swarm-derive/: Generate OutEvent if not provided

CHANGELOG.md

@@ -47,6 +47,8 @@
 
 - Update to [`libp2p-dcutr` `v0.5.0`](protocols/dcutr/CHANGELOG.md#050).
 
+- Update to [`libp2p-derive` `v0.29.0`](swarm-derive/CHANGELOG.md#0290).
+
 - Update to [`libp2p-rendezvous` `v0.8.0`](protocols/rendezvous/CHANGELOG.md#080).
 
 - Update to [`libp2p-ping` `v0.38.0`](protocols/ping/CHANGELOG.md#0380).

Cargo.toml

@@ -93,7 +93,7 @@ libp2p-relay = { version = "0.11.0", path = "protocols/relay", optional = true }
 libp2p-rendezvous = { version = "0.8.0", path = "protocols/rendezvous", optional = true }
 libp2p-request-response = { version = "0.20.0", path = "protocols/request-response", optional = true }
 libp2p-swarm = { version = "0.38.0", path = "swarm" }
-libp2p-swarm-derive = { version = "0.28.0", path = "swarm-derive" }
+libp2p-swarm-derive = { version = "0.29.0", path = "swarm-derive" }
 libp2p-uds = { version = "0.34.0", path = "transports/uds", optional = true }
 libp2p-wasm-ext = { version = "0.35.0", path = "transports/wasm-ext", default-features = false, optional = true }
 libp2p-yamux = { version = "0.39.0", path = "muxers/yamux", optional = true }

swarm-derive/CHANGELOG.md

@@ -1,3 +1,8 @@
+# 0.29.0 - [unreleased]
+
+- Generate `NetworkBehaviour::OutEvent` if not provided through `#[behaviour(out_event =
+  "MyOutEvent")]` and event processing is disabled (default).
+
 # 0.28.0
 
 - Import `ListenerId` from `libp2p::core::transport`. See [PR 2652].

swarm-derive/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-swarm-derive"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Procedural macros of libp2p-core"
-version = "0.28.0"
+version = "0.29.0"
 authors = ["Parity Technologies <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"
@@ -14,8 +14,9 @@ categories = ["network-programming", "asynchronous"]
 proc-macro = true
 
 [dependencies]
-syn = { version = "1.0.8", default-features = false, features = ["clone-impls", "derive", "parsing", "printing", "proc-macro"] }
+heck = "0.4"
 quote = "1.0"
+syn = { version = "1.0.8", default-features = false, features = ["clone-impls", "derive", "parsing", "printing", "proc-macro"] }
 
 [dev-dependencies]
 libp2p = { path = "../", default-features = false, features = ["ping", "identify", "kad"] }

swarm-derive/src/lib.rs

@@ -20,6 +20,7 @@
 
 #![recursion_limit = "256"]
 
+use heck::ToUpperCamelCase;
 use proc_macro::TokenStream;
 use quote::quote;
 use syn::{parse_macro_input, Data, DataStruct, DeriveInput, Ident};
@@ -99,49 +100,106 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
         .filter(|f| !is_ignored(f))
         .collect::<Vec<_>>();
 
-    // The final out event.
-    // If we find a `#[behaviour(out_event = "Foo")]` attribute on the struct, we set `Foo` as
-    // the out event. Otherwise we use `()`.
-    let out_event = {
-        let mut out = quote! {()};
-        for meta_items in ast.attrs.iter().filter_map(get_meta_items) {
-            for meta_item in meta_items {
-                match meta_item {
-                    syn::NestedMeta::Meta(syn::Meta::NameValue(ref m))
-                        if m.path.is_ident("out_event") =>
-                    {
+    let (out_event_name, out_event_definition, out_event_from_clauses) = {
+        // If we find a `#[behaviour(out_event = "Foo")]` attribute on the
+        // struct, we set `Foo` as the out event. If not, the `OutEvent` is
+        // generated.
+        let user_provided_out_event_name: Option<syn::Type> = ast
+            .attrs
+            .iter()
+            .filter_map(get_meta_items)
+            .flatten()
+            .filter_map(|meta_item| {
+                if let syn::NestedMeta::Meta(syn::Meta::NameValue(ref m)) = meta_item {
+                    if m.path.is_ident("out_event") {
                         if let syn::Lit::Str(ref s) = m.lit {
-                            let ident: syn::Type = syn::parse_str(&s.value()).unwrap();
-                            out = quote! {#ident};
+                            return Some(syn::parse_str(&s.value()).unwrap());
                         }
                     }
-                    _ => (),
                 }
+                None
+            })
+            .next();
+
+        match (user_provided_out_event_name, event_process) {
+            // User provided `OutEvent`.
+            (Some(name), false) => {
+                let definition = None;
+                let from_clauses = data_struct_fields
+                    .iter()
+                    .map(|field| {
+                        let ty = &field.ty;
+                        quote! {#name #ty_generics: From< <#ty as #trait_to_impl>::OutEvent >}
+                    })
+                    .collect::<Vec<_>>();
+                (name, definition, from_clauses)
+            }
+            // User did not provide `OutEvent`. Generate it.
+            (None, false) => {
+                let name: syn::Type = syn::parse_str(&(ast.ident.to_string() + "Event")).unwrap();
+                let definition = {
+                    let fields = data_struct_fields
+                        .iter()
+                        .map(|field| {
+                            let variant: syn::Variant = syn::parse_str(
+                                &field
+                                    .ident
+                                    .clone()
+                                    .expect(
+                                        "Fields of NetworkBehaviour implementation to be named.",
+                                    )
+                                    .to_string()
+                                    .to_upper_camel_case(),
+                            )
+                            .unwrap();
+                            let ty = &field.ty;
+                            quote! {#variant(<#ty as NetworkBehaviour>::OutEvent)}
+                        })
+                        .collect::<Vec<_>>();
+                    let visibility = &ast.vis;
+
+                    Some(quote! {
+                        #visibility enum #name #impl_generics {
+                            #(#fields),*
+                        }
+                    })
+                };
+                let from_clauses = vec![];
+                (name, definition, from_clauses)
+            }
+            // User uses `NetworkBehaviourEventProcess`.
+            (name, true) => {
+                let definition = None;
+                let from_clauses = data_struct_fields
+                    .iter()
+                    .map(|field| {
+                        let ty = &field.ty;
+                        quote! {Self: #net_behv_event_proc<<#ty as #trait_to_impl>::OutEvent>}
+                    })
+                    .collect::<Vec<_>>();
+                (
+                    name.unwrap_or_else(|| syn::parse_str("()").unwrap()),
+                    definition,
+                    from_clauses,
+                )
             }
         }
-        out
     };
 
