wasm-bindgen/crates/web-sys/build.rs

extern crate env_logger;
#[macro_use]
extern crate failure;
extern crate wasm_bindgen_webidl;
extern crate sourcefile;

use failure::{Fail, ResultExt};
use sourcefile::SourceFile;
use std::env;
use std::ffi::OsStr;
use std::fs;
use std::path;
use std::process::{self, Command};

fn main() {
    env_logger::init();

    if let Err(e) = try_main() {
        eprintln!("Error: {}", e);
        for c in e.iter_causes() {
            eprintln!("  caused by {}", c);
        }
        process::exit(1);
    }
}

fn try_main() -> Result<(), failure::Error> {
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=webidls/enabled");

    let entries = fs::read_dir("webidls/enabled").context("reading webidls/enabled directory")?;
    let mut source = SourceFile::default();
    for entry in entries {
        let entry = entry.context("getting webidls/enabled/*.webidl entry")?;
        let path = entry.path();
        if path.extension() != Some(OsStr::new("webidl")) {
            continue
        }
        println!("cargo:rerun-if-changed={}", path.display());
        source = source.add_file(&path)
            .with_context(|_| format!("reading contents of file \"{}\"", path.display()))?;
    }

    let bindings = match wasm_bindgen_webidl::compile(&source.contents) {
        Ok(bindings) => bindings,
        Err(e) => match e.kind() {
            wasm_bindgen_webidl::ErrorKind::ParsingWebIDLSourcePos(pos) => {
                if let Some(pos) = source.resolve_offset(pos) {
                    let ctx = format!("compiling WebIDL into wasm-bindgen bindings in file \
                        \"{}\", line {} column {}", pos.filename, pos.line + 1, pos.col + 1);
                    return Err(e.context(ctx).into());
                } else {
                    return Err(e.context("compiling WebIDL into wasm-bindgen bindings").into());
                }
            }
            _ => {
                return Err(e.context("compiling WebIDL into wasm-bindgen bindings").into());
            }
        }
    };

    let out_dir = env::var("OUT_DIR").context("reading OUT_DIR environment variable")?;
    let out_file_path = path::Path::new(&out_dir).join("bindings.rs");
    fs::write(&out_file_path, bindings)
        .context("writing bindings to output file")?;

    // run rustfmt on the generated file - really handy for debugging
    if env::var("WEBIDL_RUSTFMT_BINDINGS").is_ok() {
        let status = Command::new("rustfmt")
            .arg(&out_file_path)
            .status()
            .context("running rustfmt")?;
        if !status.success() {
            bail!("rustfmt failed: {}", status)
        }
    }

    Ok(())
}