Add dev-rpc middleware (#640)

* Add dev-rpc middleware

* Dont run dev-rpc tests with celo

* providers: clean up match statement

* providers: fix clippy lint

* doc(providers) doctest and changelog for DevRpcMiddleware

CHANGELOG.md

@@ -61,6 +61,8 @@
 - Fix `http Provider` data race when generating new request `id`s.
 - Add support for `net_version` RPC method.
   [595](https://github.com/gakonst/ethers-rs/pull/595)
+- Add support for `evm_snapshot` and `evm_revert` dev RPC methods.
+  [640](https://github.com/gakonst/ethers-rs/pull/640)
 
 ### Unreleased
 

Cargo.toml

@@ -67,6 +67,7 @@ ws = ["ethers-providers/ws"]
 ipc = ["ethers-providers/ipc"]
 rustls = ["ethers-providers/rustls"]
 openssl = ["ethers-providers/openssl"]
+dev-rpc = ["ethers-providers/dev-rpc"]
 ## signers
 ledger = ["ethers-signers/ledger"]
 yubi = ["ethers-signers/yubi"]

ethers-providers/Cargo.toml

@@ -65,3 +65,4 @@ ipc = ["tokio", "tokio/io-util", "tokio-util", "bytes"]
 
 openssl = ["tokio-tungstenite/native-tls", "reqwest/native-tls"]
 rustls = ["tokio-tungstenite/rustls-tls", "reqwest/rustls-tls"]
+dev-rpc = []

ethers-providers/src/lib.rs

@@ -32,6 +32,10 @@ use std::{error::Error, fmt::Debug, future::Future, pin::Pin, str::FromStr};
 
 pub use provider::{FilterKind, Provider, ProviderError};
 
+// feature-enabled support for dev-rpc methods
+#[cfg(feature = "dev-rpc")]
+pub use provider::dev_rpc::DevRpcMiddleware;
+
 /// A simple gas escalation policy
 pub type EscalationPolicy = Box<dyn Fn(U256, usize) -> U256 + Send + Sync>;
 

ethers-providers/src/provider.rs

@@ -1021,6 +1021,183 @@ impl TryFrom<String> for Provider<HttpProvider> {
     }
 }
 
