Introduce alloc feature for optional allocation

Wrap heap-allocated types and service generation in the `alloc` feature
flag to support environments without a memory allocator.

Cargo.lock

@@ -562,6 +562,7 @@ checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 name = "hello-world"
 version = "0.1.0"
 dependencies = [
+ "async-trait",
  "bytes",
  "futures-util",
  "http",

codegen/src/generator.rs

@@ -1,13 +1,26 @@
 use crate::google::protobuf::descriptor::{
     DescriptorProto, EnumDescriptorProto, FieldDescriptorProto, FileDescriptorProto,
-    FileDescriptorSet, MessageOptions, MethodDescriptorProto, OneofDescriptorProto, ServiceDescriptorProto,
+    FileDescriptorSet, MessageOptions, MethodDescriptorProto, OneofDescriptorProto,
+    ServiceDescriptorProto,
 };
 use roto_runtime::ProtoAccessor;
 use std::collections::{HashMap, HashSet};
 use std::str;
 
 const DATA_IMPORTS: &str = "use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};\nuse core::str;\n#[cfg(feature = \"alloc\")]\nuse bytes::{Bytes, BytesMut, Buf, BufMut};\n";
-const SERVICE_IMPORTS: &str = "use tonic::{Request, Response, Status};\nuse tokio_stream::Stream;\nuse std::pin::Pin;\nuse std::sync::Arc;\nuse std::task::{Context, Poll};\nuse std::future::Future;\nuse tonic::body::BoxBody;\nuse tower::Service;\nuse futures_util::StreamExt;\nuse http_body_util::BodyExt;\nuse http_body::Body;\nuse crate::{BufferPool, StatusBody};\n";
+const SERVICE_IMPORTS: &str =
+    "#[cfg(feature = \"alloc\")]\nuse tonic::{Request, Response, Status};\n\
+     #[cfg(feature = \"alloc\")]\nuse tokio_stream::Stream;\n\
+     #[cfg(feature = \"alloc\")]\nuse std::pin::Pin;\n\
+     #[cfg(feature = \"alloc\")]\nuse std::sync::Arc;\n\
+     #[cfg(feature = \"alloc\")]\nuse std::task::{Context, Poll};\n\
+     #[cfg(feature = \"alloc\")]\nuse std::future::Future;\n\
+     #[cfg(feature = \"alloc\")]\nuse tonic::body::BoxBody;\n\
+     #[cfg(feature = \"alloc\")]\nuse tower::Service;\n\
+     #[cfg(feature = \"alloc\")]\nuse futures_util::StreamExt;\n\
+     #[cfg(feature = \"alloc\")]\nuse http_body_util::BodyExt;\n\
+     #[cfg(feature = \"alloc\")]\nuse http_body::Body;\n\
+     #[cfg(feature = \"alloc\")]\nuse crate::{BufferPool, StatusBody};\n";
 
 pub fn to_pascal_case(s: &str) -> String {
     s.split('_')
@@ -36,7 +49,11 @@ pub fn to_snake_case(s: &str) -> String {
     result
 }
 
-fn map_type_to_rust_accessor(field_type: i32, label: i32, is_map: bool) -> (String, String, String) {
+fn map_type_to_rust_accessor(
+    field_type: i32,
+    label: i32,
+    is_map: bool,
+) -> (String, String, String) {
     if label == 3 {
         // LABEL_REPEATED
         let iterator_type = if is_map {
@@ -314,7 +331,7 @@ fn write_message(msg_proto: &DescriptorProto, output: &mut String) {
 
             output.push_str(&format!(
                 "    pub fn {}_or_default(&self) -> roto_runtime::Result<{}> {{\n",
-                 safe_name, rust_type
+                safe_name, rust_type
             ));
             output.push_str(&format!(
                 "        self.{}().or(Ok({}))\n",
@@ -440,18 +457,30 @@ fn write_message(msg_proto: &DescriptorProto, output: &mut String) {
 
     output.push_str(&format!("    pub fn finish(self) -> roto_runtime::Result<&'b mut [u8]> {{\n        self.builder.finish()\n    }}\n}}\n\n"));
 
-    output.push_str(&format!("#[cfg(feature = \"alloc\")]\npub struct Owned{} {{\n", msg_name));
+    output.push_str(&format!(
+        "#[cfg(feature = \"alloc\")]\npub struct Owned{} {{\n",
+        msg_name
+    ));
     output.push_str("    pub data: bytes::Bytes,\n");
     output.push_str("}\n\n");
 
