Repository: gakonst/ethers-rs
Pull request #2105 (2023-02-01 21:02:09)

Prestwich/event no lifetime
Depends on #2082 

## Motivation

`FunctionCall` and `Event` both are created by `Contract` types via similar APIs. However, `Event` had a lifetime and borrowed the client, while `FunctionCall` cloned the client.

## Solution

 This PR updates `Event` to work as `FunctionCall` does.

Old Style:
- `Event<'a, M, D>`

New Style:
- `Event<B, M, D>`

## PR Checklist

-   [ ] Added Tests
-   [ ] Added Documentation
-   [ ] Updated the changelog
-   [x] Breaking changes


gakonst: dependency prs merged
prestwich: can't reproduce the CI failures locally :/
prestwich: this is ready for review. The current lint and doc failures seem to be unrelated? I can't reproduce locally either.
DaniPopes: > this is ready for review. The current lint and doc failures seem to be unrelated? I can't reproduce locally either.

I tried compiling with the latest nightly (`rustc 1.69.0-nightly (5b8f28453 2023-02-12)`) and the compiler panics at random points

After a few attempts I got it to compile at least with clippy and it found the `type parameter goes unused in function definition` in ethers-solc

Patch:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8ca82ecb..975a3c51 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -120,6 +120,7 @@
 
 ### Unreleased
 
+- Abigen now generates events with new `<B, M>` generic pattern [#2103](https://github.com/gakonst/ethers-rs/pull/2103)
 - 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)
@@ -300,6 +301,8 @@
 
 ### Unreleased
 
+- (Breaking) Make `Event` objects generic over borrow & remove lifetime
+  [#2105](https://github.com/gakonst/ethers-rs/pull/2105)
 - Make `Factory` objects generic over the borrow trait, to allow non-arc mware
   [#2103](https://github.com/gakonst/ethers-rs/pull/2103)
 - Make `Contract` objects generic over the borrow trait, to allow non-arc mware
diff --git a/ethers-contract/ethers-contract-abigen/src/contract/events.rs b/ethers-contract/ethers-contract-abigen/src/contract/events.rs
index f0e1d778..1dce3ef7 100644
--- a/ethers-contract/ethers-contract-abigen/src/contract/events.rs
+++ b/ethers-contract/ethers-contract-abigen/src/contract/events.rs
@@ -127,7 +127,7 @@ impl Context {
 
             quote! {
                 /// Returns an [`Event`](#ethers_contract::builders::Event) builder for all events of this contract
-                pub fn events(&self) -> #ethers_contract::builders::Event<M, #ty> {
+                pub fn events(&self) -> #ethers_contract::builders::Event<Arc<M>, M, #ty> {
                     self.0.event_with_filter(Default::default())
                 }
             }
@@ -235,7 +235,7 @@ impl Context {
 
         quote! {
             #[doc = #doc_str]
-            pub fn #function_name(&self) -> #ethers_contract::builders::Event<M, #struct_name> {
+            pub fn #function_name(&self) -> #ethers_contract::builders::Event<Arc<M>, M, #struct_name> {
                 self.0.event()
             }
         }
@@ -406,7 +406,7 @@ mod tests {
             #[doc = "Gets the contract's `Transfer` event"]
             pub fn transfer_event_filter(
                 &self
-            ) -> ::ethers_contract::builders::Event<M, TransferEventFilter> {
+            ) -> ::ethers_contract::builders::Event<Arc<M>, M, TransferEventFilter> {
                 self.0.event()
             }
         });
@@ -425,7 +425,9 @@ mod tests {
         let cx = test_context();
         assert_quote!(cx.expand_filter(&event), {
             #[doc = "Gets the contract's `Transfer` event"]
-            pub fn transfer_filter(&self) -> ::ethers_contract::builders::Event<M, TransferFilter> {
+            pub fn transfer_filter(
+                &self,
+            ) -> ::ethers_contract::builders::Event<Arc<M>, M, TransferFilter> {
                 self.0.event()
             }
         });
diff --git a/ethers-contract/src/contract.rs b/ethers-contract/src/contract.rs
index b842b120..2fa4f888 100644
--- a/ethers-contract/src/contract.rs
+++ b/ethers-contract/src/contract.rs
@@ -243,11 +243,12 @@ where
     /// Returns an [`Event`](crate::builders::Event) builder for the provided event.
     /// This function operates in a static context, then it does not require a `self`
     /// to reference to instantiate an [`Event`](crate::builders::Event) builder.
-    pub fn event_of_type<D: EthEvent>(client: &M) -> Event<M, D> {
+    pub fn event_of_type<D: EthEvent>(client: B) -> Event<B, M, D> {
         Event {
             provider: client,
             filter: Filter::new().event(&D::abi_signature()),
             datatype: PhantomData,
+            _m: PhantomData,
         }
     }
 }
@@ -262,27 +263,6 @@ where
         Self { base_contract: abi.into(), client, address: address.into(), _m: PhantomData }
     }
 
