Fork choice: get proposer head

[mehdi-aouadi]

Modified get_proposer_head

The implementation of get_proposer_head is modified to also account for store.unsatisfied_inclusion_list_blocks.

def get_proposer_head(store: Store, head_root: Root, slot: Slot) -> Root:
    head_block = store.blocks[head_root]
    parent_root = head_block.parent_root
    parent_block = store.blocks[parent_root]

    # Only re-org the head block if it arrived later than the attestation deadline.
    head_late = is_head_late(store, head_root)

    # Do not re-org on an epoch boundary where the proposer shuffling could change.
    shuffling_stable = is_shuffling_stable(slot)

    # Ensure that the FFG information of the new head will be competitive with the current head.
    ffg_competitive = is_ffg_competitive(store, head_root, parent_root)

    # Do not re-org if the chain is not finalizing with acceptable frequency.
    finalization_ok = is_finalization_ok(store, slot)

    # Only re-org if we are proposing on-time.
    proposing_on_time = is_proposing_on_time(store)

    # Only re-org a single slot at most.
    parent_slot_ok = parent_block.slot + 1 == head_block.slot
    current_time_ok = head_block.slot + 1 == slot
    single_slot_reorg = parent_slot_ok and current_time_ok

    # Check that the head has few enough votes to be overpowered by our proposer boost.
    assert store.proposer_boost_root != head_root  # ensure boost has worn off
    head_weak = is_head_weak(store, head_root)

    # Check that the missing votes are assigned to the parent and not being hoarded.
    parent_strong = is_parent_strong(store, parent_root)


    reorg_prerequisites = all([shuffling_stable, ffg_competitive, finalization_ok,
                           proposing_on_time, single_slot_reorg, head_weak, parent_strong])

    # Check that the head block is in the unsatisfied inclusion list blocks
    inclusion_list_not_satisfied = head_root in store.unsatisfied_inclusion_list_blocks  # [New in EIP-7805]

    if reorg_prerequisites and (head_late or inclusion_list_not_satisfied):
        return parent_root
    else:
        return head_root