`get_paginated_logs` fixes and refactoring (#1328)

* fix(providers): do not load boundry blocks on every page

* refactor(providers): make get_paginated_logs TryStream

ethers-providers/src/log_query.rs

@@ -1,4 +1,4 @@
-use super::{JsonRpcClient, Middleware, PinBoxFut, Provider};
+use super::{JsonRpcClient, Middleware, PinBoxFut, Provider, ProviderError};
 use ethers_core::types::{Filter, Log, U64};
 use futures_core::stream::Stream;
 use std::{
@@ -6,6 +6,7 @@ use std::{
     pin::Pin,
     task::{Context, Poll},
 };
+use thiserror::Error;
 
 pub struct LogQuery<'a, P> {
     provider: &'a Provider<P>,
@@ -55,11 +56,19 @@ macro_rules! rewake_with_new_state {
     };
 }
 
+#[derive(Error, Debug)]
+pub enum LogQueryError<E> {
+    #[error(transparent)]
+    LoadLastBlockError(E),
+    #[error(transparent)]
+    LoadLogsError(E),
+}
+
 impl<'a, P> Stream for LogQuery<'a, P>
 where
     P: JsonRpcClient,
 {
-    type Item = Log;
+    type Item = Result<Log, LogQueryError<ProviderError>>;
 
     fn poll_next(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         match &mut self.state {
@@ -77,14 +86,15 @@ where
                 }
             }
             LogQueryState::LoadLastBlock(fut) => {
-                self.last_block = Some(
-                    futures_util::ready!(fut.as_mut().poll(ctx))
-                        .expect("error occurred loading last block"),
-                );
+                match futures_util::ready!(fut.as_mut().poll(ctx)) {
+                    Ok(last_block) => {
+                        self.last_block = Some(last_block);
 
+                        // this is okay because we will only enter this state when the filter is
+                        // paginatable i.e. from block is set
                         let from_block = self.filter.get_from_block().unwrap();
                         let to_block = from_block + self.page_size;
-                self.from_block = Some(to_block);
+                        self.from_block = Some(to_block + 1);
 
                         let filter = self.filter.clone().from_block(from_block).to_block(to_block);
                         let provider = self.provider;
@@ -92,12 +102,16 @@ where
                         let fut = Box::pin(async move { provider.get_logs(&filter).await });
                         rewake_with_new_state!(ctx, self, LogQueryState::LoadLogs(fut));
                     }
-            LogQueryState::LoadLogs(fut) => {
-                let logs = futures_util::ready!(fut.as_mut().poll(ctx))
-                    .expect("error occurred loading logs");
+                    Err(err) => Poll::Ready(Some(Err(LogQueryError::LoadLastBlockError(err)))),
+                }
+            }
+            LogQueryState::LoadLogs(fut) => match futures_util::ready!(fut.as_mut().poll(ctx)) {
+                Ok(logs) => {
                     self.current_logs = VecDeque::from(logs);
                     rewake_with_new_state!(ctx, self, LogQueryState::Consume);
                 }
+                Err(err) => Poll::Ready(Some(Err(LogQueryError::LoadLogsError(err)))),
+            },
             LogQueryState::Consume => {
                 let log = self.current_logs.pop_front();
                 if log.is_none() {
@@ -106,15 +120,17 @@ where
                         Poll::Ready(None)
                     } else {
                         // load new logs if there are still more pages to go through
+                        // can safely assume this will always be set in this state
                         let from_block = self.from_block.unwrap();
                         let to_block = from_block + self.page_size;
 
                         // no more pages to load, and everything is consumed
+                        // can safely assume this will always be set in this state
                         if from_block > self.last_block.unwrap() {
                             return Poll::Ready(None)
                         }
                         // load next page
-                        self.from_block = Some(to_block);
+                        self.from_block = Some(to_block + 1);
 
                         let filter = self.filter.clone().from_block(from_block).to_block(to_block);
                         let provider = self.provider;
@@ -122,7 +138,7 @@ where
                         rewake_with_new_state!(ctx, self, LogQueryState::LoadLogs(fut));
                     }
                 } else {
-                    Poll::Ready(log)
+                    Poll::Ready(log.map(Ok))
                 }
             }
         }

examples/paginated_logs.rs

@@ -1,10 +1,10 @@
-use ethers::{abi::AbiDecode, prelude::*, utils::keccak256};
+use ethers::{abi::AbiDecode, prelude::*, providers::Middleware, utils::keccak256};
 use eyre::Result;
 use std::sync::Arc;
 
 #[tokio::main]
 async fn main() -> Result<()> {
-    let client =
+    let client: Provider<Ws> =
         Provider::<Ws>::connect("wss://mainnet.infura.io/ws/v3/c60b0bb42f8a4c6481ecd229eddaca27")
             .await?;
     let client = Arc::new(client);
@@ -18,7 +18,8 @@ async fn main() -> Result<()> {
 
     let mut stream = client.get_logs_paginated(&erc20_transfer_filter, 10);
 
-    while let Some(log) = stream.next().await {
+    while let Some(res) = stream.next().await {
+        let log = res?;
         println!(
             "block: {:?}, tx: {:?}, token: {:?}, from: {:?}, to: {:?}, amount: {:?}",
             log.block_number,