-    output.push_str(&format!("#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoOwned for Owned{} {{\n", msg_name));
+    output.push_str(&format!(
+        "#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoOwned for Owned{} {{\n",
+        msg_name
+    ));
     output.push_str(&format!("    type Reader<'a> = {}<'a>;\n", msg_name));
     output.push_str(&format!("    fn reader(&self) -> {}<'_> {{\n", msg_name));
-    output.push_str(&format!("        {}::new(&self.data).expect(\"failed to create reader\")\n", msg_name));
+    output.push_str(&format!(
+        "        {}::new(&self.data).expect(\"failed to create reader\")\n",
+        msg_name
+    ));
     output.push_str("    }\n");
     output.push_str("}\n\n");
 
-    output.push_str(&format!("#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoMessage for Owned{} {{\n", msg_name));
+    output.push_str(&format!(
+        "#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoMessage for Owned{} {{\n",
+        msg_name
+    ));
     output.push_str("    fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {\n");
     output.push_str(&format!("        Ok(Owned{} {{ data: buf }})\n", msg_name));
     output.push_str("    }\n\n");
@@ -551,7 +580,14 @@ where
             }
         }
 
-        let rust_file_name = format!("{}.rs", std::path::Path::new(proto_name).file_stem().unwrap().to_str().unwrap());
+        let rust_file_name = format!(
+            "{}.rs",
+            std::path::Path::new(proto_name)
+                .file_stem()
+                .unwrap()
+                .to_str()
+                .unwrap()
+        );
 
         let mut output = String::new();
         output.push_str("// @generated by protoc-gen-roto — do not edit\n");
@@ -639,7 +675,8 @@ pub fn generate_protobuf_code(
             for enum_res in file_proto.enum_type() {
                 let (enum_data, _) = enum_res.expect("Failed to iterate enum");
                 write_enum(
-                    &EnumDescriptorProto::new(enum_data).expect("Failed to parse EnumDescriptorProto"),
+                    &EnumDescriptorProto::new(enum_data)
+                        .expect("Failed to parse EnumDescriptorProto"),
                     output,
                 );
             }
@@ -672,7 +709,8 @@ pub fn generate_service_code(
             for svc_res in file_proto.service() {
                 let (svc_data, _) = svc_res.expect("Failed to iterate service");
                 write_service(
-                    &ServiceDescriptorProto::new(svc_data).expect("Failed to parse ServiceDescriptorProto"),
+                    &ServiceDescriptorProto::new(svc_data)
+                        .expect("Failed to parse ServiceDescriptorProto"),
                     &package,
                     output,
                 );
@@ -709,13 +747,7 @@ pub fn generate_rust_code(
     result.sort_by(|a, b| a.0.cmp(&b.0));
 
     if generate_mod_files {
-        let mods = generate_files_common(
+        let mods = generate_files_common(set, files_to_generate, true, "", |_, _| {});
-            set,
-            files_to_generate,
-            true,
-            "",
-            |_, _| {},
-        );
         for (filename, content) in mods {
             if filename == "mod.rs" || filename.contains("/mod.rs") {
                 result.push((filename, content));
@@ -732,12 +764,18 @@ fn strip_boilerplate(content: &str) -> String {
 
 fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut String) {
     output.push_str(SERVICE_IMPORTS);
+    output.push_str("\n");
     let svc_name = to_pascal_case(svc_proto.name().unwrap());
-    output.push_str(&format!("#[async_trait::async_trait]\npub trait {}: Send + Sync + 'static {{\n", svc_name));
+    output.push_str("#[cfg(feature = \"alloc\")]\n");
+    output.push_str(&format!(
+        "#[async_trait::async_trait]\npub trait {}: Send + Sync + 'static {{\n",
+        svc_name
+    ));
 
     for method_res in svc_proto.method() {
         let (method_data, _) = method_res.expect("Failed to iterate method");
-        let method_proto = MethodDescriptorProto::new(method_data).expect("Failed to parse MethodDescriptorProto");
+        let method_proto =
+            MethodDescriptorProto::new(method_data).expect("Failed to parse MethodDescriptorProto");
         let method_name = to_snake_case(method_proto.name().unwrap());
 
         let input_full_name = method_proto.input_type().unwrap();
@@ -759,7 +797,10 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
         };
 
