swarm-derive: Allow for templated behaviours

swarm-derive/CHANGELOG.md

@@ -1,3 +1,10 @@
+# 0.30.1
+
+- Fix an issue where the derive would generate bad code if the type parameters between the behaviour and a custom
+  out event differed. See [PR XXXX].
+
+[PR XXXX]: https://github.com/libp2p/rust-libp2p/pull/XXXX
+
 # 0.30.0
 
 - Remove support for removed `NetworkBehaviourEventProcess`. See [PR 2840].

swarm-derive/Cargo.toml

@@ -22,3 +22,4 @@ syn = { version = "1.0.8", default-features = false, features = ["clone-impls",
 libp2p = { path = "../", default-features = false, features = ["ping", "identify", "kad"] }
 either = "1.6.0"
 futures = "0.3.1"
+void = "1"

swarm-derive/src/lib.rs

@@ -100,7 +100,7 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
                     .iter()
                     .map(|field| {
                         let ty = &field.ty;
-                        quote! {#name #ty_generics: From< <#ty as #trait_to_impl>::OutEvent >}
+                        quote! {#name: From< <#ty as #trait_to_impl>::OutEvent >}
                     })
                     .collect::<Vec<_>>();
                 (name, definition, from_clauses)
@@ -537,6 +537,12 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
         })
     });
 
+    let out_event_reference = if out_event_definition.is_some() {
+        quote! { #out_event_name #ty_generics }
+    } else {
+        quote! { #out_event_name }
+    };
+
     // Now the magic happens.
     let final_quote = quote! {
         #out_event_definition
@@ -545,7 +551,7 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
         #where_clause
         {
             type ConnectionHandler = #connection_handler_ty;
-            type OutEvent = #out_event_name #ty_generics;
+            type OutEvent = #out_event_reference;
 
             fn new_handler(&mut self) -> Self::ConnectionHandler {
                 use #into_connection_handler;

swarm-derive/tests/test.rs

@@ -350,3 +350,65 @@ fn generated_out_event_derive_debug() {
 
     require_debug::<Foo>();
 }
+
+#[test]
+fn custom_out_event_no_type_parameters() {
+    use libp2p::core::connection::ConnectionId;
+    use libp2p::swarm::handler::DummyConnectionHandler;
+    use libp2p::swarm::{
+        ConnectionHandler, IntoConnectionHandler, NetworkBehaviourAction, PollParameters,
+    };
+    use libp2p::PeerId;
+    use std::task::Context;
+    use std::task::Poll;
+
+    pub struct TemplatedBehaviour<T: 'static> {
+        _data: T,
+    }
+
+    impl<T> NetworkBehaviour for TemplatedBehaviour<T> {
+        type ConnectionHandler = DummyConnectionHandler;
+        type OutEvent = void::Void;
+
+        fn new_handler(&mut self) -> Self::ConnectionHandler {
+            DummyConnectionHandler::default()
+        }
+
+        fn inject_event(
+            &mut self,
+            _peer: PeerId,
+            _connection: ConnectionId,
+            message: <<Self::ConnectionHandler as IntoConnectionHandler>::Handler as ConnectionHandler>::OutEvent,
+        ) {
+            void::unreachable(message);
+        }
+
+        fn poll(
+            &mut self,
+            _ctx: &mut Context,
+            _: &mut impl PollParameters,
+        ) -> Poll<NetworkBehaviourAction<Self::OutEvent, Self::ConnectionHandler>> {
+            Poll::Pending
+        }
+    }
+
+    #[derive(NetworkBehaviour)]
+    #[behaviour(out_event = "OutEvent")]
+    struct Behaviour<T: 'static + Send> {
+        custom: TemplatedBehaviour<T>,
+    }
+
+    #[derive(Debug)]
+    enum OutEvent {
+        None,
+    }
+
+    impl From<void::Void> for OutEvent {
+        fn from(_e: void::Void) -> Self {
+            Self::None
+        }
+    }
+
+    require_net_behaviour::<Behaviour<String>>();
+    require_net_behaviour::<Behaviour<()>>();
+}