Whole project rebuilds every time

[koxu1996]

Project build cache is broken when using tonic-buf-build in build.rs, for example:

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

  let out_dir = PathBuf::from(std::env::var("OUT_DIR").unwrap());
  let mut config = prost_build::Config::new();

  tonic_buf_build::compile_from_buf_workspace(
    tonic_build::configure().build_client(true).out_dir(out_dir),
    Some(config),
  )
  .unwrap();
}

Even with no changes, every cargo build takes few seconds and it runs build script again... That makes this library unusable, as it basically breaks the responsivness of IDE's intellisense.

[koxu1996]

I tracked down the issue:

1. Function compile_from_buf_workspace_with_config composes includes vector with the following paths:

• export dir - temdir() output - for example /tmp/7fb04eec-5c56-47f5-b47d-979db5ecf677,
• all user directories, from buf.work.yaml.

2. Tonic builder gets called, includes are passed:

tonic-buf-build/src/lib.rs

Line 125 in 7bdce02

Some(config) => tonic_builder.compile_protos_with_config(config, &protos, &includes),

3. Tonic builder emits cargo:rerun-if-changed={} for all includes - also for the temp dir ❗❗❗

4. Tempdir gets removed after successful compilation, and cargo consider removed file as changed.

[koxu1996]

I think the best solution here is to avoid passing export dir as include, but rather gather a list of individual protos.

As a temporary workaround I configured client with emit_rerun_if_changed(false) and hardcoded appropriate reruns for my protos.