         let resp_type = if server_streaming {
-            format!("Response<Pin<Box<dyn Stream<Item = std::result::Result<{}, Status>> + Send>>>", output_owned)
+            format!(
+                "Response<Pin<Box<dyn Stream<Item = std::result::Result<{}, Status>> + Send>>>",
+                output_owned
+            )
         } else {
             format!("Response<{}>", output_owned)
         };
@@ -772,27 +813,46 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
     output.push_str("}\n\n");
 
     let server_name = format!("{}Server", svc_name);
-    output.push_str(&format!("#[derive(Clone)]\npub struct {} {{\n", server_name));
+    output.push_str("#[cfg(feature = \"alloc\")]\n");
+    output.push_str(&format!(
+        "#[derive(Clone)]\npub struct {} {{\n",
+        server_name
+    ));
     output.push_str(&format!("    inner: Arc<dyn {}>,\n", svc_name));
     output.push_str("    pool: Arc<BufferPool>,\n");
     output.push_str("}\n\n");
 
+    output.push_str("#[cfg(feature = \"alloc\")]\n");
     output.push_str(&format!("impl {} {{\n", server_name));
-    output.push_str(&format!("    pub fn new(inner: Arc<dyn {}>, pool: Arc<BufferPool>) -> Self {{\n", svc_name));
+    output.push_str(&format!(
+        "    pub fn new(inner: Arc<dyn {}>, pool: Arc<BufferPool>) -> Self {{\n",
+        svc_name
+    ));
     output.push_str("        Self { inner, pool }\n");
     output.push_str("    }\n");
     output.push_str("}\n\n");
 
-    output.push_str(&format!("impl tonic::server::NamedService for {} {{\n", server_name));
+    output.push_str("#[cfg(feature = \"alloc\")]\n");
+    output.push_str(&format!(
+        "impl tonic::server::NamedService for {} {{\n",
+        server_name
+    ));
     let full_svc_name = if package.is_empty() {
         svc_proto.name().unwrap().to_string()
     } else {
         format!("{}.{}", package, svc_proto.name().unwrap())
     };
-    output.push_str(&format!("    const NAME: &'static str = \"{}\";\n", full_svc_name));
+    output.push_str(&format!(
+        "    const NAME: &'static str = \"{}\";\n",
+        full_svc_name
+    ));
     output.push_str("}\n\n");
 
-    output.push_str(&format!("impl Service<http::Request<BoxBody>> for {} {{\n", server_name));
+    output.push_str("#[cfg(feature = \"alloc\")]\n");
+    output.push_str(&format!(
+        "impl Service<http::Request<BoxBody>> for {} {{\n",
+        server_name
+    ));
     output.push_str("    type Response = http::Response<BoxBody>;\n");
     output.push_str("    type Error = std::convert::Infallible;\n");
     output.push_str("    type Future = Pin<Box<dyn Future<Output = std::result::Result<Self::Response, Self::Error>> + Send>>;\n\n");
@@ -829,14 +889,20 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
     let mut methods = Vec::new();
     for method_res in svc_proto.method() {
         let (method_data, _) = method_res.expect("Failed to iterate method");
-        let method_proto = MethodDescriptorProto::new(method_data).expect("Failed to parse MethodDescriptorProto");
+        let method_proto =
+            MethodDescriptorProto::new(method_data).expect("Failed to parse MethodDescriptorProto");
         let original_method_name = method_proto.name().unwrap().to_string();
         let method_name = to_snake_case(&original_method_name);
         let input_full_name = method_proto.input_type().unwrap();
         let input_type = input_full_name.split('.').last().unwrap();
         let input_owned = format!("Owned{}", input_type);
         let server_streaming = method_proto.server_streaming().unwrap_or(false);
-        methods.push((original_method_name, method_name, input_owned, server_streaming));
+        methods.push((
+            original_method_name,
+            method_name,
+            input_owned,
+            server_streaming,
+        ));
     }
 
