src/tools/error_index_generator/build.rs

use walkdir::WalkDir;
use std::path::PathBuf;
use std::{env, fs};

fn main() {
    // The src directory (we are in src/tools/error_index_generator)
    // Note that we could skip one of the .. but this ensures we at least loosely find the right
    // directory.
    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
    let dest = out_dir.join("error_codes.rs");
    let mut idx = 0;
    for entry in WalkDir::new("../../../src") {
        let entry = entry.unwrap();
        if entry.file_name() == "error_codes.rs" {
            println!("cargo:rerun-if-changed={}", entry.path().to_str().unwrap());
            let file = fs::read_to_string(entry.path()).unwrap()
                .replace("use syntax::{register_diagnostics, register_long_diagnostics};", "")
                .replace("use syntax::register_diagnostics;", "")
                .replace("use syntax::register_long_diagnostics;", "");
            let contents = format!("(|| {{\n{}\n}})();", file);

            fs::write(&out_dir.join(&format!("error_{}.rs", idx)), &contents).unwrap();

            idx += 1;
        }
    }

    let mut all = String::new();
    all.push_str("fn register_all() -> Vec<(&'static str, Option<&'static str>)> {\n");
    all.push_str("let mut long_codes: Vec<(&'static str, Option<&'static str>)> = Vec::new();\n");
    all.push_str(r#"
macro_rules! register_diagnostics {
    ($($code:tt),*) => {{
        long_codes.extend([$(
            stringify!($code),
        )*].iter().cloned().map(|s| (s, None)).collect::<Vec<_>>());
    }};
    ($($code:tt),*,) => {{
        long_codes.extend([$(
            stringify!($code),
        )*].iter().cloned().map(|s| (s, None)));
    }}
}

macro_rules! register_long_diagnostics {
    ($($code:tt: $description:tt),*) => {
        {long_codes.extend([$(
            (stringify!($code), Some(stringify!($description))),
        )*].iter());}
    };
    ($($code:tt: $description:tt),*,) => {
        {long_codes.extend([$(
            (stringify!($code), Some(stringify!($description))),
        )*].iter());}
    }
}"#);
    for idx in 0..idx {
        all.push_str(&format!(r#"include!(concat!(env!("OUT_DIR"), "/error_{}.rs"));"#, idx));
    }
    all.push_str("\nlong_codes\n");
    all.push_str("}\n");

    fs::write(&dest, all).unwrap();
}