Allow trait bounds to be overridden in macro (#808)

* Parse user defined client_bounds and server_bounds

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Use custom user defined bounds if provided

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Add provided where clause to the custom bounds

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Add proc_macro with bounds example

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Check against client_bounds wihtout client implementation

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Add ui test for empty bounds

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Add ui test to check bounds without implementation

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Add bounds documentation

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* rpc_macro: Remove `WherePredicate` from parsing

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* ui: Add test that compiles

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Rename rendered `T` to avoid collision with user provided generic

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Modify UI correct rpc_bounds test to call server's methods

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples/examples/proc_macro_bounds.rs

@@ -0,0 +1,90 @@
+// Copyright 2019-2021 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any
+// person obtaining a copy of this software and associated
+// documentation files (the "Software"), to deal in the
+// Software without restriction, including without
+// limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice
+// shall be included in all copies or substantial portions
+// of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+use std::net::SocketAddr;
+
+use jsonrpsee::core::{async_trait, Error};
+use jsonrpsee::proc_macros::rpc;
+use jsonrpsee::ws_client::WsClientBuilder;
+use jsonrpsee::ws_server::{WsServerBuilder, WsServerHandle};
+
+type ExampleHash = [u8; 32];
+
+pub trait Config {
+	type Hash: Send + Sync + 'static;
+}
+
+impl Config for ExampleHash {
+	type Hash = Self;
+}
+
+/// The RPC macro requires `DeserializeOwned` for output types for the client implementation, while the
+/// server implementation requires output types to be bounded by `Serialize`.
+///
+/// In this example, we don't want the `Conf` to be bounded by default to
+/// `Conf : Send + Sync + 'static + jsonrpsee::core::DeserializeOwned` for client implementation and
+/// `Conf : Send + Sync + 'static + jsonrpsee::core::Serialize` for server implementation.
+///
+/// Explicitly, specify client and server bounds to handle the `Serialize` and `DeserializeOwned` cases
+/// just for the `Conf::hash` part.
+#[rpc(server, client, namespace = "foo", client_bounds(T::Hash: jsonrpsee::core::DeserializeOwned), server_bounds(T::Hash: jsonrpsee::core::Serialize))]
+pub trait Rpc<T: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> Result<T::Hash, Error>;
+}
+
+pub struct RpcServerImpl;
+
+#[async_trait]
+impl RpcServer<ExampleHash> for RpcServerImpl {
+	fn method(&self) -> Result<<ExampleHash as Config>::Hash, Error> {
+		Ok([0u8; 32])
+	}
+}
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+	tracing_subscriber::FmtSubscriber::builder()
+		.with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
+		.try_init()
+		.expect("setting default subscriber failed");
+
+	let (server_addr, _handle) = run_server().await?;
+	let url = format!("ws://{}", server_addr);
+
+	let client = WsClientBuilder::default().build(&url).await?;
+	assert_eq!(RpcClient::<ExampleHash>::method(&client).await.unwrap(), [0u8; 32]);
+
+	Ok(())
+}
+
+async fn run_server() -> anyhow::Result<(SocketAddr, WsServerHandle)> {
+	let server = WsServerBuilder::default().build("127.0.0.1:0").await?;
+
+	let addr = server.local_addr()?;
+	let handle = server.start(RpcServerImpl.into_rpc())?;
+	Ok((addr, handle))
+}

proc-macros/src/helpers.rs

@@ -30,7 +30,7 @@ use crate::visitor::{FindAllParams, FindSubscriptionParams};
 use proc_macro2::{Span, TokenStream as TokenStream2};
 use proc_macro_crate::{crate_name, FoundCrate};
 use quote::quote;
-use syn::{parse_quote, punctuated::Punctuated, visit::Visit, Token};
+use syn::{parse_quote, punctuated::Punctuated, token::Comma, visit::Visit, Token, WherePredicate};
 
 /// Search for client-side `jsonrpsee` in `Cargo.toml`.
 pub(crate) fn find_jsonrpsee_client_crate() -> Result<proc_macro2::TokenStream, syn::Error> {
@@ -91,10 +91,21 @@ pub(crate) fn generate_where_clause(
 	item_trait: &syn::ItemTrait,
 	sub_tys: &[syn::Type],
 	is_client: bool,
+	bounds: Option<&Punctuated<WherePredicate, Comma>>,
 ) -> Vec<syn::WherePredicate> {
 	let visitor = visit_trait(item_trait, sub_tys);
 	let additional_where_clause = item_trait.generics.where_clause.clone();
 