     for (original_method_name, method_name, input_owned, server_streaming) in methods {
@@ -846,7 +912,12 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
             let full_path = if package.is_empty() {
                 format!("/{}/{}", svc_proto.name().unwrap(), original_method_name)
             } else {
-                format!("/{}.{}/{}", package, svc_proto.name().unwrap(), original_method_name)
+                format!(
+                    "/{}.{}/{}",
+                    package,
+                    svc_proto.name().unwrap(),
+                    original_method_name
+                )
             };
             output.push_str(&format!("            if path == \"{}\" {{\n", full_path));
             output.push_str("                let res_body = BoxBody::new(StatusBody::new(Some(Bytes::from_static(&[0, 0, 0, 0, 0])), 0));\n");
@@ -857,17 +928,28 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
         let full_path = if package.is_empty() {
             format!("/{}/{}", svc_proto.name().unwrap(), original_method_name)
         } else {
-            format!("/{}.{}/{}", package, svc_proto.name().unwrap(), original_method_name)
+            format!(
+                "/{}.{}/{}",
+                package,
+                svc_proto.name().unwrap(),
+                original_method_name
+            )
         };
         output.push_str(&format!("            if path == \"{}\" {{\n", full_path));
-        output.push_str(&format!("                let request_msg = match {}::decode(payload) {{\n", input_owned));
+        output.push_str(&format!(
+            "                let request_msg = match {}::decode(payload) {{\n",
+            input_owned
+        ));
         output.push_str("                    Ok(msg) => msg,\n");
         output.push_str("                    Err(e) => {\n");
         output.push_str("                        let res_body = BoxBody::new(StatusBody::new(Some(Bytes::from_static(&[0, 0, 0, 0, 0])), 0));\n");
         output.push_str("                        return Ok(http::Response::builder().status(200).body(res_body).unwrap());\n");
         output.push_str("                    }\n");
         output.push_str("                };\n\n");
-        output.push_str(&format!("                let response = match inner.{}(Request::new(request_msg)).await {{\n", method_name));
+        output.push_str(&format!(
+            "                let response = match inner.{}(Request::new(request_msg)).await {{\n",
+            method_name
+        ));
         output.push_str("                    Ok(res) => res,\n");
         output.push_str("                    Err(e) => {\n");
         output.push_str("                        let res_body = BoxBody::new(StatusBody::new(Some(Bytes::from_static(&[0, 0, 0, 0, 0])), 0));\n");
@@ -884,7 +966,9 @@ fn write_service(svc_proto: &ServiceDescriptorProto, package: &str, output: &mut
         output.push_str("                let frame_len = res_buf.len();\n");
         output.push_str("                let frame = res_buf.split_to(frame_len).freeze();\n");
         output.push_str("                pool.put(res_buf);\n");
-        output.push_str("                let res_body = BoxBody::new(StatusBody::new(Some(frame), 0));\n");
+        output.push_str(
+            "                let res_body = BoxBody::new(StatusBody::new(Some(frame), 0));\n",
+        );
         output.push_str("                routed = true;\n");
         output.push_str("                return Ok(http::Response::builder().status(200).header(\"content-type\", \"application/grpc\").body(res_body).unwrap());\n");
         output.push_str("            }\n");

examples/hello_world/Cargo.toml

@@ -24,7 +24,12 @@ futures-util = "0.3"
 http-body-util = "0.1"
 http = "1.1"
 http-body = "1.0"
+async-trait = "0.1"
 
 [build-dependencies]
 tonic-build = "0.12"
 roto-codegen = { path = "../../codegen" }
+
+[features]
+default = ["alloc"]
+alloc = []

examples/no_std_test/src/main.rs

@@ -1,5 +1,5 @@
 #![no_std]
-#![no_main]
+#![cfg_attr(not(test), no_main)]
 
 mod helloworld;
 
@@ -8,10 +8,11 @@ extern crate alloc;
 
 use roto_runtime::{ProtoAccessor, RotoMessage, RotoOwned};
 
-#[cfg(feature = "alloc")]
+#[cfg(all(feature = "alloc", not(test)))]
 #[global_allocator]
 static ALLOCATOR: embedded_alloc::Heap = embedded_alloc::Heap::empty();
 
+#[cfg(not(test))]
 #[panic_handler]
 fn panic(_info: &core::panic::PanicInfo) -> ! {
     loop {}
@@ -27,6 +28,7 @@ pub extern "C" fn _critical_section_1_0_release() {}
 
 static HELLO_DATA: &[u8] = &[0x0A, 0x05, 0x57, 0x6f, 0x72, 0x6c, 0x64];
 
