fix(build): honor PROTOC when generating protobuf code (#4441)

The core, server, and sandbox-backend build scripts always used the vendored protoc binary and ignored PROTOC, so a distro build could not use its system compiler. When PROTOC is set, use it and let prost resolve the includes (PROTOC_INCLUDE still applies); otherwise behave exactly as before. Contributes to #3510.

Signed-off-by: politerealism <burdcat17@gmail.com>

crates/openshell-core/build.rs

@@ -9,10 +9,18 @@ mod build_version;
 const PROTO_REL: &str = "../../proto";
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    // Preserve the vendored include-tree guarantee even when the caller has
-    // PROTOC_INCLUDE set: prost validates that ambient path independently of
-    // explicit includes. Re-enter with a child-only environment override.
-    if env::var_os("PROTOC_INCLUDE").is_some() {
+    // A caller-supplied PROTOC (for example a distro package's system
+    // compiler) is used as-is and prost resolves its own includes. Without it,
+    // use the vendored compiler and include tree.
+    println!("cargo:rerun-if-env-changed=PROTOC");
+    println!("cargo:rerun-if-env-changed=PROTOC_INCLUDE");
+    let use_vendored_protoc = env::var_os("PROTOC").is_none();
+
+    // In vendored mode, preserve the vendored include-tree guarantee even when
+    // the caller has PROTOC_INCLUDE set: prost validates that ambient path
+    // independently of explicit includes. Re-enter with a child-only
+    // environment override.
+    if use_vendored_protoc && env::var_os("PROTOC_INCLUDE").is_some() {
         let status = std::process::Command::new(env::current_exe()?)
             .env_remove("PROTOC_INCLUDE")
             .status()?;
@@ -40,10 +48,15 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     // Re-run when anything under proto/ changes (including newly added .proto files).
     println!("cargo:rerun-if-changed={PROTO_REL}");
     // Configure the vendored compiler and well-known includes without changing
-    // the build process environment.
+    // the build process environment. With a caller-supplied PROTOC, leave both
+    // to prost.
     let mut proto_config = tonic_prost_build::Config::new();
-    proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
-    let proto_include = protoc_bin_vendored::include_path()?;
+    let proto_include = if use_vendored_protoc {
+        proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
+        Some(protoc_bin_vendored::include_path()?)
+    } else {
+        None
+    };
 
     let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR")?);
     let proto_root = manifest_dir.join(PROTO_REL);
@@ -53,6 +66,8 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let out_dir = PathBuf::from(env::var("OUT_DIR")?);
     let descriptor_path = out_dir.join("openshell_descriptor.bin");
+    let mut include_dirs = vec![proto_root];
+    include_dirs.extend(proto_include);
 
     // Configure tonic/prost protobuf code generation.
     tonic_prost_build::configure()
@@ -62,7 +77,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         // Emit a binary FileDescriptorSet so the server can enumerate every
         // RPC at runtime (used by the per-handler auth exhaustiveness test).
         .file_descriptor_set_path(&descriptor_path)
-        .compile_with_config(proto_config, &proto_files, &[proto_root, proto_include])?;
+        .compile_with_config(proto_config, &proto_files, &include_dirs)?;
 
     println!(
         "cargo:rustc-env=OPENSHELL_DESCRIPTOR_PATH={}",

crates/openshell-sandbox-backend/build.rs

@@ -2,10 +2,18 @@
 // SPDX-License-Identifier: Apache-2.0
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    // Preserve the vendored include-tree guarantee even when the caller has
-    // PROTOC_INCLUDE set: prost validates that ambient path independently of
-    // explicit includes. Re-enter with a child-only environment override.
-    if std::env::var_os("PROTOC_INCLUDE").is_some() {
+    // A caller-supplied PROTOC (for example a distro package's system
+    // compiler) is used as-is and prost resolves its own includes. Without it,
+    // use the vendored compiler and include tree.
+    println!("cargo:rerun-if-env-changed=PROTOC");
+    println!("cargo:rerun-if-env-changed=PROTOC_INCLUDE");
+    let use_vendored_protoc = std::env::var_os("PROTOC").is_none();
+
+    // In vendored mode, preserve the vendored include-tree guarantee even when
+    // the caller has PROTOC_INCLUDE set: prost validates that ambient path
+    // independently of explicit includes. Re-enter with a child-only
+    // environment override.
+    if use_vendored_protoc && std::env::var_os("PROTOC_INCLUDE").is_some() {
         let status = std::process::Command::new(std::env::current_exe()?)
             .env_remove("PROTOC_INCLUDE")
             .status()?;
@@ -18,10 +26,17 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     println!("cargo:rerun-if-changed=proto/openshell_sandbox.proto");
 