     // Build the `where ...` clause of the trait implementation.
     let where_clause = {
         let additional = data_struct_fields
             .iter()
-            .flat_map(|field| {
+            .map(|field| {
                 let ty = &field.ty;
-                vec![
-                    quote! {#ty: #trait_to_impl},
-                    if event_process {
-                        quote! {Self: #net_behv_event_proc<<#ty as #trait_to_impl>::OutEvent>}
-                    } else {
-                        quote! {#out_event: From< <#ty as #trait_to_impl>::OutEvent >}
-                    },
-                ]
+                quote! {#ty: #trait_to_impl}
             })
+            .chain(out_event_from_clauses)
             .collect::<Vec<_>>();
 
         if let Some(where_clause) = where_clause {
             if where_clause.predicates.trailing_punct() {
-                Some(quote! {#where_clause #(#additional),*})
+                Some(quote! {#where_clause #(#additional),* })
             } else {
                 Some(quote! {#where_clause, #(#additional),*})
             }
@@ -437,18 +495,18 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
     // List of statements to put in `poll()`.
     //
     // We poll each child one by one and wrap around the output.
-    let poll_stmts = data_struct_fields.iter().enumerate().enumerate().map(|(enum_n, (field_n, field))| {
-        let field_name = match field.ident {
-            Some(ref i) => quote!{ self.#i },
-            None => quote!{ self.#field_n },
-        };
+    let poll_stmts = data_struct_fields.iter().enumerate().map(|(field_n, field)| {
+        let field = field
+            .ident
+            .clone()
+            .expect("Fields of NetworkBehaviour implementation to be named.");
 
-        let mut wrapped_event = if enum_n != 0 {
+        let mut wrapped_event = if field_n != 0 {
             quote!{ #either_ident::Second(event) }
         } else {
             quote!{ event }
         };
-        for _ in 0 .. data_struct_fields.len() - 1 - enum_n {
+        for _ in 0 .. data_struct_fields.len() - 1 - field_n {
             wrapped_event = quote!{ #either_ident::First(#wrapped_event) };
         }
 
@@ -460,7 +518,6 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
             let mut out_handler = None;
 
             for (f_n, f) in data_struct_fields.iter().enumerate() {
-
                 let f_name = match f.ident {
                     Some(ref i) => quote! { self.#i },
                     None => quote! { self.#f_n },
@@ -492,16 +549,31 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
                 }
             }
         } else {
+            // If the `NetworkBehaviour`'s `OutEvent` is generated by the derive macro, wrap the sub
+            // `NetworkBehaviour` `OutEvent` in the variant of the generated `OutEvent`. If the
+            // `NetworkBehaviour`'s `OutEvent` is provided by the user, use the corresponding `From`
+            // implementation.
+            let into_out_event = if out_event_definition.is_some() {
+                let event_variant: syn::Variant = syn::parse_str(
+                    &field
+                        .to_string()
+                        .to_upper_camel_case()
+                ).unwrap();
+                quote! { #out_event_name::#event_variant(event) }
+            } else {
+                quote! { event.into() }
+            };
+
             quote! {
                 std::task::Poll::Ready(#network_behaviour_action::GenerateEvent(event)) => {
-                    return std::task::Poll::Ready(#network_behaviour_action::GenerateEvent(event.into()))
+                    return std::task::Poll::Ready(#network_behaviour_action::GenerateEvent(#into_out_event))
                 }
             }
         };
 
         Some(quote!{
             loop {
-                match #trait_to_impl::poll(&mut #field_name, cx, poll_params) {
+                match #trait_to_impl::poll(&mut self.#field, cx, poll_params) {
                     #generate_event_match_arm
                     std::task::Poll::Ready(#network_behaviour_action::Dial { opts, handler: provided_handler }) => {
                         return std::task::Poll::Ready(#network_behaviour_action::Dial { opts, handler: #provided_handler_and_new_handlers });
@@ -527,11 +599,13 @@ fn build_struct(ast: &DeriveInput, data_struct: &DataStruct) -> TokenStream {
 
     // Now the magic happens.
     let final_quote = quote! {
+        #out_event_definition
+
         impl #impl_generics #trait_to_impl for #name #ty_generics
         #where_clause
         {
             type ConnectionHandler = #connection_handler_ty;
-            type OutEvent = #out_event;
+            type OutEvent = #out_event_name #ty_generics;
 
             fn new_handler(&mut self) -> Self::ConnectionHandler {
                 use #into_connection_handler;