Redefine initialize_beacon_state_from_eth1

specs/merge/beacon-chain.md

@@ -33,6 +33,7 @@
   - [Block processing](#block-processing)
     - [Execution payload processing](#execution-payload-processing)
       - [`process_execution_payload`](#process_execution_payload)
+- [Initialize state for pure Merge testnets and test vectors](#initialize-state-for-pure-merge-testnets-and-test-vectors)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 <!-- /TOC -->
@@ -233,3 +234,63 @@ def process_execution_payload(state: BeaconState,
         transactions_root=hash_tree_root(execution_payload.transactions),
     )
 ```
+
+## Initialize state for pure Merge testnets and test vectors
+
+This helper function is only for initializing the state for pure Merge testnets and tests.
+
+*Note*: The function `initialize_beacon_state_from_eth1` is modified: (1) using `MERGE_FORK_VERSION` as the current fork version, (2) utilizing the Merge `BeaconBlockBody` when constructing the initial `latest_block_header`, and (3) adding initial `latest_execution_payload_header`.
+
+```python
+def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
+                                      eth1_timestamp: uint64,
+                                      deposits: Sequence[Deposit]) -> BeaconState:
+    fork = Fork(
+        previous_version=GENESIS_FORK_VERSION,
+        current_version=MERGE_FORK_VERSION,  # [Modified in Merge]
+        epoch=GENESIS_EPOCH,
+    )
+    state = BeaconState(
+        genesis_time=eth1_timestamp + GENESIS_DELAY,
+        fork=fork,
+        eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
+        latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
+        randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR,  # Seed RANDAO with Eth1 entropy
+    )
+
+    # Process deposits
+    leaves = list(map(lambda deposit: deposit.data, deposits))
+    for index, deposit in enumerate(deposits):
+        deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
+        state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
+        process_deposit(state, deposit)
+
+    # Process activations
+    for index, validator in enumerate(state.validators):
+        balance = state.balances[index]
+        validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
+        if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
+            validator.activation_eligibility_epoch = GENESIS_EPOCH
+            validator.activation_epoch = GENESIS_EPOCH
+
+    # Set genesis validators root for domain separation and chain versioning
+    state.genesis_validators_root = hash_tree_root(state.validators)
+
+    # [New in Merge] Construct execution payload header
+    # Note: initialized with zero block height
+    state.latest_execution_payload_header = ExecutionPayloadHeader(
+        block_hash=eth1_block_hash,
+        parent_hash=Hash32(),
+        coinbase=Bytes20(),
+        state_root=Bytes32(),
+        number=uint64(0),
+        gas_limit=uint64(0),
+        gas_used=uint64(0),
+        timestamp=eth1_timestamp,
+        receipt_root=Bytes32(),
+        logs_bloom=ByteVector[BYTES_PER_LOGS_BLOOM](),
+        transactions_root=Root(),
+    )
+
+    return state
+```