feat: extend Middleware trait customized for celo (#314)

* Add CeloMiddleware trait

* change types of block number and returned keys

ethers-providers/src/lib.rs

@@ -561,3 +561,17 @@ pub trait Middleware: Sync + Send + Debug {
             .map_err(FromErr::from)
     }
 }
+
+#[cfg(feature = "celo")]
+#[async_trait]
+pub trait CeloMiddleware: Middleware {
+    async fn get_validators_bls_public_keys(
+        &self,
+        block: Option<BlockId>,
+    ) -> Result<Vec<Vec<u8>>, ProviderError> {
+        self.provider()
+            .get_validators_bls_public_keys(block)
+            .await
+            .map_err(FromErr::from)
+    }
+}

ethers-providers/src/provider.rs

@@ -15,6 +15,8 @@ use ethers_core::{
     utils,
 };
 
+#[cfg(feature = "celo")]
+use crate::CeloMiddleware;
 use crate::Middleware;
 use async_trait::async_trait;
 use hex::FromHex;
@@ -150,6 +152,19 @@ impl<P: JsonRpcClient> Provider<P> {
     }
 }
 
+#[cfg(feature = "celo")]
+#[async_trait]
+impl<P: JsonRpcClient> CeloMiddleware for Provider<P> {
+    async fn get_validators_bls_public_keys(
+        &self,
+        block: Option<BlockId>,
+    ) -> Result<Vec<Vec<u8>>, ProviderError> {
+        let block = utils::serialize(&block.unwrap_or_else(|| BlockNumber::Latest.into()));
+        self.request("istanbul_getValidatorsBLSPublicKeys", [block])
+            .await
+    }
+}
+
 #[async_trait]
 impl<P: JsonRpcClient> Middleware for Provider<P> {
     type Error = ProviderError;