Merge pull request #2760 from ethereum/fix-proposer-boost-apply

Apply proposer boost to ancestors correctly

specs/phase0/fork-choice.md

@@ -181,8 +181,14 @@ def get_latest_attesting_balance(store: Store, root: Root) -> Gwei:
         if (i in store.latest_messages
             and get_ancestor(store, store.latest_messages[i].root, store.blocks[root].slot) == root)
     ))
+    if store.proposer_boost_root == Root():
+        # Return only attestation score if ``proposer_boost_root`` is not set
+        return attestation_score
+
+    # Calculate proposer score if ``proposer_boost_root`` is set
     proposer_score = Gwei(0)
-    if store.proposer_boost_root != Root() and root == store.proposer_boost_root:
+    # Boost is applied if ``root`` is an ancestor of ``proposer_boost_root``
+    if get_ancestor(store, store.proposer_boost_root, store.blocks[root].slot) == root:
         num_validators = len(get_active_validator_indices(state, get_current_epoch(state)))
         avg_balance = get_total_active_balance(state) // num_validators
         committee_size = num_validators // SLOTS_PER_EPOCH

tests/core/pyspec/eth2spec/test/phase0/fork_choice/test_get_head.py

@@ -166,6 +166,9 @@ def test_shorter_chain_but_heavier_weight(spec, state):
     signed_short_block = state_transition_and_sign_block(spec, short_state, short_block)
     yield from tick_and_add_block(spec, store, signed_short_block, test_steps)
 
+    # Since the long chain has higher proposer_score at slot 1, the latest long block is the head
+    assert spec.get_head(store) == spec.hash_tree_root(long_block)
+
     short_attestation = get_valid_attestation(spec, short_state, short_block.slot, signed=True)
     yield from tick_and_run_on_attestation(spec, store, short_attestation, test_steps)