     // Configure the vendored compiler and well-known includes without changing
-    // the build process environment.
+    // the build process environment. With a caller-supplied PROTOC, leave both
+    // to prost.
     let mut proto_config = tonic_prost_build::Config::new();
-    proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
-    let proto_include = protoc_bin_vendored::include_path()?;
+    let proto_include = if use_vendored_protoc {
+        proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
+        Some(protoc_bin_vendored::include_path()?)
+    } else {
+        None
+    };
+    let mut include_dirs = vec![std::path::PathBuf::from("proto")];
+    include_dirs.extend(proto_include);
 
     tonic_prost_build::configure()
         .build_server(true)
@@ -29,7 +44,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         .compile_with_config(
             proto_config,
             &[std::path::PathBuf::from("proto/openshell_sandbox.proto")],
-            &[std::path::PathBuf::from("proto"), proto_include],
+            &include_dirs,
         )?;
     Ok(())
 }

crates/openshell-server/build.rs

@@ -5,10 +5,18 @@ use std::env;
 use std::path::PathBuf;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    // Preserve the vendored include-tree guarantee even when the caller has
-    // PROTOC_INCLUDE set: prost validates that ambient path independently of
-    // explicit includes. Re-enter with a child-only environment override.
-    if env::var_os("PROTOC_INCLUDE").is_some() {
+    // A caller-supplied PROTOC (for example a distro package's system
+    // compiler) is used as-is and prost resolves its own includes. Without it,
+    // use the vendored compiler and include tree.
+    println!("cargo:rerun-if-env-changed=PROTOC");
+    println!("cargo:rerun-if-env-changed=PROTOC_INCLUDE");
+    let use_vendored_protoc = env::var_os("PROTOC").is_none();
+
+    // In vendored mode, preserve the vendored include-tree guarantee even when
+    // the caller has PROTOC_INCLUDE set: prost validates that ambient path
+    // independently of explicit includes. Re-enter with a child-only
+    // environment override.
+    if use_vendored_protoc && env::var_os("PROTOC_INCLUDE").is_some() {
         let status = std::process::Command::new(env::current_exe()?)
             .env_remove("PROTOC_INCLUDE")
             .status()?;
@@ -37,12 +45,19 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     // Configure the vendored compiler and well-known includes without changing
-    // the build process environment.
+    // the build process environment. With a caller-supplied PROTOC, leave both
+    // to prost.
     let mut proto_config = tonic_prost_build::Config::new();
-    proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
-    let proto_include = protoc_bin_vendored::include_path()?;
+    let proto_include = if use_vendored_protoc {
+        proto_config.protoc_executable(protoc_bin_vendored::protoc_bin_path()?);
+        Some(protoc_bin_vendored::include_path()?)
+    } else {
+        None
+    };
 
     let descriptor_path = PathBuf::from(env::var("OUT_DIR")?).join("storage_descriptor.bin");
+    let mut include_dirs = vec![storage_proto_dir, public_proto_dir];
+    include_dirs.extend(proto_include);
     tonic_prost_build::configure()
         .build_server(false)
         .build_client(false)
@@ -56,11 +71,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
             "::openshell_core::proto::sandbox::v1",
         )
         .file_descriptor_set_path(&descriptor_path)
-        .compile_with_config(
-            proto_config,
-            &[storage_proto],
-            &[storage_proto_dir, public_proto_dir, proto_include],
-        )?;
+        .compile_with_config(proto_config, &[storage_proto], &include_dirs)?;
 
     Ok(())
 }