feat: support async_trait-less generation

Cargo.toml

@@ -5,11 +5,12 @@ members = [
   "tonic-health",
   "tonic-types",
   "tonic-reflection",
-  "tonic-web", # Non-published crates
+  "tonic-web",                        # Non-published crates
   "examples",
   "codegen",
-  "interop", # Tests
+  "interop",                          # Tests
   "tests/disable_comments",
+  "tests/emit_async_trait",
   "tests/included_service",
   "tests/same_name",
   "tests/service_named_service",

codegen/Cargo.toml

@@ -8,4 +8,8 @@ version = "0.1.0"
 
 [dependencies]
 tempfile = "3.8.0"
-tonic-build = {path = "../tonic-build", default-features = false, features = ["prost", "cleanup-markdown"]}
+tonic-build = { path = "../tonic-build", default-features = false, features = [
+    "prost",
+    "async_trait",
+    "cleanup-markdown",
+] }

tests/emit_async_trait/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+edition = "2021"
+license = "MIT"
+name = "emit_async_trait"
+publish = false
+version = "0.1.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+default = ["async_trait"]
+async_trait = ["tonic-build/async_trait"]
+
+[dependencies]
+tokio = { version = "1.0", features = ["macros", "rt-multi-thread", "net"] }
+tokio-stream = { version = "0.1", features = ["net"] }
+prost = "0.12"
+tonic = { path = "../../tonic" }
+
+[build-dependencies]
+tonic-build = { path = "../../tonic-build", default-features = false, features = [
+    "transport",
+    "prost",
+] }
+
+[package.metadata.cargo-machete]
+ignored = ["prost"]

tests/emit_async_trait/build.rs

@@ -0,0 +1,5 @@
+fn main() {
+    tonic_build::configure()
+        .compile(&["proto/test.proto"], &["proto"])
+        .unwrap();
+}

tests/emit_async_trait/proto/test.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package test;
+
+import "google/protobuf/empty.proto";
+
+service Test {
+  rpc Unary(google.protobuf.Empty) returns (google.protobuf.Empty);
+  rpc ServerStream(google.protobuf.Empty) returns (stream google.protobuf.Empty);
+  rpc ClientStream(stream google.protobuf.Empty) returns (google.protobuf.Empty);
+  rpc BidirectionalStream(stream google.protobuf.Empty) returns (stream google.protobuf.Empty);
+}

tests/emit_async_trait/src/lib.rs

@@ -0,0 +1,39 @@
+#![allow(unused_imports)]
+
+use std::pin::Pin;
+use tokio_stream::{Stream, StreamExt};
+use tonic::{Request, Response, Status, Streaming};
+
+tonic::include_proto!("test");
+
+#[derive(Debug, Default)]
+struct Svc;
+
+#[cfg_attr(feature = "async_trait", tonic::async_trait)]
+impl test_server::Test for Svc {
+    type ServerStreamStream = Pin<Box<dyn Stream<Item = Result<(), Status>> + Send + 'static>>;
+    type BidirectionalStreamStream =
+        Pin<Box<dyn Stream<Item = Result<(), Status>> + Send + 'static>>;
+
+    async fn unary(&self, _: Request<()>) -> Result<Response<()>, Status> {
+        Err(Status::permission_denied(""))
+    }
+
+    async fn server_stream(
+        &self,
+        _: Request<()>,
+    ) -> Result<Response<Self::ServerStreamStream>, Status> {
+        Err(Status::permission_denied(""))
+    }
+
+    async fn client_stream(&self, _: Request<Streaming<()>>) -> Result<Response<()>, Status> {
+        Err(Status::permission_denied(""))
+    }
+
+    async fn bidirectional_stream(
+        &self,
+        _: Request<Streaming<()>>,
+    ) -> Result<Response<Self::BidirectionalStreamStream>, Status> {
+        Err(Status::permission_denied(""))
+    }
+}

tonic-build/Cargo.toml

@@ -22,10 +22,11 @@ quote = "1.0"
 syn = "2.0"
 
 [features]
-default = ["transport", "prost"]
+default = ["transport", "prost", "async_trait"]
 prost = ["prost-build"]
 cleanup-markdown = ["prost", "prost-build/cleanup-markdown"]
 transport = []
+async_trait = []
 
 [package.metadata.docs.rs]
 all-features = true