="https://github.com/nvzqz/cargo-emit"> //! <img src="https://raw.githubusercontent.com/nvzqz/cargo-emit/assets/logo.svg?sanitize=true" //! alt="Cargo Emit Logo" //! width="300" //! height="300"> //! </a> //! <br><br> //! <a href="https://crates.io/crates/cargo-emit"> //! <img src="https://img.shields.io/crates/d/cargo-emit.svg" //! alt="Downloads"> //! </a> //! <a href="https://travis-ci.com/nvzqz/cargo-emit"> //! <img src="https://travis-ci.com/nvzqz/cargo-emit.svg?branch=master" //! alt="Build Status"> //! </a> //! <img src="https://img.shields.io/badge/rustc-^1.37.0-blue.svg" //! alt="rustc ^1.37.0"> //! <br><br> //! </div> //! //! Talk to Cargo easily at build time, brought to you by [Nikolai Vazquez]. //! //! This library provides: //! //! - Convenience macros for communicating with Cargo during the [`build.rs`] //! phrase. Cargo listens to certain [build script outputs] that dictate how //! it should behave. //! //! - An accessible location for seeing what script build outputs are available //! to emit. //! //! - Protection against typos that can be made when printing these formatted //! outputs directly yourself. Mistyping macro names will result in a compile //! failure. //! //! # Usage //! //! This crate is available [on crates.io][crate] and can be used by adding the //! following to your project's [`Cargo.toml`]: //! //! ```toml //! [build-dependencies] //! cargo-emit = "0.1" //! ``` //! //! and something like this to your [`build.rs`]: //! //! ``` //! # let should_warn = true; //! if should_warn { //! cargo_emit::warning!("(C-3PO voice) We're doomed"); //! } //! ``` //! //! **Note:** This library is meant to be used with [Rust 2018 edition][2018], //! so that `cargo_emit::` can be used to prefix macro calls. //! //! # Compatibility //! //! This crate is compatible with Rust 1.31+ in order to use the //! `$crate::macro!` feature introduced in [Rust 2018][2018]. //! //! # Examples //! //! Very thorough examples are provided in the docs for //! [each individual macro](#macros). //! //! # Donate //! //! This project is made freely available (as in free beer), but unfortunately //! not all beer is free! So, if you would like to buy me a beer (or coffee or //! *more*), then consider supporting my work that's benefited your project //! and thousands of others. //! //! <a href="https://www.patreon.com/nvzqz"> //! <img src="https://c5.patreon.com/external/logo/become_a_patron_button.png" alt="Become a Patron!" height="35"> //! </a> //! <a href="https://www.paypal.me/nvzqz"> //! <img src="https://buymecoffee.intm.org/img/button-paypal-white.png" alt="Buy me a coffee" height="35"> //! </a> //! //! [Nikolai Vazquez]: https://twitter.com/NikolaiVazquez //! [build script outputs]: https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script //! [2018]: https://blog.rust-lang.org/2018/12/06/Rust-1.31-and-rust-2018.html#rust-2018 //! [crate]: https://crates.io/crates/cargo-emit //! [`Cargo.toml`]: https://doc.rust-lang.org/cargo/reference/manifest.html //! [`build.rs`]: https://doc.rust-lang.org/cargo/reference/build-scripts.html #![doc(html_root_url = "https://docs.rs/cargo-emit/0.1.1")] #![doc(html_logo_url = "https://raw.githubusercontent.com/nvzqz/cargo-emit/assets/logo.svg?sanitize=true")] #![deny(missing_docs)] #![no_std] mod rerun; mod rustc; /// Emits a `$key`/`$value` pair to Cargo based on [build script outputs]. /// /// This is equivalent to: /// /// ``` /// println!("cargo:$key=$value"); /// ``` /// /// This is the base macro upon which the other macros are built. /// /// # Examples /// /// This can be used to emit arbitrary user-defined metadata. /// /// ``` /// cargo_emit::pair!("root", "/path/to/root"); /// ``` /// /// The `$key` and `$value` parameters get concatenated into a single formatting /// string. Formatting runtime values can be done by passing subsequent values. /// /// ``` /// let name = "foo"; /// cargo_emit::pair!("{lib}dir", "/path/to/{lib}", lib = name); /// ``` /// /// [build script outputs]: https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script #[macro_export] macro_rules! pair { ($key:expr, $value:expr $(, $($args:tt)*)?) => { println!(concat!("cargo:", $key, "=", $value) $(, $($args)+)?) }; } /// Tells Cargo to print the formatted `warning` message. /// /// This is equivalent to: /// /// ``` /// println!("cargo:warning=$args"); /// ``` /// /// # Examples /// /// Useful for showing when something expected (but not critical) has failed. /// /// ``` /// match std::env::current_dir() { /// Ok(dir) => // ... /// # {}, /// Err(error) => cargo_emit::warning!( /// "Something suspicious is happening: {}", /// error, /// ), /// } /// ``` /// /// Assuming you're building `my-crate`, you will see: /// /// ```sh /// $ cargo build /// Compiling my-crate v0.1.0 (/path/to/my-crate) /// warning: Something suspicious is happening: ... /// ``` #[macro_export] macro_rules! warning { ($($args:tt)+) => { $crate::pair!("warning", $($args)+) }; }