+	if let Some(custom_bounds) = bounds {
+		let mut bounds = additional_where_clause
+			.map(|where_clause| where_clause.predicates.into_iter().collect())
+			.unwrap_or(Vec::new());
+
+		bounds.extend(custom_bounds.iter().cloned());
+
+		return bounds;
+	}
+
 	item_trait
 		.generics
 		.type_params()

proc-macros/src/lib.rs

@@ -145,6 +145,10 @@ pub(crate) mod visitor;
 ///   implementation's methods conveniently.
 /// - `namespace`: add a prefix to all the methods and subscriptions in this RPC. For example, with namespace `foo` and
 ///   method `spam`, the resulting method name will be `foo_spam`.
+/// - `server_bounds`: replace *all* auto-generated trait bounds with the user-defined ones for the server
+///   implementation.
+/// - `client_bounds`: replace *all* auto-generated trait bounds with the user-defined ones for the client
+///   implementation.
 ///
 /// **Trait requirements:**
 ///

proc-macros/src/render_client.rs

@@ -36,7 +36,7 @@ impl RpcDescription {
 		let sub_tys: Vec<syn::Type> = self.subscriptions.clone().into_iter().map(|s| s.item).collect();
 
 		let trait_name = quote::format_ident!("{}Client", &self.trait_def.ident);
-		let where_clause = generate_where_clause(&self.trait_def, &sub_tys, true);
+		let where_clause = generate_where_clause(&self.trait_def, &sub_tys, true, self.client_bounds.as_ref());
 		let type_idents = self.trait_def.generics.type_params().collect::<Vec<&TypeParam>>();
 		let (impl_generics, type_generics, _) = self.trait_def.generics.split_for_impl();
 
@@ -63,7 +63,7 @@ impl RpcDescription {
 				#(#sub_impls)*
 			}
 
-			impl<T #(,#type_idents)*> #trait_name #type_generics for T where T: #super_trait #(,#where_clause)* {}
+			impl<TypeJsonRpseeInteral #(,#type_idents)*> #trait_name #type_generics for TypeJsonRpseeInteral where TypeJsonRpseeInteral: #super_trait #(,#where_clause)* {}
 		};
 
 		Ok(trait_impl)

proc-macros/src/render_server.rs

@@ -287,7 +287,7 @@ impl RpcDescription {
 								and adds them into a single `RpcModule`.";
 
 		let sub_tys: Vec<syn::Type> = self.subscriptions.clone().into_iter().map(|s| s.item).collect();
-		let where_clause = generate_where_clause(&self.trait_def, &sub_tys, false);
+		let where_clause = generate_where_clause(&self.trait_def, &sub_tys, false, self.server_bounds.as_ref());
 
 		// NOTE(niklasad1): empty where clause is valid rust syntax.
 		Ok(quote! {

proc-macros/src/rpc_macro.rs

@@ -220,20 +220,41 @@ pub struct RpcDescription {
 	pub(crate) methods: Vec<RpcMethod>,
 	/// List of RPC subscriptions defined in the trait.
 	pub(crate) subscriptions: Vec<RpcSubscription>,
+	/// Optional user defined trait bounds for the client implementation.
+	pub(crate) client_bounds: Option<Punctuated<syn::WherePredicate, Token![,]>>,
+	/// Optional user defined trait bounds for the server implementation.
+	pub(crate) server_bounds: Option<Punctuated<syn::WherePredicate, Token![,]>>,
 }
 
 impl RpcDescription {
 	pub fn from_item(attr: Attribute, mut item: syn::ItemTrait) -> syn::Result<Self> {
-		let [client, server, namespace] = AttributeMeta::parse(attr)?.retain(["client", "server", "namespace"])?;
+		let [client, server, namespace, client_bounds, server_bounds] =
+			AttributeMeta::parse(attr)?.retain(["client", "server", "namespace", "client_bounds", "server_bounds"])?;
 
 		let needs_server = optional(server, Argument::flag)?.is_some();
 		let needs_client = optional(client, Argument::flag)?.is_some();
 		let namespace = optional(namespace, Argument::string)?;
+		let client_bounds = optional(client_bounds, Argument::group)?;
+		let server_bounds = optional(server_bounds, Argument::group)?;
 
 		if !needs_server && !needs_client {
 			return Err(syn::Error::new_spanned(&item.ident, "Either 'server' or 'client' attribute must be applied"));
 		}
 
