feat(provider): add RwClient (#1016)

* feat(provider): add RwClient

* docs: fix failing doc test

ethers-providers/src/provider.rs

@@ -3,7 +3,7 @@ use crate::{
     pubsub::{PubsubClient, SubscriptionStream},
     stream::{FilterWatcher, DEFAULT_POLL_INTERVAL},
     FromErr, Http as HttpProvider, JsonRpcClient, JsonRpcClientWrapper, MockProvider,
-    PendingTransaction, QuorumProvider, SyncingStatus,
+    PendingTransaction, QuorumProvider, RwClient, SyncingStatus,
 };
 
 #[cfg(feature = "celo")]
@@ -1235,6 +1235,19 @@ impl Provider<crate::Ipc> {
     }
 }
 
+impl<Read, Write> Provider<RwClient<Read, Write>>
+where
+    Read: JsonRpcClient + 'static,
+    <Read as JsonRpcClient>::Error: Sync + Send + 'static,
+    Write: JsonRpcClient + 'static,
+    <Write as JsonRpcClient>::Error: Sync + Send + 'static,
+{
+    /// Creates a new [Provider] with a [RwClient]
+    pub fn rw(r: Read, w: Write) -> Self {
+        Self::new(RwClient::new(r, w))
+    }
+}
+
 impl<T: JsonRpcClientWrapper> Provider<QuorumProvider<T>> {
     /// Provider that uses a quorum
     pub fn quorum(inner: QuorumProvider<T>) -> Self {

ethers-providers/src/transports/mod.rs

@@ -36,5 +36,8 @@ mod quorum;
 pub(crate) use quorum::JsonRpcClientWrapper;
 pub use quorum::{Quorum, QuorumError, QuorumProvider, WeightedProvider};
 
+mod rw;
+pub use rw::{RwClient, RwClientError};
+
 mod mock;
 pub use mock::{MockError, MockProvider};

ethers-providers/src/transports/rw.rs

@@ -0,0 +1,127 @@
+//! A [JsonRpcClient] implementation that serves as a wrapper around two different [JsonRpcClient]
+//! and uses a dedicated client for read and the other for write operations
+
+use crate::{provider::ProviderError, JsonRpcClient};
+
+use async_trait::async_trait;
+
+use serde::{de::DeserializeOwned, Serialize};
+
+use thiserror::Error;
+
+/// A client contains two clients.
+///
+/// One is used for _read_ operations
+/// One is used for _write_ operations that consume gas `["eth_sendTransaction",
+/// "eth_sendRawTransaction"]`
+///
+/// **Note**: if the method is unknown this client falls back to the _read_ client
+// # Example
+#[derive(Debug, Clone)]
+pub struct RwClient<Read, Write> {
+    /// client used to read
+    r: Read,
+    /// client used to write
+    w: Write,
+}
+
+impl<Read, Write> RwClient<Read, Write> {
+    /// Creates a new client using two different clients
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// # use url::Url;
+    ///  async fn t(){
+    /// use ethers_providers::{Http, RwClient, Ws};
+    /// let http = Http::new(Url::parse("http://localhost:8545").unwrap());
+    /// let ws = Ws::connect("ws://localhost:8545").await.unwrap();
+    /// let rw = RwClient::new(http, ws);
+    /// # }
+    /// ```
+    pub fn new(r: Read, w: Write) -> RwClient<Read, Write> {
+        Self { r, w }
+    }
+
+    /// Returns the client used for read operations
+    pub fn read_client(&self) -> &Read {
+        &self.r
+    }
+
+    /// Returns the client used for read operations
+    pub fn write_client(&self) -> &Write {
+        &self.w
+    }
+
+    /// Returns a new `RwClient` with transposed clients
+    pub fn transpose(self) -> RwClient<Write, Read> {
+        let RwClient { r, w } = self;
+        RwClient::new(w, r)
+    }
+
+    /// Consumes the client and returns the underlying clients
+    pub fn split(self) -> (Read, Write) {
+        let RwClient { r, w } = self;
+        (r, w)
+    }
+}
+
+#[derive(Error, Debug)]
+/// Error thrown when using either read or write client
+pub enum RwClientError<Read, Write>
+where
+    Read: JsonRpcClient,
+    <Read as JsonRpcClient>::Error: Sync + Send + 'static,
+    Write: JsonRpcClient,
+    <Write as JsonRpcClient>::Error: Sync + Send + 'static,
+{
+    /// Thrown if the _read_ request failed
+    #[error(transparent)]
+    Read(Read::Error),
+    #[error(transparent)]
+    /// Thrown if the _write_ request failed
+    Write(Write::Error),
+}
+
+impl<Read, Write> From<RwClientError<Read, Write>> for ProviderError
+where
+    Read: JsonRpcClient + 'static,
+    <Read as JsonRpcClient>::Error: Sync + Send + 'static,
+    Write: JsonRpcClient + 'static,
+    <Write as JsonRpcClient>::Error: Sync + Send + 'static,
+{
+    fn from(src: RwClientError<Read, Write>) -> Self {
+        ProviderError::JsonRpcClientError(Box::new(src))
+    }
+}
+
+#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
+#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
+impl<Read, Write> JsonRpcClient for RwClient<Read, Write>
+where
+    Read: JsonRpcClient + 'static,
+    <Read as JsonRpcClient>::Error: Sync + Send + 'static,
+    Write: JsonRpcClient + 'static,
+    <Write as JsonRpcClient>::Error: Sync + Send + 'static,
+{
+    type Error = RwClientError<Read, Write>;
+
+    /// Sends a POST request with the provided method and the params serialized as JSON
+    /// over HTTP
+    async fn request<T: Serialize + Send + Sync, R: DeserializeOwned>(
+        &self,
+        method: &str,
+        params: T,
+    ) -> Result<R, Self::Error>
+    where
+        T: std::fmt::Debug + Serialize + Send + Sync,
+        R: DeserializeOwned,
+    {
+        match method {
+            "eth_sendTransaction" | "eth_sendRawTransaction" => {
+                self.w.request(method, params).await.map_err(RwClientError::Write)
+            }
+            _ => self.r.request(method, params).await.map_err(RwClientError::Read),
+        }
+    }
+}

examples/rw.rs

@@ -0,0 +1,19 @@
+//! Example usage for the `RwClinet` that uses a didicated client to send transaction and nother one
+//! for read ops
+
+use ethers::{prelude::*, utils::Ganache};
+use std::{str::FromStr, time::Duration};
+
+#[tokio::main]
+async fn main() -> eyre::Result<()> {
+    let ganache = Ganache::new().spawn();
+
+    let http = Http::from_str(&ganache.endpoint())?;
+    let ws = Ws::connect(ganache.ws_endpoint()).await?;
+
+    let provider = Provider::rw(http, ws).interval(Duration::from_millis(10u64));
+
+    dbg!(provider.get_accounts().await?);
+
+    Ok(())
+}