Improve build.rs (#535)

grpc-testtool/build.rs

@@ -1,10 +1,24 @@
 // Copyright (C) 2023, Ava Labs, Inc. All rights reserved.
 // See the file LICENSE.md for licensing terms.
 
+use std::path::PathBuf;
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    tonic_build::compile_protos("proto/sync/sync.proto")?;
-    tonic_build::compile_protos("proto/rpcdb/rpcdb.proto")?;
-    tonic_build::compile_protos("proto/process-server/process-server.proto")?;
+    // we want to import these proto files
+    let import_protos = ["sync", "rpcdb", "process-server"];
+
+    let protos: Box<[PathBuf]> = import_protos
+        .into_iter()
+        .map(|proto| PathBuf::from(format!("proto/{proto}/{proto}.proto")))
+        .collect();
+
+    // go through each proto and build it, also let cargo know we rerun this if the file changes
+    for proto in protos.iter() {
+        tonic_build::compile_protos(proto)?;
+
+        // this improves recompile times; we only rerun tonic if any of these files change
+        println!("cargo:rerun-if-changed={}", proto.display());
+    }
 
     Ok(())
 }