+		if client_bounds.is_some() && !needs_client {
+			return Err(syn::Error::new_spanned(
+				&item.ident,
+				"Attribute 'client' must be specified with 'client_bounds'",
+			));
+		}
+
+		if server_bounds.is_some() && !needs_server {
+			return Err(syn::Error::new_spanned(
+				&item.ident,
+				"Attribute 'server' must be specified with 'server_bounds'",
+			));
+		}
+
 		let jsonrpsee_client_path = crate::helpers::find_jsonrpsee_client_crate().ok();
 		let jsonrpsee_server_path = crate::helpers::find_jsonrpsee_server_crate().ok();
 
@@ -313,6 +334,8 @@ impl RpcDescription {
 			trait_def: item,
 			methods,
 			subscriptions,
+			client_bounds,
+			server_bounds,
 		})
 	}
 

proc-macros/tests/ui/correct/rpc_bounds.rs

@@ -0,0 +1,90 @@
+//! Example of using proc macro to generate working client and server with bounds applied.
+
+use std::net::SocketAddr;
+
+use jsonrpsee::core::{async_trait, RpcResult};
+use jsonrpsee::proc_macros::rpc;
+use jsonrpsee::ws_client::*;
+use jsonrpsee::ws_server::WsServerBuilder;
+
+pub trait Config {
+	type Hash: Send + Sync + 'static;
+	type NotUsed;
+}
+
+type ExampleHash = [u8; 32];
+impl Config for ExampleHash {
+	type Hash = Self;
+	type NotUsed = ();
+}
+
+/// Client only RPC.
+#[rpc(client, namespace = "foo", client_bounds(Conf::Hash: jsonrpsee::core::DeserializeOwned))]
+pub trait MyRpcC<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> RpcResult<Conf::Hash>;
+}
+
+/// Server only RPC.
+#[rpc(server, namespace = "foo", server_bounds(Conf::Hash: jsonrpsee::core::Serialize))]
+pub trait MyRpcS<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> RpcResult<Conf::Hash>;
+}
+
+/// Client and server RPC.
+#[rpc(server, client, namespace = "foo", client_bounds(Conf::Hash: jsonrpsee::core::DeserializeOwned), server_bounds(Conf::Hash: jsonrpsee::core::Serialize))]
+pub trait MyRpcSC<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> RpcResult<Conf::Hash>;
+}
+
+/// Implementation for the `MyRpcS` trait (server only).
+pub struct ServerOnlyImpl;
+#[async_trait]
+impl MyRpcSServer<ExampleHash> for ServerOnlyImpl {
+	fn method(&self) -> RpcResult<<ExampleHash as Config>::Hash> {
+		Ok([0u8; 32])
+	}
+}
+
+/// Implementation for the `MyRpcSC` trait (client server rpc).
+pub struct ServerClientServerImpl;
+#[async_trait]
+impl MyRpcSCServer<ExampleHash> for ServerClientServerImpl {
+	fn method(&self) -> RpcResult<<ExampleHash as Config>::Hash> {
+		Ok([0u8; 32])
+	}
+}
+
+pub async fn websocket_servers() -> (SocketAddr, SocketAddr) {
+	// Start server from `MyRpcS` trait.
+	let server = WsServerBuilder::default().build("127.0.0.1:0").await.unwrap();
+	let addr_server_only = server.local_addr().unwrap();
+	server.start(ServerOnlyImpl.into_rpc()).unwrap();
+
+	// Start server from `MyRpcSC` trait.
+	let server = WsServerBuilder::default().build("127.0.0.1:0").await.unwrap();
+	let addr_server_client = server.local_addr().unwrap();
+	server.start(ServerClientServerImpl.into_rpc()).unwrap();
+
+	(addr_server_only, addr_server_client)
+}
+
+#[tokio::main]
+async fn main() {
+	let (server_addr, server_addr_w_client) = websocket_servers().await;
+	let (server_url, server_w_client_url) = (format!("ws://{}", server_addr), format!("ws://{}", server_addr_w_client));
+	let client = WsClientBuilder::default().build(&server_url).await.unwrap();
+	let client_second = WsClientBuilder::default().build(&server_w_client_url).await.unwrap();
+
+	// Use `MyRpcC` client to communicate to the `MyRpcS` server.
+	assert_eq!(MyRpcCClient::<ExampleHash>::method(&client).await.unwrap(), [0u8; 32]);
+	// Use `MyRpcC` client to communicate to the `MyRpcSC` server.
+	assert_eq!(MyRpcCClient::<ExampleHash>::method(&client_second).await.unwrap(), [0u8; 32]);
+
+	// Use `MyRpcSC` client to communicate to the `MyRpcS` server.
+	assert_eq!(MyRpcCClient::<ExampleHash>::method(&client).await.unwrap(), [0u8; 32]);
+	// Use `MyRpcSC` client to communicate to the `MyRpcSC` server.
+	assert_eq!(MyRpcSCClient::<ExampleHash>::method(&client_second).await.unwrap(), [0u8; 32]);
+}

