fix: bad unwrap on resolve (#8675)

crates/payload/basic/src/lib.rs

@@ -180,7 +180,7 @@ where
 
         let cached_reads = self.maybe_pre_cached(config.parent_block.hash());
 
-        Ok(BasicPayloadJob {
+        let mut job = BasicPayloadJob {
             config,
             client: self.client.clone(),
             pool: self.pool.clone(),
@@ -193,7 +193,12 @@ where
             payload_task_guard: self.payload_task_guard.clone(),
             metrics: Default::default(),
             builder: self.builder.clone(),
-        })
+        };
+
+        // start the first job right away
+        job.spawn_build_job();
+
+        Ok(job)
     }
 
     fn on_new_state(&mut self, new_state: CanonStateNotification) {
@@ -347,6 +352,48 @@ where
     builder: Builder,
 }
 
+impl<Client, Pool, Tasks, Builder> BasicPayloadJob<Client, Pool, Tasks, Builder>
+where
+    Client: StateProviderFactory + Clone + Unpin + 'static,
+    Pool: TransactionPool + Unpin + 'static,
+    Tasks: TaskSpawner + Clone + 'static,
+    Builder: PayloadBuilder<Pool, Client> + Unpin + 'static,
+    <Builder as PayloadBuilder<Pool, Client>>::Attributes: Unpin + Clone,
+    <Builder as PayloadBuilder<Pool, Client>>::BuiltPayload: Unpin + Clone,
+{
+    /// Spawns a new payload build task.
+    fn spawn_build_job(&mut self) {
+        trace!(target: "payload_builder", "spawn new payload build task");
+        let (tx, rx) = oneshot::channel();
+        let client = self.client.clone();
+        let pool = self.pool.clone();
+        let cancel = Cancelled::default();
+        let _cancel = cancel.clone();
+        let guard = self.payload_task_guard.clone();
+        let payload_config = self.config.clone();
+        let best_payload = self.best_payload.clone();
+        self.metrics.inc_initiated_payload_builds();
+        let cached_reads = self.cached_reads.take().unwrap_or_default();
+        let builder = self.builder.clone();
+        self.executor.spawn_blocking(Box::pin(async move {
+            // acquire the permit for executing the task
+            let _permit = guard.acquire().await;
+            let args = BuildArguments {
+                client,
+                pool,
+                cached_reads,
+                config: payload_config,
+                cancel,
+                best_payload,
+            };
+            let result = builder.try_build(args);
+            let _ = tx.send(result);
+        }));
+
+        self.pending_block = Some(PendingPayload { _cancel, payload: rx });
+    }
+}
+
 impl<Client, Pool, Tasks, Builder> Future for BasicPayloadJob<Client, Pool, Tasks, Builder>
 where
     Client: StateProviderFactory + Clone + Unpin + 'static,
@@ -371,34 +418,7 @@ where
         while this.interval.poll_tick(cx).is_ready() {
             // start a new job if there is no pending block and we haven't reached the deadline
             if this.pending_block.is_none() {
-                trace!(target: "payload_builder", "spawn new payload build task");
-                let (tx, rx) = oneshot::channel();
-                let client = this.client.clone();
-                let pool = this.pool.clone();
-                let cancel = Cancelled::default();
-                let _cancel = cancel.clone();
-                let guard = this.payload_task_guard.clone();
-                let payload_config = this.config.clone();
-                let best_payload = this.best_payload.clone();
-                this.metrics.inc_initiated_payload_builds();
-                let cached_reads = this.cached_reads.take().unwrap_or_default();
-                let builder = this.builder.clone();
-                this.executor.spawn_blocking(Box::pin(async move {
-                    // acquire the permit for executing the task
-                    let _permit = guard.acquire().await;
-                    let args = BuildArguments {
-                        client,
-                        pool,
-                        cached_reads,
-                        config: payload_config,
-                        cancel,
-                        best_payload,
-                    };
-                    let result = builder.try_build(args);
-                    let _ = tx.send(result);
-                }));
-
-                this.pending_block = Some(PendingPayload { _cancel, payload: rx });
+                this.spawn_build_job();
             }
         }
 
@@ -470,6 +490,12 @@ where
 
     fn resolve(&mut self) -> (Self::ResolvePayloadFuture, KeepPayloadJobAlive) {
         let best_payload = self.best_payload.take();
+
+        if best_payload.is_none() && self.pending_block.is_none() {
+            // ensure we have a job scheduled if we don't have a best payload yet and none is active
+            self.spawn_build_job();
+        }
+
         let maybe_better = self.pending_block.take();
         let mut empty_payload = None;
 
@@ -539,10 +565,16 @@ pub struct ResolveBestPayload<Payload> {
     pub best_payload: Option<Payload>,
     /// Regular payload job that's currently running that might produce a better payload.
     pub maybe_better: Option<PendingPayload<Payload>>,
-    /// The empty payload building job in progress.
+    /// The empty payload building job in progress, if any.
     pub empty_payload: Option<oneshot::Receiver<Result<Payload, PayloadBuilderError>>>,
 }
 
+impl<Payload> ResolveBestPayload<Payload> {
+    const fn is_empty(&self) -> bool {
+        self.best_payload.is_none() && self.maybe_better.is_none() && self.empty_payload.is_none()
+    }
+}
+
 impl<Payload> Future for ResolveBestPayload<Payload>
 where
     Payload: Unpin,
@@ -568,9 +600,11 @@ where
             return Poll::Ready(Ok(best))
         }
 
-        let mut empty_payload = this.empty_payload.take().expect("polled after completion");
-        match empty_payload.poll_unpin(cx) {
-            Poll::Ready(Ok(res)) => {
+        if let Some(fut) = Pin::new(&mut this.empty_payload).as_pin_mut() {
+            if let Poll::Ready(res) = fut.poll(cx) {
+                this.empty_payload = None;
+                return match res {
+                    Ok(res) => {
                         if let Err(err) = &res {
                             warn!(target: "payload_builder", %err, "failed to resolve empty payload");
                         } else {
@@ -578,13 +612,17 @@ where
                         }
                         Poll::Ready(res)
                     }
-            Poll::Ready(Err(err)) => Poll::Ready(Err(err.into())),
-            Poll::Pending => {
-                this.empty_payload = Some(empty_payload);
+                    Err(err) => Poll::Ready(Err(err.into())),
+                }
+            }
+        }
+
+        if this.is_empty() {
+            return Poll::Ready(Err(PayloadBuilderError::MissingPayload))
+        }
+
         Poll::Pending
     }
-        }
-    }
 }
 
 /// A future that resolves to the result of the block building job.

crates/payload/builder/src/error.rs

@@ -14,6 +14,9 @@ pub enum PayloadBuilderError {
     /// An oneshot channels has been closed.
     #[error("sender has been dropped")]
     ChannelClosed,
+    /// If there's no payload to resolve.
+    #[error("missing payload")]
+    MissingPayload,
     /// Error occurring in the blob store.
     #[error(transparent)]
     BlobStore(#[from] BlobStoreError),