+#[cfg(all(not(test), not(feature = "alloc")))]
 #[unsafe(no_mangle)]
 pub extern "C" fn _start() -> ! {
     #[cfg(not(feature = "alloc"))]
@@ -58,3 +60,15 @@ pub extern "C" fn _start() -> ! {
 
     loop {}
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_helloworld_decoding() {
+        let hello = helloworld::Hello::new(HELLO_DATA).expect("failed to decode hello");
+        let name = hello.name().expect("failed to get name");
+        assert!(!name.is_empty());
+    }
+}

roto-tonic/Cargo.toml

@@ -19,3 +19,7 @@ http = "1.1"
 
 [build-dependencies]
 tonic-build = "0.12"
+
+[features]
+default = ["alloc"]
+alloc = []

roto-tonic/src/generated/interop.rs

@@ -2,19 +2,9 @@
 #[allow(unused_imports)]
 
 use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};
-use std::str;
+use core::str;
+#[cfg(feature = "alloc")]
 use bytes::{Bytes, BytesMut, Buf, BufMut};
-use tonic::{Request, Response, Status};
-use std::sync::Arc;
-use std::pin::Pin;
-use std::task::{Context, Poll};
-use std::future::Future;
-use tower::Service;
-use tonic::body::BoxBody;
-use tokio_stream::Stream;
-use crate::{BufferPool, StatusBody};
-use async_trait::async_trait;
-use http_body_util::BodyExt;
 
 pub struct UnaryRequest<'a> {
     accessor: roto_runtime::ProtoAccessor<'a>,
@@ -39,7 +29,7 @@ message_offset,
     pub fn message(&self) -> roto_runtime::Result<&'a str> {
         let offset = self.message_offset.ok_or(roto_runtime::RotoError::FieldNotFound)?;
         let (bytes, _) = self.accessor.get_value_at(offset)?;
-        std::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
+        core::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
     }
 
     pub fn message_or_default(&self) -> roto_runtime::Result<&'a str> {
@@ -92,10 +82,12 @@ impl<'b> UnaryRequestBuilder<'b> {
     }
 }
 
+#[cfg(feature = "alloc")]
 pub struct OwnedUnaryRequest {
     pub data: bytes::Bytes,
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoOwned for OwnedUnaryRequest {
     type Reader<'a> = UnaryRequest<'a>;
     fn reader(&self) -> UnaryRequest<'_> {
@@ -103,6 +95,7 @@ impl roto_runtime::RotoOwned for OwnedUnaryRequest {
     }
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoMessage for OwnedUnaryRequest {
     fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {
         Ok(OwnedUnaryRequest { data: buf })
@@ -136,7 +129,7 @@ reply_offset,
     pub fn reply(&self) -> roto_runtime::Result<&'a str> {
         let offset = self.reply_offset.ok_or(roto_runtime::RotoError::FieldNotFound)?;
         let (bytes, _) = self.accessor.get_value_at(offset)?;
-        std::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
+        core::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
     }
 
     pub fn reply_or_default(&self) -> roto_runtime::Result<&'a str> {
@@ -189,10 +182,12 @@ impl<'b> UnaryResponseBuilder<'b> {
     }
 }
 
+#[cfg(feature = "alloc")]
 pub struct OwnedUnaryResponse {
     pub data: bytes::Bytes,
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoOwned for OwnedUnaryResponse {
     type Reader<'a> = UnaryResponse<'a>;
     fn reader(&self) -> UnaryResponse<'_> {
@@ -200,6 +195,7 @@ impl roto_runtime::RotoOwned for OwnedUnaryResponse {
     }
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoMessage for OwnedUnaryResponse {
     fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {
         Ok(OwnedUnaryResponse { data: buf })
@@ -233,7 +229,7 @@ query_offset,
     pub fn query(&self) -> roto_runtime::Result<&'a str> {
         let offset = self.query_offset.ok_or(roto_runtime::RotoError::FieldNotFound)?;
         let (bytes, _) = self.accessor.get_value_at(offset)?;
-        std::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
+        core::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
     }
 
     pub fn query_or_default(&self) -> roto_runtime::Result<&'a str> {
@@ -286,10 +282,12 @@ impl<'b> StreamingRequestBuilder<'b> {
     }
 }
 
