evix 2.0.0

Library-first async Nix evaluation engine
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use std::{env, fs, path::PathBuf};

const SCHEMA: &str = "schema/worker.capnp";
const CHECKED_IN_GENERATED: &str = "src/generated/worker_capnp.rs";
const GENERATED_FILE: &str = "worker_capnp.rs";

fn main() {
  println!("cargo:rerun-if-changed={SCHEMA}");
  println!("cargo:rerun-if-changed={CHECKED_IN_GENERATED}");

  let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
  let generated = out_path.join(GENERATED_FILE);

  // docs.rs does not provide the Cap'n Proto compiler. Use the checked-in
  // generated schema instead.
  if env::var("DOCS_RS").is_ok() {
    fs::copy(CHECKED_IN_GENERATED, generated)
      .expect("copy generated Cap'n Proto schema");
    return;
  }

  capnpc::CompilerCommand::new()
    .src_prefix("schema")
    .file(SCHEMA)
    .run()
    .expect("compile worker Cap'n Proto schema");

  let generated_bytes =
    fs::read(generated).expect("read generated Cap'n Proto schema");
  let checked_in_bytes = fs::read(CHECKED_IN_GENERATED).ok();
  if checked_in_bytes.as_deref() != Some(generated_bytes.as_slice()) {
    fs::write(CHECKED_IN_GENERATED, generated_bytes)
      .expect("update checked-in Cap'n Proto schema");
  }
}