From 067dad79d27a66949f9bf9e6ee81d251f0290239 Mon Sep 17 00:00:00 2001
From: Matthias Seitz <matthias.seitz@outlook.de>
Date: Mon, 29 Jul 2024 15:13:23 +0200
Subject: [PATCH] feat: update backfill sync state to pending when we request
 it (#9865)

---
 crates/engine/tree/src/engine.rs   |  7 +++++++
 crates/engine/tree/src/tree/mod.rs | 20 ++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/crates/engine/tree/src/engine.rs b/crates/engine/tree/src/engine.rs
index bd4c220565..637bd5b944 100644
--- a/crates/engine/tree/src/engine.rs
+++ b/crates/engine/tree/src/engine.rs
@@ -216,6 +216,13 @@ pub enum EngineApiEvent {
     Download(DownloadRequest),
 }
 
+impl EngineApiEvent {
+    /// Returns `true` if the event is a backfill action.
+    pub const fn is_backfill_action(&self) -> bool {
+        matches!(self, Self::BackfillAction(_))
+    }
+}
+
 impl From<BeaconConsensusEngineEvent> for EngineApiEvent {
     fn from(event: BeaconConsensusEngineEvent) -> Self {
         Self::BeaconConsensus(event)
diff --git a/crates/engine/tree/src/tree/mod.rs b/crates/engine/tree/src/tree/mod.rs
index ece231d1ae..d9707f1467 100644
--- a/crates/engine/tree/src/tree/mod.rs
+++ b/crates/engine/tree/src/tree/mod.rs
@@ -635,14 +635,14 @@ where
     }
 
     /// Convenience function to handle an optional tree event.
-    fn on_maybe_tree_event(&self, event: Option<TreeEvent>) {
+    fn on_maybe_tree_event(&mut self, event: Option<TreeEvent>) {
         if let Some(event) = event {
             self.on_tree_event(event);
         }
     }
 
     /// Handles a tree event.
-    fn on_tree_event(&self, event: TreeEvent) {
+    fn on_tree_event(&mut self, event: TreeEvent) {
         match event {
             TreeEvent::TreeAction(action) => match action {
                 TreeAction::MakeCanonical(target) => {
@@ -659,10 +659,22 @@ where
     }
 
     /// Emits an outgoing event to the engine.
-    fn emit_event(&self, event: impl Into<EngineApiEvent>) {
+    fn emit_event(&mut self, event: impl Into<EngineApiEvent>) {
+        let event = event.into();
+
+        if event.is_backfill_action() {
+            debug_assert_eq!(
+                self.backfill_sync_state,
+                BackfillSyncState::Idle,
+                "backfill action should only be emitted when backfill is idle"
+            );
+            self.backfill_sync_state = BackfillSyncState::Pending;
+            debug!(target: "engine", "emitting backfill action event");
+        }
+
         let _ = self
             .outgoing
-            .send(event.into())
+            .send(event)
             .inspect_err(|err| error!("Failed to send internal event: {err:?}"));
     }