feature: allow event builder to stream with meta (#1483)

* feature: allow event builder to stream with meta

* doc: improve rustdoc

* feature: subscribe_with_meta

* chore: fmt

CHANGELOG.md

@@ -237,6 +237,8 @@
 
 ### Unreleased
 
+- Add `Event::stream_with_meta` and `Event::subscribe_with_meta`
+  [#1483](https://github.com/gakonst/ethers-rs/pull/1483)
 - Added tx builder methods to `ContractFactory`
   [#1289](https://github.com/gakonst/ethers-rs/pull/1289)
 - Relax Clone requirements when Arc<Middleware> is used

ethers-contract/src/event.rs

@@ -164,6 +164,26 @@ where
             self.provider.watch(&self.filter).await.map_err(ContractError::MiddlewareError)?;
         Ok(EventStream::new(filter.id, filter, Box::new(move |log| self.parse_log(log))))
     }
+
+    /// As [`Self::stream`], but does not discard [`Log`] metadata.
+    pub async fn stream_with_meta(
+        &'a self,
+    ) -> Result<
+        // Wraps the FilterWatcher with a mapping to the event
+        EventStream<'a, FilterWatcher<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
+        ContractError<M>,
+    > {
+        let filter =
+            self.provider.watch(&self.filter).await.map_err(ContractError::MiddlewareError)?;
+        Ok(EventStream::new(
+            filter.id,
+            filter,
+            Box::new(move |log| {
+                let meta = LogMeta::from(&log);
+                Ok((self.parse_log(log)?, meta))
+            }),
+        ))
+    }
 }
 
 impl<'a, M, D> Event<'a, M, D>
@@ -189,6 +209,28 @@ where
             .map_err(ContractError::MiddlewareError)?;
         Ok(EventStream::new(filter.id, filter, Box::new(move |log| self.parse_log(log))))
     }
+
+    pub async fn subscribe_with_meta(
+        &'a self,
+    ) -> Result<
+        // Wraps the SubscriptionStream with a mapping to the event
+        EventStream<'a, SubscriptionStream<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
+        ContractError<M>,
+    > {
+        let filter = self
+            .provider
+            .subscribe_logs(&self.filter)
+            .await
+            .map_err(ContractError::MiddlewareError)?;
+        Ok(EventStream::new(
+            filter.id,
+            filter,
+            Box::new(move |log| {
+                let meta = LogMeta::from(&log);
+                Ok((self.parse_log(log)?, meta))
+            }),
+        ))
+    }
 }
 
 impl<M, D> Event<'_, M, D>