+#[cfg(feature = "alloc")]
 pub struct OwnedStreamingRequest {
     pub data: bytes::Bytes,
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoOwned for OwnedStreamingRequest {
     type Reader<'a> = StreamingRequest<'a>;
     fn reader(&self) -> StreamingRequest<'_> {
@@ -297,6 +295,7 @@ impl roto_runtime::RotoOwned for OwnedStreamingRequest {
     }
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoMessage for OwnedStreamingRequest {
     fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {
         Ok(OwnedStreamingRequest { data: buf })
@@ -330,7 +329,7 @@ item_offset,
     pub fn item(&self) -> roto_runtime::Result<&'a str> {
         let offset = self.item_offset.ok_or(roto_runtime::RotoError::FieldNotFound)?;
         let (bytes, _) = self.accessor.get_value_at(offset)?;
-        std::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
+        core::str::from_utf8(bytes).map_err(|_| roto_runtime::RotoError::WireFormatViolation)
     }
 
     pub fn item_or_default(&self) -> roto_runtime::Result<&'a str> {
@@ -383,10 +382,12 @@ impl<'b> StreamingResponseBuilder<'b> {
     }
 }
 
+#[cfg(feature = "alloc")]
 pub struct OwnedStreamingResponse {
     pub data: bytes::Bytes,
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoOwned for OwnedStreamingResponse {
     type Reader<'a> = StreamingResponse<'a>;
     fn reader(&self) -> StreamingResponse<'_> {
@@ -394,6 +395,7 @@ impl roto_runtime::RotoOwned for OwnedStreamingResponse {
     }
 }
 
+#[cfg(feature = "alloc")]
 impl roto_runtime::RotoMessage for OwnedStreamingResponse {
     fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {
         Ok(OwnedStreamingResponse { data: buf })
@@ -405,28 +407,62 @@ impl roto_runtime::RotoMessage for OwnedStreamingResponse {
 }
 
 
-#[async_trait]
+// @generated by protoc-gen-roto — do not edit
+#[allow(unused_imports)]
+
+
+#[cfg(feature = "alloc")]
+use tonic::{Request, Response, Status};
+#[cfg(feature = "alloc")]
+use tokio_stream::Stream;
+#[cfg(feature = "alloc")]
+use std::pin::Pin;
+#[cfg(feature = "alloc")]
+use std::sync::Arc;
+#[cfg(feature = "alloc")]
+use std::task::{Context, Poll};
+#[cfg(feature = "alloc")]
+use std::future::Future;
+#[cfg(feature = "alloc")]
+use tonic::body::BoxBody;
+#[cfg(feature = "alloc")]
+use tower::Service;
+#[cfg(feature = "alloc")]
+use futures_util::StreamExt;
+#[cfg(feature = "alloc")]
+use http_body_util::BodyExt;
+#[cfg(feature = "alloc")]
+use http_body::Body;
+#[cfg(feature = "alloc")]
+use crate::{BufferPool, StatusBody};
+
+#[cfg(feature = "alloc")]
+#[async_trait::async_trait]
 pub trait InteropService: Send + Sync + 'static {
     async fn unary_call(&self, request: Request<OwnedUnaryRequest>) -> std::result::Result<Response<OwnedUnaryResponse>, Status>;
     async fn streaming_call(&self, request: Request<OwnedStreamingRequest>) -> std::result::Result<Response<Pin<Box<dyn Stream<Item = std::result::Result<OwnedStreamingResponse, Status>> + Send>>>, Status>;
 }
 
+#[cfg(feature = "alloc")]
 #[derive(Clone)]
 pub struct InteropServiceServer {
     inner: Arc<dyn InteropService>,
     pool: Arc<BufferPool>,
 }
 
+#[cfg(feature = "alloc")]
 impl InteropServiceServer {
     pub fn new(inner: Arc<dyn InteropService>, pool: Arc<BufferPool>) -> Self {
         Self { inner, pool }
     }
 }
 
+#[cfg(feature = "alloc")]
 impl tonic::server::NamedService for InteropServiceServer {
     const NAME: &'static str = "interop.InteropService";
 }
 
+#[cfg(feature = "alloc")]
 impl Service<http::Request<BoxBody>> for InteropServiceServer {
     type Response = http::Response<BoxBody>;
     type Error = std::convert::Infallible;

runtime/src/lib.rs

@@ -1,5 +1,8 @@
 #![no_std]
 
+#[cfg(feature = "alloc")]
+extern crate alloc;
+
 #[cfg(feature = "std")]
 extern crate std;
 
@@ -438,6 +441,8 @@ impl<'a> Iterator for RawFieldIterator<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(feature = "alloc")]
+    use alloc::{vec, vec::{Vec}};
 
     #[test]
     fn test_varint_read_write() {