+/// A middleware supporting development-specific JSON RPC methods
+///
+/// # Example
+///
+///```
+/// use ethers_providers::{Provider, Http, Middleware, DevRpcMiddleware};
+/// use ethers_core::types::TransactionRequest;
+/// use ethers_core::utils::Ganache;
+/// use std::convert::TryFrom;
+///
+/// # #[tokio::main]
+/// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
+/// let ganache = Ganache::new().spawn();
+/// let provider = Provider::<Http>::try_from(ganache.endpoint()).unwrap();
+/// let client = DevRpcMiddleware::new(provider);
+///
+/// // snapshot the initial state
+/// let block0 = client.get_block_number().await.unwrap();
+/// let snap_id = client.snapshot().await.unwrap();
+///
+/// // send a transaction
+/// let accounts = client.get_accounts().await?;
+/// let from = accounts[0];
+/// let to = accounts[1];
+/// let balance_before = client.get_balance(to, None).await?;
+/// let tx = TransactionRequest::new().to(to).value(1000).from(from);
+/// client.send_transaction(tx, None).await?.await?;
+/// let balance_after = client.get_balance(to, None).await?;
+/// assert_eq!(balance_after, balance_before + 1000);
+///
+/// // revert to snapshot
+/// client.revert_to_snapshot(snap_id).await.unwrap();
+/// let balance_after_revert = client.get_balance(to, None).await?;
+/// assert_eq!(balance_after_revert, balance_before);
+/// # Ok(())
+/// # }
+/// ```
+#[cfg(feature = "dev-rpc")]
+pub mod dev_rpc {
+    use crate::{FromErr, Middleware, ProviderError};
+    use async_trait::async_trait;
+    use ethers_core::types::U256;
+    use thiserror::Error;
+
+    use std::fmt::Debug;
+
+    #[derive(Clone, Debug)]
+    pub struct DevRpcMiddleware<M>(M);
+
+    #[derive(Error, Debug)]
+    pub enum DevRpcMiddlewareError<M: Middleware> {
+        #[error("{0}")]
+        MiddlewareError(M::Error),
+
+        #[error("{0}")]
+        ProviderError(ProviderError),
+
+        #[error("Could not revert to snapshot")]
+        NoSnapshot,
+    }
+
+    #[async_trait]
+    impl<M: Middleware> Middleware for DevRpcMiddleware<M> {
+        type Error = DevRpcMiddlewareError<M>;
+        type Provider = M::Provider;
+        type Inner = M;
+
+        fn inner(&self) -> &M {
+            &self.0
+        }
+    }
+
+    impl<M: Middleware> FromErr<M::Error> for DevRpcMiddlewareError<M> {
+        fn from(src: M::Error) -> DevRpcMiddlewareError<M> {
+            DevRpcMiddlewareError::MiddlewareError(src)
+        }
+    }
+
+    impl<M> From<ProviderError> for DevRpcMiddlewareError<M>
+    where
+        M: Middleware,
+    {
+        fn from(src: ProviderError) -> Self {
+            Self::ProviderError(src)
+        }
+    }
+
+    impl<M: Middleware> DevRpcMiddleware<M> {
+        pub fn new(inner: M) -> Self {
+            Self(inner)
+        }
+
+        // both ganache and hardhat increment snapshot id even if no state has changed
+        pub async fn snapshot(&self) -> Result<U256, DevRpcMiddlewareError<M>> {
+            self.provider().request::<(), U256>("evm_snapshot", ()).await.map_err(From::from)
+        }
+
+        pub async fn revert_to_snapshot(&self, id: U256) -> Result<(), DevRpcMiddlewareError<M>> {
+            let ok = self
+                .provider()
+                .request::<[U256; 1], bool>("evm_revert", [id])
+                .await
+                .map_err(DevRpcMiddlewareError::ProviderError)?;
+            if ok {
+                Ok(())
+            } else {
+                Err(DevRpcMiddlewareError::NoSnapshot)
+            }
+        }
+    }
+    #[cfg(test)]
+    // Celo blocks can not get parsed when used with Ganache
+    #[cfg(not(feature = "celo"))]
+    mod tests {
+        use super::*;
+        use crate::{Http, Provider};
+        use ethers_core::utils::Ganache;
+        use std::convert::TryFrom;
+
+        #[tokio::test]
+        async fn test_snapshot() {
+            // launch ganache
+            let ganache = Ganache::new().spawn();
+            let provider = Provider::<Http>::try_from(ganache.endpoint()).unwrap();
+            let client = DevRpcMiddleware::new(provider);
+
+            // snapshot initial state
+            let block0 = client.get_block_number().await.unwrap();
+            let time0 = client.get_block(block0).await.unwrap().unwrap().timestamp;
+            let snap_id0 = client.snapshot().await.unwrap();
+
+            // mine a new block
+            client.provider().mine(1).await.unwrap();
+
+            // snapshot state
+            let block1 = client.get_block_number().await.unwrap();
+            let time1 = client.get_block(block1).await.unwrap().unwrap().timestamp;
+            let snap_id1 = client.snapshot().await.unwrap();
+
+            // mine some blocks
+            client.provider().mine(5).await.unwrap();
+
+            // snapshot state
+            let block2 = client.get_block_number().await.unwrap();
+            let time2 = client.get_block(block2).await.unwrap().unwrap().timestamp;
+            let snap_id2 = client.snapshot().await.unwrap();
+
+            // mine some blocks
+            client.provider().mine(5).await.unwrap();
+
+            // revert_to_snapshot should reset state to snap id
+            client.revert_to_snapshot(snap_id2).await.unwrap();
+            let block = client.get_block_number().await.unwrap();
+            let time = client.get_block(block).await.unwrap().unwrap().timestamp;
+            assert_eq!(block, block2);
+            assert_eq!(time, time2);
+
+            client.revert_to_snapshot(snap_id1).await.unwrap();
+            let block = client.get_block_number().await.unwrap();
+            let time = client.get_block(block).await.unwrap().unwrap().timestamp;
+            assert_eq!(block, block1);
+            assert_eq!(time, time1);
+
+            // revert_to_snapshot should throw given non-existent or
+            // previously used snapshot
+            let result = client.revert_to_snapshot(snap_id1).await;
+            assert!(result.is_err());
+
+            client.revert_to_snapshot(snap_id0).await.unwrap();
+            let block = client.get_block_number().await.unwrap();
+            let time = client.get_block(block).await.unwrap().unwrap().timestamp;
+            assert_eq!(block, block0);
+            assert_eq!(time, time0);
+        }
+    }
+}
+
 #[cfg(test)]
 #[cfg(not(target_arch = "wasm32"))]
 mod tests {