build.rs

extern crate ansi_term;
extern crate version_check;

use ansi_term::Color::{Red, Yellow, Blue, White};
use version_check::{is_nightly, is_min_version, is_min_date};

// Specifies the minimum nightly version needed to compile Ion.
const MIN_DATE: &'static str = "2017-03-30";
const MIN_VERSION: &'static str = "1.18.0-nightly";

// Convenience macro for writing to stderr.
macro_rules! printerr {
    ($($arg:tt)*) => ({
        use std::io::prelude::*;
        write!(&mut ::std::io::stderr(), "{}\n", format_args!($($arg)*))
            .expect("Failed to write to stderr.")
    })
}

fn main() {
    let ok_nightly = is_nightly();
    let ok_version = is_min_version(MIN_VERSION);
    let ok_date    = is_min_date(MIN_DATE);

    let print_version_err = |version: &str, date: &str| {
        printerr!("{} {}. {} {}.",
                  White.paint("Installed version is:"),
                  Yellow.paint(format!("{} ({})", version, date)),
                  White.paint("Minimum required:"),
                  Yellow.paint(format!("{} ({})", MIN_VERSION, MIN_DATE)));
    };

    match (ok_nightly, ok_version, ok_date) {
        (Some(is_nightly), Some((ok_version, version)), Some((ok_date, date))) => {
            if !is_nightly {
                printerr!("{} {}",
                          Red.bold().paint("Error:"),
                          White.paint("Ion requires a nightly version of Rust to enable Box syntax and PEG plugins."));
                print_version_err(&*version, &*date);
                printerr!("{}{}{}",
                    Blue.paint("Use `"),
                    White.paint("rustup default nightly"),
                    Blue.paint("` to switch to a nightly compiler."));
                panic!("Aborting compilation due to incompatible compiler.")
            }

            if !ok_version || !ok_date {
                printerr!("{} {}",
                          Red.bold().paint("Error:"),
                          White.paint("Ion requires a more recent version of rustc."));
                printerr!("{}{}{}",
                          Blue.paint("Use `"),
                          White.paint("rustup update"),
                          Blue.paint("` or your preferred method to update Rust."));
                print_version_err(&*version, &*date);
                panic!("Aborting compilation due to incompatible compiler.")
            }
        },
        _ => {
            println!("cargo:warning={}", "Ion was unable to check rustc compatibility.");
            println!("cargo:warning={}", "Build may fail due to incompatible rustc version.");
        }
    }
}