EIP-7732: Refactor Beacon chain state transition function (#3898)

specs/_features/eip7732/beacon-chain.md

@@ -50,10 +50,11 @@
  - [Modified `process_operations`](#modified-process_operations)
  - [Payload Attestations](#payload-attestations)
  - [`process_payload_attestation`](#process_payload_attestation)
- - [Modified `process_execution_payload`](#modified-process_execution_payload)
- - [New `verify_execution_payload_envelope_signature`](#new-verify_execution_payload_envelope_signature)
  - [Modified `is_merge_transition_complete`](#modified-is_merge_transition_complete)
  - [Modified `validate_merge_block`](#modified-validate_merge_block)
+ - [Execution payload processing](#execution-payload-processing)
+ - [New `verify_execution_payload_envelope_signature`](#new-verify_execution_payload_envelope_signature)
+ - [New `process_execution_payload`](#new-process_execution_payload)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -429,7 +430,8 @@ The post-state corresponding to a pre-state `state` and a signed execution paylo
 def process_block(state: BeaconState, block: BeaconBlock) -> None:
  process_block_header(state, block)
  process_withdrawals(state) # [Modified in EIP-7732]
- process_execution_payload_header(state, block) # [Modified in EIP-7732, removed process_execution_payload]
+ # Removed `process_execution_payload` in EIP-7732
+ process_execution_payload_header(state, block) # [New in EIP-7732]
  process_randao(state, block.body)
  process_eth1_data(state, block.body)
  process_operations(state, block.body) # [Modified in EIP-7732]
@@ -597,9 +599,51 @@ def process_payload_attestation(state: BeaconState, payload_attestation: Payload
  increase_balance(state, proposer_index, proposer_reward)
 ```
 
-#### Modified `process_execution_payload`
+#### Modified `is_merge_transition_complete`
+
+`is_merge_transition_complete` is modified only for testing purposes to add the blob kzg commitments root for an empty list
+
+```python
+def is_merge_transition_complete(state: BeaconState) -> bool:
+ header = ExecutionPayloadHeader()
+ kzgs = List[KZGCommitment, MAX_BLOB_COMMITMENTS_PER_BLOCK]()
+ header.blob_kzg_commitments_root = kzgs.hash_tree_root()
+
+ return state.latest_execution_payload_header != header
+```
 
-##### New `verify_execution_payload_envelope_signature`
+#### Modified `validate_merge_block`
+`validate_merge_block` is modified to use the new `signed_execution_payload_header` message in the Beacon Block Body
+
+```python
+def validate_merge_block(block: BeaconBlock) -> None:
+ """
+ Check the parent PoW block of execution payload is a valid terminal PoW block.
+
+ Note: Unavailable PoW block(s) may later become available,
+ and a client software MAY delay a call to ``validate_merge_block``
+ until the PoW block(s) become available.
+ """
+ if TERMINAL_BLOCK_HASH != Hash32():
+ # If `TERMINAL_BLOCK_HASH` is used as an override, the activation epoch must be reached.
+ assert compute_epoch_at_slot(block.slot) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
+ assert block.body.signed_execution_payload_header.message.parent_block_hash == TERMINAL_BLOCK_HASH
+ return
+
+ # Modified in EIP-7732
+ pow_block = get_pow_block(block.body.signed_execution_payload_header.message.parent_block_hash)
+ # Check if `pow_block` is available
+ assert pow_block is not None
+ pow_parent = get_pow_block(pow_block.parent_hash)
+ # Check if `pow_parent` is available
+ assert pow_parent is not None
+ # Check if `pow_block` is a valid terminal PoW block
+ assert is_valid_terminal_pow_block(pow_block, pow_parent)
+```
+
+### Execution payload processing
+
+#### New `verify_execution_payload_envelope_signature`
 
 ```python
 def verify_execution_payload_envelope_signature(
@@ -609,6 +653,8 @@ def verify_execution_payload_envelope_signature(
  return bls.Verify(builder.pubkey, signing_root, signed_envelope.signature)
 ```
 
+#### New `process_execution_payload`
+
 *Note*: `process_execution_payload` is now an independent check in state transition. It is called when importing a signed execution payload proposed by the builder of the current slot.
 
 ```python
@@ -679,45 +725,3 @@ def process_execution_payload(state: BeaconState,
  if verify: 
  assert envelope.state_root == hash_tree_root(state)
 ```
-
-#### Modified `is_merge_transition_complete`
-
-`is_merge_transition_complete` is modified only for testing purposes to add the blob kzg commitments root for an empty list
-
-```python
-def is_merge_transition_complete(state: BeaconState) -> bool:
- header = ExecutionPayloadHeader()
- kzgs = List[KZGCommitment, MAX_BLOB_COMMITMENTS_PER_BLOCK]()
- header.blob_kzg_commitments_root = kzgs.hash_tree_root()
-
- return state.latest_execution_payload_header != header
-```
-
-#### Modified `validate_merge_block`
-`validate_merge_block` is modified to use the new `signed_execution_payload_header` message in the Beacon Block Body
-
-```python
-def validate_merge_block(block: BeaconBlock) -> None:
- """
- Check the parent PoW block of execution payload is a valid terminal PoW block.
-
- Note: Unavailable PoW block(s) may later become available,
- and a client software MAY delay a call to ``validate_merge_block``
- until the PoW block(s) become available.
- """
- if TERMINAL_BLOCK_HASH != Hash32():
- # If `TERMINAL_BLOCK_HASH` is used as an override, the activation epoch must be reached.
- assert compute_epoch_at_slot(block.slot) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
- assert block.body.signed_execution_payload_header.message.parent_block_hash == TERMINAL_BLOCK_HASH
- return
-
- # Modified in EIP-7732
- pow_block = get_pow_block(block.body.signed_execution_payload_header.message.parent_block_hash)
- # Check if `pow_block` is available
- assert pow_block is not None
- pow_parent = get_pow_block(pow_block.parent_hash)
- # Check if `pow_parent` is available
- assert pow_parent is not None
- # Check if `pow_block` is a valid terminal PoW block
- assert is_valid_terminal_pow_block(pow_block, pow_parent)
-```