proc-macros/tests/ui/incorrect/rpc/rpc_bounds_without_impl.rs

@@ -0,0 +1,19 @@
+use jsonrpsee::proc_macros::rpc;
+
+pub trait Config {
+	type Hash: Send + Sync + 'static;
+}
+
+#[rpc(server, client_bounds(), server_bounds(Conf::Hash: jsonrpsee::core::Serialize))]
+pub trait ClientBoundsForbidden<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> Result<Conf::Hash, Error>;
+}
+
+#[rpc(client, server_bounds(), client_bounds(Conf::Hash: jsonrpsee::core::DeserializeOwned))]
+pub trait ServerBoundsForbidden<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> Result<Conf::Hash, Error>;
+}
+
+fn main() {}

proc-macros/tests/ui/incorrect/rpc/rpc_bounds_without_impl.stderr

@@ -0,0 +1,11 @@
+error: Attribute 'client' must be specified with 'client_bounds'
+ --> tests/ui/incorrect/rpc/rpc_bounds_without_impl.rs:8:11
+  |
+8 | pub trait ClientBoundsForbidden<Conf: Config> {
+  |           ^^^^^^^^^^^^^^^^^^^^^
+
+error: Attribute 'server' must be specified with 'server_bounds'
+  --> tests/ui/incorrect/rpc/rpc_bounds_without_impl.rs:14:11
+   |
+14 | pub trait ServerBoundsForbidden<Conf: Config> {
+   |           ^^^^^^^^^^^^^^^^^^^^^

proc-macros/tests/ui/incorrect/rpc/rpc_empty_bounds.rs

@@ -0,0 +1,16 @@
+use jsonrpsee::proc_macros::rpc;
+use jsonrpsee::core::Error;
+
+pub trait Config {
+	type Hash: Send + Sync + 'static;
+}
+
+/// Client bound must be `Conf::Hash: jsonrpsee::core::DeserializeOwned`
+/// Server bound must be `Conf::Hash: jsonrpsee::core::Serialize`
+#[rpc(server, client, namespace = "foo", client_bounds(), server_bounds())]
+pub trait EmptyBounds<Conf: Config> {
+	#[method(name = "bar")]
+	fn method(&self) -> Result<Conf::Hash, Error>;
+}
+
+fn main() {}

proc-macros/tests/ui/incorrect/rpc/rpc_empty_bounds.stderr

@@ -0,0 +1,26 @@
+error[E0277]: the trait bound `<Conf as Config>::Hash: Serialize` is not satisfied
+   --> tests/ui/incorrect/rpc/rpc_empty_bounds.rs:10:1
+    |
+10  | #[rpc(server, client, namespace = "foo", client_bounds(), server_bounds())]
+    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Serialize` is not implemented for `<Conf as Config>::Hash`
+    |
+note: required by a bound in `RpcModule::<Context>::register_method`
+   --> $WORKSPACE/core/src/server/rpc_module.rs
+    |
+    |         R: Serialize,
+    |            ^^^^^^^^^ required by this bound in `RpcModule::<Context>::register_method`
+    = note: this error originates in the attribute macro `rpc` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `for<'de> <Conf as Config>::Hash: Deserialize<'de>` is not satisfied
+  --> tests/ui/incorrect/rpc/rpc_empty_bounds.rs:10:1
+   |
+10 | #[rpc(server, client, namespace = "foo", client_bounds(), server_bounds())]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'de> Deserialize<'de>` is not implemented for `<Conf as Config>::Hash`
+   |
+   = note: required because of the requirements on the impl of `DeserializeOwned` for `<Conf as Config>::Hash`
+note: required by a bound in `request`
+  --> $WORKSPACE/core/src/client/mod.rs
+   |
+   |         R: DeserializeOwned;
+   |            ^^^^^^^^^^^^^^^^ required by this bound in `request`
+   = note: this error originates in the attribute macro `rpc` (in Nightly builds, run with -Z macro-backtrace for more info)