-    /// Returns an [`Event`](crate::builders::Event) builder for the provided event.
-    pub fn event<D: EthEvent>(&self) -> Event<M, D> {
-        self.event_with_filter(Filter::new().event(&D::abi_signature()))
-    }
-
-    /// Returns an [`Event`](crate::builders::Event) builder with the provided filter.
-    pub fn event_with_filter<D: EthLogDecode>(&self, filter: Filter) -> Event<M, D> {
-        Event {
-            provider: self.client.borrow(),
-            filter: filter.address(ValueOrArray::Value(self.address)),
-            datatype: PhantomData,
-        }
-    }
-
-    /// Returns an [`Event`](crate::builders::Event) builder with the provided name.
-    pub fn event_for_name<D: EthLogDecode>(&self, name: &str) -> Result<Event<M, D>, Error> {
-        // get the event's full name
-        let event = self.base_contract.abi.event(name)?;
-        Ok(self.event_with_filter(Filter::new().event(&event.abi_signature())))
-    }
-
     /// Returns a new contract instance using the provided client
     ///
     /// Clones `self` internally
@@ -321,6 +301,28 @@ where
     B: Clone + Borrow<M>,
     M: Middleware,
 {
+    /// Returns an [`Event`](crate::builders::Event) builder with the provided filter.
+    pub fn event_with_filter<D: EthLogDecode>(&self, filter: Filter) -> Event<B, M, D> {
+        Event {
+            provider: self.client.clone(),
+            filter: filter.address(ValueOrArray::Value(self.address)),
+            datatype: PhantomData,
+            _m: PhantomData,
+        }
+    }
+
+    /// Returns an [`Event`](crate::builders::Event) builder for the provided event.
+    pub fn event<D: EthEvent>(&self) -> Event<B, M, D> {
+        self.event_with_filter(Filter::new().event(&D::abi_signature()))
+    }
+
+    /// Returns an [`Event`](crate::builders::Event) builder with the provided name.
+    pub fn event_for_name<D: EthLogDecode>(&self, name: &str) -> Result<Event<B, M, D>, Error> {
+        // get the event's full name
+        let event = self.base_contract.abi.event(name)?;
+        Ok(self.event_with_filter(Filter::new().event(&event.abi_signature())))
+    }
+
     fn method_func<T: Tokenize, D: Detokenize>(
         &self,
         function: &Function,
diff --git a/ethers-contract/src/event.rs b/ethers-contract/src/event.rs
index c050749e..df529e6d 100644
--- a/ethers-contract/src/event.rs
+++ b/ethers-contract/src/event.rs
@@ -2,11 +2,22 @@
 
 use crate::{log::LogMeta, stream::EventStream, ContractError, EthLogDecode};
 use ethers_core::{
-    abi::{Address, Detokenize, RawLog},
+    abi::{Address, Detokenize, Error as AbiError, RawLog},
     types::{BlockNumber, Filter, Log, Topic, ValueOrArray, H256},
 };
 use ethers_providers::{FilterWatcher, Middleware, PubsubClient, SubscriptionStream};
-use std::{borrow::Cow, marker::PhantomData};
+use std::{
+    borrow::{Borrow, Cow},
+    marker::PhantomData,
+};
+
+/// Attempt to parse a log into a specific output type.
+pub fn parse_log<D>(log: Log) -> std::result::Result<D, AbiError>
+where
+    D: EthLogDecode,
+{
+    D::decode_log(&RawLog { topics: log.topics, data: log.data.to_vec() })
+}
 
 /// A trait for implementing event bindings
 pub trait EthEvent: Detokenize + Send + Sync {
@@ -31,12 +42,14 @@ pub trait EthEvent: Detokenize + Send + Sync {
     fn is_anonymous() -> bool;
 
     /// Returns an Event builder for the ethereum event represented by this types ABI signature.
-    fn new<M: Middleware>(filter: Filter, provider: &M) -> Event<M, Self>
+    fn new<B, M>(filter: Filter, provider: B) -> Event<B, M, Self>
     where
         Self: Sized,
+        B: Borrow<M>,
+        M: Middleware,
     {
         let filter = filter.event(&Self::abi_signature());
-        Event { filter, provider, datatype: PhantomData }
+        Event { filter, provider, datatype: PhantomData, _m: PhantomData }
     }
 }
 
