Gloas ensure we emit payload attributes SSE event (#9348)

https://github.com/sigp/lighthouse/issues/8817

we were not emitting payload attribute SSE events for gloas. Since the head snapshot stores the canonical latest execution payload envelope we have all the info we need to emit the event.


  


Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Eitan Seri-Levi <eserilev@gmail.com>

beacon_node/beacon_chain/tests/prepare_payload.rs

@@ -689,3 +689,53 @@ async fn gloas_block_production_caches_blobs_for_column_publishing() {
         "Envelope should remain in cache after taking blobs"
     );
 }
+
+/// A Gloas proposer re-orging must use the parent's `prev_randao`
+#[tokio::test]
+async fn gloas_pre_payload_attributes_reorg_uses_parent_randao() {
+    let spec = Arc::new(test_spec::<E>());
+    if !spec.fork_name_at_slot::<E>(Slot::new(0)).gloas_enabled() {
+        return;
+    }
+
+    let db_path = tempdir().unwrap();
+    let store = get_store(&db_path, spec.clone());
+    let harness = get_harness(store.clone(), LOW_VALIDATOR_COUNT);
+
+    harness
+        .extend_chain(
+            5,
+            BlockStrategy::OnCanonicalHead,
+            AttestationStrategy::AllValidators,
+        )
+        .await;
+
+    let cached_head = harness.chain.canonical_head.cached_head();
+    let head_block_root = cached_head.head_block_root();
+    let head_parent_block_root = cached_head.parent_block_root();
+    let proposal_slot = cached_head.head_slot() + 1;
+
+    let head_random = cached_head.head_random().unwrap();
+    let parent_random = cached_head.parent_random().unwrap();
+    assert_ne!(head_random, parent_random);
+
+    let on_head = harness
+        .chain
+        .get_pre_payload_attributes(proposal_slot, head_block_root, &cached_head)
+        .unwrap()
+        .unwrap();
+    assert_eq!(on_head.prev_randao, head_random);
+
+    // value should always be none post gloas
+    assert_eq!(on_head.parent_block_number, None);
+
+    let on_parent = harness
+        .chain
+        .get_pre_payload_attributes(proposal_slot, head_parent_block_root, &cached_head)
+        .unwrap()
+        .unwrap();
+    assert_eq!(on_parent.prev_randao, parent_random);
+
+    // value should always be none post gloas
+    assert_eq!(on_parent.parent_block_number, None);
+}