Exclude empty requests in requests list

specs/electra/beacon-chain.md

@@ -12,6 +12,7 @@
 - [Constants](#constants)
   - [Misc](#misc)
   - [Withdrawal prefixes](#withdrawal-prefixes)
+  - [Execution layer triggered requests](#execution-layer-triggered-requests)
 - [Preset](#preset)
   - [Gwei values](#gwei-values)
   - [Rewards and penalties](#rewards-and-penalties)
@@ -137,6 +138,14 @@ The following values are (non-configurable) constants used throughout the specif
 | - | - |
 | `COMPOUNDING_WITHDRAWAL_PREFIX` | `Bytes1('0x02')` |
 
+### Execution layer triggered requests
+
+| Name | Value |
+| - | - |
+| `DEPOSIT_REQUEST_TYPE` | `Bytes1('0x00')` |
+| `WITHDRAWAL_REQUEST_TYPE` | `Bytes1('0x01')` |
+| `CONSOLIDATION_REQUEST_TYPE` | `Bytes1('0x02')` |
+
 ## Preset
 
 ### Gwei values
@@ -1146,11 +1155,17 @@ def process_withdrawals(state: BeaconState, payload: ExecutionPayload) -> None:
 
 ```python
 def get_execution_requests_list(execution_requests: ExecutionRequests) -> Sequence[bytes]:
-    deposit_bytes = ssz_serialize(execution_requests.deposits)
-    withdrawal_bytes = ssz_serialize(execution_requests.withdrawals)
-    consolidation_bytes = ssz_serialize(execution_requests.consolidations)
-
-    return [deposit_bytes, withdrawal_bytes, consolidation_bytes]
+    requests = [
+        (DEPOSIT_REQUEST_TYPE, execution_requests.deposits),
+        (WITHDRAWAL_REQUEST_TYPE, execution_requests.withdrawals),
+        (CONSOLIDATION_REQUEST_TYPE, execution_requests.consolidations),
+    ]
+
+    return [
+        request_type + ssz_serialize(request_data)
+        for request_type, request_data in requests
+        if len(request_data) != 0
+    ]
 ```
 
 ##### Modified `process_execution_payload`

specs/electra/validator.md

@@ -189,18 +189,38 @@ def prepare_execution_payload(state: BeaconState,
 
 *[New in Electra]*
 
-1. The execution payload is obtained from the execution engine as defined above using `payload_id`. The response also includes a `execution_requests` entry containing a list of bytes. Each element on the list corresponds to one SSZ list of requests as defined
-in [EIP-7685](https://eips.ethereum.org/EIPS/eip-7685). The index of each element in the array determines the type of request.
+1. The execution payload is obtained from the execution engine as defined above using `payload_id`. The response also includes a `execution_requests` entry containing a list of bytes. Each element on the list corresponds to one SSZ list of requests as defined in [EIP-7685](https://eips.ethereum.org/EIPS/eip-7685). The first byte of each request is used to determine the request type. There can only be one instance of each request type per execution requests.
 2. Set `block.body.execution_requests = get_execution_requests(execution_requests)`, where:
 
 ```python
-def get_execution_requests(execution_requests: Sequence[bytes]) -> ExecutionRequests:
-    deposits = ssz_deserialize(List[DepositRequest, MAX_DEPOSIT_REQUESTS_PER_PAYLOAD], execution_requests[0])
-    withdrawals = ssz_deserialize(List[WithdrawalRequest, MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD], execution_requests[1])
-    consolidations = ssz_deserialize(List[ConsolidationRequest, MAX_CONSOLIDATION_REQUESTS_PER_PAYLOAD],
-                                     execution_requests[2])
-
-    return ExecutionRequests(deposits, withdrawals, consolidations)
+def get_execution_requests(execution_requests_list: Sequence[bytes]) -> ExecutionRequests:
+    requests = {
+        DEPOSIT_REQUEST_TYPE: {
+            "value": None,
+            "field": "deposits",
+            "type": List[DepositRequest, MAX_DEPOSIT_REQUESTS_PER_PAYLOAD],
+        },
+        WITHDRAWAL_REQUEST_TYPE: {
+            "value": None,
+            "field": "withdrawals",
+            "type": List[WithdrawalRequest, MAX_WITHDRAWAL_REQUESTS_PER_PAYLOAD],
+        },
+        CONSOLIDATION_REQUEST_TYPE: {
+            "value": None,
+            "field": "consolidations",
+            "type": List[ConsolidationRequest, MAX_CONSOLIDATION_REQUESTS_PER_PAYLOAD],
+        },
+    }
+
+    execution_requests = ExecutionRequests()
+    for request in execution_requests_list:
+        request_type, request_data = request[0:1], request[1:]
+        assert request_type in requests, "unexpected request type"
+        assert len(request_data) != 0, "empty request data"
+        assert requests[request_type]["value"] is None, "duplicate request"
+        requests[request_type]["value"] = ssz_deserialize(requests[request_type]["type"], request_data)
+        setattr(execution_requests, requests[request_type]["field"], requests[request_type]["value"])
+    return execution_requests
 ```
 