@@ -53,16 +66,22 @@ impl<T: EthEvent> EthLogDecode for T {
 /// Helper for managing the event filter before querying or streaming its logs
 #[derive(Debug)]
 #[must_use = "event filters do nothing unless you `query` or `stream` them"]
-pub struct Event<'a, M, D> {
+pub struct Event<B, M, D> {
     /// The event filter's state
     pub filter: Filter,
-    pub(crate) provider: &'a M,
+    pub(crate) provider: B,
     /// Stores the event datatype
     pub(crate) datatype: PhantomData<D>,
+    pub(crate) _m: PhantomData<M>,
 }
 
 // TODO: Improve these functions
-impl<M, D: EthLogDecode> Event<'_, M, D> {
+impl<B, M, D> Event<B, M, D>
+where
+    B: Borrow<M>,
+    M: Middleware,
+    D: EthLogDecode,
+{
     /// Sets the filter's `from` block
     #[allow(clippy::wrong_self_convention)]
     pub fn from_block<T: Into<BlockNumber>>(mut self, block: T) -> Self {
@@ -116,8 +135,9 @@ impl<M, D: EthLogDecode> Event<'_, M, D> {
     }
 }
 
-impl<'a, M, D> Event<'a, M, D>
+impl<B, M, D> Event<B, M, D>
 where
+    B: Borrow<M>,
     M: Middleware,
     D: EthLogDecode,
 {
@@ -161,40 +181,49 @@ where
     /// # }
     /// ```
     pub async fn stream(
-        &'a self,
+        &self,
     ) -> Result<
         // Wraps the FilterWatcher with a mapping to the event
-        EventStream<'a, FilterWatcher<'a, M::Provider, Log>, D, ContractError<M>>,
+        EventStream<'_, FilterWatcher<'_, M::Provider, Log>, D, 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| self.parse_log(log))))
+        let filter = self
+            .provider
+            .borrow()
+            .watch(&self.filter)
+            .await
+            .map_err(ContractError::MiddlewareError)?;
+        Ok(EventStream::new(filter.id, filter, Box::new(move |log| Ok(parse_log(log)?))))
     }
 
     /// As [`Self::stream`], but does not discard [`Log`] metadata.
     pub async fn stream_with_meta(
-        &'a self,
+        &self,
     ) -> Result<
         // Wraps the FilterWatcher with a mapping to the event
-        EventStream<'a, FilterWatcher<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
+        EventStream<'_, FilterWatcher<'_, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
         ContractError<M>,
     > {
-        let filter =
-            self.provider.watch(&self.filter).await.map_err(ContractError::MiddlewareError)?;
+        let filter = self
+            .provider
+            .borrow()
+            .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))
+                Ok((parse_log(log)?, meta))
             }),
         ))
     }
 }
 
-impl<'a, M, D> Event<'a, M, D>
+impl<B, M, D> Event<B, M, D>
 where
+    B: Borrow<M>,
     M: Middleware,
     <M as Middleware>::Provider: PubsubClient,
     D: EthLogDecode,
@@ -203,29 +232,31 @@ where
     ///
     /// See also [Self::stream()].
     pub async fn subscribe(
-        &'a self,
+        &self,
     ) -> Result<
         // Wraps the SubscriptionStream with a mapping to the event
-        EventStream<'a, SubscriptionStream<'a, M::Provider, Log>, D, ContractError<M>>,
+        EventStream<'_, SubscriptionStream<'_, M::Provider, Log>, D, ContractError<M>>,
         ContractError<M>,
     > {
         let filter = self
             .provider
+            .borrow()
             .subscribe_logs(&self.filter)
             .await
             .map_err(ContractError::MiddlewareError)?;
-        Ok(EventStream::new(filter.id, filter, Box::new(move |log| self.parse_log(log))))
+        Ok(EventStream::new(filter.id, filter, Box::new(move |log| Ok(parse_log(log)?))))
     }
 
     pub async fn subscribe_with_meta(
-        &'a self,
+        &self,
     ) -> Result<
         // Wraps the SubscriptionStream with a mapping to the event
-        EventStream<'a, SubscriptionStream<'a, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
+        EventStream<'_, SubscriptionStream<'_, M::Provider, Log>, (D, LogMeta), ContractError<M>>,
         ContractError<M>,
     > {
         let filter = self
             .provider
+            .borrow()
             .subscribe_logs(&self.filter)
             .await
             .map_err(ContractError::MiddlewareError)?;
@@ -234,25 +265,30 @@ where
             filter,
             Box::new(move |log| {
                 let meta = LogMeta::from(&log);
-                Ok((self.parse_log(log)?, meta))
+                Ok((parse_log(log)?, meta))
             }),
         ))
     }
 }
 
