Use slot from header instead of bid (#5554)

On Discord, @potuz suggested we use the slot from
`state.latest_block_header` instead of
`state.latest_execution_payload_bid`. This is a bit simpler, as we do
not need to cache the parent slot in `process_execution_payload_bid`.

Author: jtraglia

specs/_features/eip8148/beacon-chain.md

@@ -498,7 +498,7 @@ def apply_parent_execution_payload(
     requests: ExecutionRequests,
 ) -> None:
     parent_bid = state.latest_execution_payload_bid
-    parent_slot = parent_bid.slot
+    parent_slot = state.latest_block_header.slot
     parent_epoch = compute_epoch_at_slot(parent_slot)
 
     assert len(requests.withdrawals) <= MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD

specs/gloas/beacon-chain.md

@@ -1697,6 +1697,9 @@ def process_ptc_window(state: BeaconState) -> None:
 
 ```python
 def process_block(state: BeaconState, block: BeaconBlock) -> None:
+    # [New in Gloas:EIP7732]
+    parent_slot = state.latest_block_header.slot
+
     # [New in Gloas:EIP7732]
     process_parent_execution_payload(state, block)
     process_block_header(state, block)
@@ -1705,7 +1708,7 @@ def process_block(state: BeaconState, block: BeaconBlock) -> None:
     # [Modified in Gloas:EIP7732]
     # Removed `process_execution_payload`
     # [New in Gloas:EIP7732]
-    parent_slot = process_execution_payload_bid(state, block.body.signed_execution_payload_bid)
+    process_execution_payload_bid(state, block.body.signed_execution_payload_bid)
     process_randao(state, block.body)
     process_eth1_data(state, block.body)
     # [Modified in Gloas:EIP7732]
@@ -1728,7 +1731,7 @@ def apply_parent_execution_payload(
     requests: ExecutionRequests,
 ) -> None:
     parent_bid = state.latest_execution_payload_bid
-    parent_slot = parent_bid.slot
+    parent_slot = state.latest_block_header.slot
     parent_epoch = compute_epoch_at_slot(parent_slot)
 
     assert len(requests.withdrawals) <= MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD
@@ -2080,14 +2083,10 @@ def verify_execution_payload_bid_signature(
 
 ##### New `process_execution_payload_bid`
 
-*Note*: This function returns the slot of the parent block, read from the bid in
-the state before it is overwritten by the new bid. The slot is later given to
-`process_attestation` to look up the payload availability of the attested block.
-
 ```python
 def process_execution_payload_bid(
     state: BeaconState, signed_bid: SignedExecutionPayloadBid
-) -> Slot:
+) -> None:
     bid = signed_bid.message
     builder_index = bid.builder_index
     amount = bid.value
@@ -2135,13 +2134,8 @@ def process_execution_payload_bid(
             pending_payment
         )
 
-    # Cache the parent block's slot before overwriting the bid
-    parent_slot = state.latest_execution_payload_bid.slot
-
     # Cache the signed execution payload bid
     state.latest_execution_payload_bid = bid
-
-    return parent_slot
 ```
 
 #### Operations

tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_attestation.py

@@ -502,7 +502,7 @@ def test_old_attested_block_gets_head_flag(spec, state):
         state, attestation_slot
     )
     # The genesis payload was never revealed, which matches data.index == 0
-    parent_slot = state.latest_execution_payload_bid.slot
+    parent_slot = state.latest_block_header.slot
     assert parent_slot == 0
     assert not state.execution_payload_availability[parent_slot % spec.SLOTS_PER_HISTORICAL_ROOT]
 
@@ -545,7 +545,7 @@ def test_builder_payment_weight_tracking_previous_epoch(spec, state):
         state,
         attestation.data,
         state.slot - attestation.data.slot,
-        state.latest_execution_payload_bid.slot,
+        state.latest_block_header.slot,
     )
     pre_prev_flags = state.previous_epoch_participation[attester]
     pre_curr_flags = state.current_epoch_participation[attester]

tests/core/pyspec/eth_consensus_specs/test/gloas/block_processing/test_process_parent_execution_payload.py

@@ -51,7 +51,9 @@ def _commit_full_parent_with_payment(spec, state, value, builder_index, fee_reci
     Commit a FULL parent with a builder payment at slot ``SLOTS_PER_EPOCH - 1``.
     Clear its availability bit.
     """
-    state.latest_execution_payload_bid.slot = spec.Slot(spec.SLOTS_PER_EPOCH - 1)
+    parent_slot = spec.Slot(spec.SLOTS_PER_EPOCH - 1)
+    state.latest_block_header.slot = parent_slot
+    state.latest_execution_payload_bid.slot = parent_slot
     state.latest_execution_payload_bid.fee_recipient = fee_recipient
     _commit_parent_requests(
         spec, state, spec.ExecutionRequests(), value=value, builder_index=builder_index
@@ -94,7 +96,7 @@ def test_process_parent_execution_payload__empty_parent(spec, state):
     assert not is_parent_block_full
 
     pre_latest_block_hash = state.latest_block_hash
-    parent_slot = state.latest_execution_payload_bid.slot
+    parent_slot = state.latest_block_header.slot
     pre_availability = state.execution_payload_availability[
         parent_slot % spec.SLOTS_PER_HISTORICAL_ROOT
     ]

tests/core/pyspec/eth_consensus_specs/test/helpers/attestations.py

@@ -18,9 +18,7 @@
 
 
 def get_parent_slot(state):
-    # Outside of block processing, the bid in the state is still the
-    # parent block's bid, so its slot is the parent block's slot.
-    return state.latest_execution_payload_bid.slot
+    return state.latest_block_header.slot
 
 
 def process_attestation(spec, state, attestation):

tests/core/pyspec/eth_consensus_specs/test/phase0/sanity/test_blocks.py

@@ -165,6 +165,9 @@ def process_and_sign_block_without_header_validations(spec, state, block):
     WARNING UNSAFE: Only use when generating valid-looking invalid blocks for test vectors
     """
 
+    # Cache the parent slot before overwriting the header, as `process_block` does
+    parent_slot = state.latest_block_header.slot
+
     # Perform single mutation in `process_block_header`
     state.latest_block_header = spec.BeaconBlockHeader(
         slot=block.slot,
@@ -186,9 +189,7 @@ def process_and_sign_block_without_header_validations(spec, state, block):
     spec.process_randao(state, block.body)
     spec.process_eth1_data(state, block.body)
     if is_post_gloas(spec):
-        # The bid is not processed here, so the bid in the state is still
-        # the parent block's bid and its slot is the parent block's slot.
-        spec.process_operations(state, block.body, state.latest_execution_payload_bid.slot)
+        spec.process_operations(state, block.body, parent_slot)
     else:
         spec.process_operations(state, block.body)
     if is_post_altair(spec):