 ## Attesting

tests/core/pyspec/eth2spec/test/electra/unittests/test_execution_requests.py

@@ -0,0 +1,115 @@
+from eth2spec.test.context import (
+    single_phase,
+    spec_test,
+    with_electra_and_later,
+)
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_serialization_round_trip__empty(spec):
+    execution_requests = spec.ExecutionRequests()
+    serialized_execution_requests = spec.get_execution_requests_list(execution_requests)
+    deserialized_execution_requests = spec.get_execution_requests(serialized_execution_requests)
+    assert deserialized_execution_requests == execution_requests
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_serialization_round_trip__one_request(spec):
+    execution_requests = spec.ExecutionRequests(
+        deposits=[spec.DepositRequest()],
+    )
+    serialized_execution_requests = spec.get_execution_requests_list(execution_requests)
+    deserialized_execution_requests = spec.get_execution_requests(serialized_execution_requests)
+    assert deserialized_execution_requests == execution_requests
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_serialization_round_trip__multiple_requests(spec):
+    execution_requests = spec.ExecutionRequests(
+        deposits=[spec.DepositRequest()],
+        withdrawals=[spec.WithdrawalRequest()],
+        consolidations=[spec.ConsolidationRequest()],
+    )
+    serialized_execution_requests = spec.get_execution_requests_list(execution_requests)
+    deserialized_execution_requests = spec.get_execution_requests(serialized_execution_requests)
+    assert deserialized_execution_requests == execution_requests
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_serialization_round_trip__one_request_with_real_data(spec):
+    execution_requests = spec.ExecutionRequests(
+        deposits=[
+            spec.DepositRequest(
+                pubkey=spec.BLSPubkey(48 * "aa"),
+                withdrawal_credentials=spec.Bytes32(32 * "bb"),
+                amount=spec.Gwei(11111111),
+                signature=spec.BLSSignature(96 * "cc"),
+                index=spec.uint64(22222222),
+            ),
+        ]
+    )
+    serialized_execution_requests = spec.get_execution_requests_list(execution_requests)
+    deserialized_execution_requests = spec.get_execution_requests(serialized_execution_requests)
+    assert deserialized_execution_requests == execution_requests
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_deserialize__allow_out_of_order_requests(spec):
+    serialized_execution_requests = [
+        spec.WITHDRAWAL_REQUEST_TYPE + 76 * b"\x0a",
+        spec.DEPOSIT_REQUEST_TYPE + 192 * b"\x0b",
+    ]
+    assert int(serialized_execution_requests[0][0]) > int(serialized_execution_requests[1][0])
+    spec.get_execution_requests(serialized_execution_requests)
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_deserialize__reject_empty_request(spec):
+    serialized_execution_requests = [b"\x01"]
+    try:
+        spec.get_execution_requests(serialized_execution_requests)
+        assert False, "expected exception"
+    except Exception as e:
+        assert "empty request data" in str(e)
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_deserialize__reject_duplicate_request(spec):
+    serialized_withdrawal = 76 * b"\x0a"
+    serialized_execution_requests = [
+        spec.WITHDRAWAL_REQUEST_TYPE + serialized_withdrawal,
+        spec.WITHDRAWAL_REQUEST_TYPE + serialized_withdrawal,
+    ]
+    try:
+        spec.get_execution_requests(serialized_execution_requests)
+        assert False, "expected exception"
+    except Exception as e:
+        assert "duplicate request" in str(e)
+
+
+@with_electra_and_later
+@spec_test
+@single_phase
+def test_requests_deserialize__reject_unexpected_request_type(spec):
+    serialized_execution_requests = [
+        b"\x03\xff\xff\xff",
+    ]
+    try:
+        spec.get_execution_requests(serialized_execution_requests)
+        assert False, "expected exception"
+    except Exception as e:
+        assert "unexpected request type" in str(e)