fix(engine, pruner): prune poll logic, history indices (#4043)

crates/consensus/beacon/src/engine/forkchoice.rs

@@ -51,6 +51,18 @@ impl ForkchoiceStateTracker {
         self.latest_status().map(|s| s.is_valid()).unwrap_or(false)
     }
 
+    /// Returns whether the latest received FCU is syncing: [ForkchoiceStatus::Syncing]
+    #[allow(unused)]
+    pub(crate) fn is_latest_syncing(&self) -> bool {
+        self.latest_status().map(|s| s.is_syncing()).unwrap_or(false)
+    }
+
+    /// Returns whether the latest received FCU is syncing: [ForkchoiceStatus::Invalid]
+    #[allow(unused)]
+    pub(crate) fn is_latest_invalid(&self) -> bool {
+        self.latest_status().map(|s| s.is_invalid()).unwrap_or(false)
+    }
+
     /// Returns the last valid head hash.
     #[allow(unused)]
     pub(crate) fn last_valid_head(&self) -> Option<H256> {
@@ -98,6 +110,10 @@ impl ForkchoiceStatus {
         matches!(self, ForkchoiceStatus::Valid)
     }
 
+    pub(crate) fn is_invalid(&self) -> bool {
+        matches!(self, ForkchoiceStatus::Invalid)
+    }
+
     pub(crate) fn is_syncing(&self) -> bool {
         matches!(self, ForkchoiceStatus::Syncing)
     }

crates/consensus/beacon/src/engine/mod.rs

@@ -1715,12 +1715,13 @@ where
 
             // Poll prune controller if all conditions are met:
             // 1. Pipeline is idle
-            // 2. Pruning is running and we need to prioritize checking its events OR no engine and
-            //  sync messages are pending and we may start pruning
-            // 3. Latest FCU status is VALID
+            // 2. Either of two:
+            //  1. Pruning is running and we need to prioritize checking its events
+            //  2. Both engine and sync messages are pending AND latest FCU status is not INVALID,
+            //     so we may start pruning
             if this.sync.is_pipeline_idle() &&
-                (this.is_prune_active() || is_pending) &&
-                this.forkchoice_state_tracker.is_latest_valid()
+                (this.is_prune_active() ||
+                    is_pending && !this.forkchoice_state_tracker.is_latest_invalid())
             {
                 if let Some(ref mut prune) = this.prune {
                     match prune.poll(cx, this.blockchain.canonical_tip().number) {