feature: providererror conversion to middleware error (#1920)

* feature: providererror conversion to middleware error

* chore: update changelog

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## ethers-core
 
 ### Unreleased
+
 - Graceful handling of WebSocket transport errors [#1889](https://github.com/gakonst/ethers-rs/issues/1889) [#1815](https://github.com/gakonst/ethers-rs/issues/1815)
 - `MiddlewareBuilder` trait to instantiate a `Provider` as `Middleware` layers.
 - An `Event` builder can be instantiated specifying the event filter type, without the need to instantiate a contract.
@@ -105,6 +106,7 @@
 ## ethers-contract-abigen
 
 ### Unreleased
+
 - Fix Cargo.toml generation issue that could cause dependency conflicts [#1852](https://github.com/gakonst/ethers-rs/pull/1852)
 - Use corresponding rust structs for event fields if they're solidity structs [#1674](https://github.com/gakonst/ethers-rs/pull/1674)
 - Add `ContractFilter` to filter contracts in `MultiAbigen` [#1564](https://github.com/gakonst/ethers-rs/pull/1564)
@@ -222,6 +224,8 @@
 
 ### Unreleased
 
+- Convert provider errors to arbitrary middleware errors
+  [#1920](https://github.com/gakonst/ethers-rs/pull/1920)
 - Add a subset of the `admin` namespace
   [1880](https://github.com/gakonst/ethers-rs/pull/1880)
 - Return String for net version

ethers-providers/src/lib.rs

@@ -159,6 +159,13 @@ pub trait Middleware: Sync + Send + Debug {
     /// The next middleware in the stack
     fn inner(&self) -> &Self::Inner;
 
+    /// Convert a provider error into the associated error type by successively
+    /// converting it to every intermediate middleware error
+    fn convert_err(p: ProviderError) -> Self::Error {
+        let e = <Self as Middleware>::Inner::convert_err(p);
+        FromErr::from(e)
+    }
+
     /// The HTTP or Websocket provider.
     fn provider(&self) -> &Provider<Self::Provider> {
         self.inner().provider()

ethers-providers/src/provider.rs

@@ -304,6 +304,11 @@ impl<P: JsonRpcClient> Middleware for Provider<P> {
         self
     }
 
+    fn convert_err(p: ProviderError) -> Self::Error {
+        // no conversion necessary
+        p
+    }
+
     fn default_sender(&self) -> Option<Address> {
         self.from
     }