feat(build): support adding attributes to clients and servers (#684)

examples/build.rs

@@ -15,6 +15,14 @@ fn main() {
 
     tonic_build::compile_protos("proto/echo/echo.proto").unwrap();
 
+    tonic_build::configure()
+        .server_mod_attribute("attrs", "#[cfg(feature = \"server\")]")
+        .server_attribute("Echo", "#[derive(PartialEq)]")
+        .client_mod_attribute("attrs", "#[cfg(feature = \"client\")]")
+        .client_attribute("Echo", "#[derive(PartialEq)]")
+        .compile(&["proto/attrs/attrs.proto"], &["proto"])
+        .unwrap();
+
     tonic_build::configure()
         .build_server(false)
         .compile(

examples/proto/attrs/attrs.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package attrs;
+
+// EchoRequest is the request for echo.
+message EchoRequest {
+  string message = 1;
+}
+
+// EchoResponse is the response for echo.
+message EchoResponse {
+  string message = 1;
+}
+
+// Echo is the echo service.
+service Echo {
+  // UnaryEcho is unary echo.
+  rpc UnaryEcho(EchoRequest) returns (EchoResponse) {}
+}