-impl<M, D> Event<'_, M, D>
+impl<B, M, D> Event<B, M, D>
 where
+    B: Borrow<M>,
     M: Middleware,
     D: EthLogDecode,
 {
     /// Queries the blockchain for the selected filter and returns a vector of matching
     /// event logs
     pub async fn query(&self) -> Result<Vec<D>, ContractError<M>> {
-        let logs =
-            self.provider.get_logs(&self.filter).await.map_err(ContractError::MiddlewareError)?;
+        let logs = self
+            .provider
+            .borrow()
+            .get_logs(&self.filter)
+            .await
+            .map_err(ContractError::MiddlewareError)?;
         let events = logs
             .into_iter()
-            .map(|log| self.parse_log(log))
+            .map(|log| Ok(parse_log(log)?))
             .collect::<Result<Vec<_>, ContractError<M>>>()?;
         Ok(events)
     }
@@ -260,20 +296,20 @@ where
     /// Queries the blockchain for the selected filter and returns a vector of logs
     /// along with their metadata
     pub async fn query_with_meta(&self) -> Result<Vec<(D, LogMeta)>, ContractError<M>> {
-        let logs =
-            self.provider.get_logs(&self.filter).await.map_err(ContractError::MiddlewareError)?;
+        let logs = self
+            .provider
+            .borrow()
+            .get_logs(&self.filter)
+            .await
+            .map_err(ContractError::MiddlewareError)?;
         let events = logs
             .into_iter()
             .map(|log| {
                 let meta = LogMeta::from(&log);
-                let event = self.parse_log(log)?;
+                let event = parse_log(log)?;
                 Ok((event, meta))
             })
             .collect::<Result<_, ContractError<M>>>()?;
         Ok(events)
     }
-
-    pub fn parse_log(&self, log: Log) -> Result<D, ContractError<M>> {
-        D::decode_log(&RawLog { topics: log.topics, data: log.data.to_vec() }).map_err(From::from)
-    }
 }
diff --git a/ethers-middleware/src/transformer/ds_proxy/factory.rs b/ethers-middleware/src/transformer/ds_proxy/factory.rs
index 71d35043..665d5059 100644
--- a/ethers-middleware/src/transformer/ds_proxy/factory.rs
+++ b/ethers-middleware/src/transformer/ds_proxy/factory.rs
@@ -98,13 +98,13 @@ mod dsproxyfactory_mod {
                 .expect("method not found (this should never happen)")
         }
         ///Gets the contract's `Created` event
-        pub fn created_filter(&self) -> Event<M, CreatedFilter> {
+        pub fn created_filter(&self) -> Event<Arc<M>, M, CreatedFilter> {
             self.0.event()
         }
 
         /// Returns an [`Event`](ethers_contract::builders::Event) builder for all events of this
         /// contract
-        pub fn events(&self) -> Event<M, CreatedFilter> {
+        pub fn events(&self) -> Event<Arc<M>, M, CreatedFilter> {
             self.0.event_with_filter(Default::default())
         }
     }
diff --git a/examples/subscriptions/examples/subscribe_events_by_type.rs b/examples/subscriptions/examples/subscribe_events_by_type.rs
index 355404a3..8f935c0b 100644
--- a/examples/subscriptions/examples/subscribe_events_by_type.rs
+++ b/examples/subscriptions/examples/subscribe_events_by_type.rs
@@ -26,7 +26,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     // Build an Event by type. We are not tied to a contract instance. We use builder functions to
     // refine the event filter
-    let event = Contract::event_of_type::<AnswerUpdatedFilter>(&client)
+    let event = Contract::event_of_type::<AnswerUpdatedFilter>(client)
         .from_block(16022082)
         .address(ValueOrArray::Array(vec![
             PRICE_FEED_1.parse()?,


Test patch:
diff --git a/ethers-contract/tests/it/contract.rs b/ethers-contract/tests/it/contract.rs
index 0d3b7a64..b5e85b03 100644
--- a/ethers-contract/tests/it/contract.rs
+++ b/ethers-contract/tests/it/contract.rs
@@ -410,7 +410,7 @@ mod eth_tests {
 
         let anvil = Anvil::new().spawn();
         let client = connect(&anvil, 0);
-        let event = ethers_contract::Contract::event_of_type::<AnswerUpdatedFilter>(&client);
+        let event = ethers_contract::Contract::event_of_type::<AnswerUpdatedFilter>(client);
         assert_eq!(event.filter, Filter::new().event(&AnswerUpdatedFilter::abi_signature()));
     }