Sane SSZ object default values (#963)

specs/core/0_beacon-chain.md

@@ -51,7 +51,6 @@
         - [`hash`](#hash)
         - [`hash_tree_root`](#hash_tree_root)
         - [`signing_root`](#signing_root)
-        - [`get_temporary_block_header`](#get_temporary_block_header)
         - [`slot_to_epoch`](#slot_to_epoch)
         - [`get_previous_epoch`](#get_previous_epoch)
         - [`get_current_epoch`](#get_current_epoch)
@@ -201,13 +200,10 @@ These configurations are updated for releases, but may be out of sync during `de
 
 | Name | Value |
 | - | - |
-| `GENESIS_FORK_VERSION` | `int_to_bytes4(0)` |
 | `GENESIS_SLOT` | `0` |
 | `GENESIS_EPOCH` | `0` |
-| `GENESIS_START_SHARD` | `0` |
 | `FAR_FUTURE_EPOCH` | `2**64 - 1` |
 | `ZERO_HASH` | `int_to_bytes32(0)` |
-| `EMPTY_SIGNATURE` | `int_to_bytes96(0)` |
 | `BLS_WITHDRAWAL_PREFIX_BYTE` | `int_to_bytes1(0)` |
 
 ### Time parameters
@@ -640,23 +636,6 @@ Note: We aim to migrate to a S[T/N]ARK-friendly hash function in a future Ethere
 
 `def signing_root(object: SSZContainer) -> Bytes32` is a function defined in the [SimpleSerialize spec](../simple-serialize.md#self-signed-containers) to compute signing messages.
 
-### `get_temporary_block_header`
-
-```python
-def get_temporary_block_header(block: BeaconBlock) -> BeaconBlockHeader:
-    """
-    Return the block header corresponding to a block with ``state_root`` set to ``ZERO_HASH``.
-    """
-    return BeaconBlockHeader(
-        slot=block.slot,
-        previous_block_root=block.previous_block_root,
-        state_root=ZERO_HASH,
-        block_body_root=hash_tree_root(block.body),
-        # signing_root(block) is used for block id purposes so signature is a stub
-        signature=EMPTY_SIGNATURE,
-    )
-```
-
 ### `slot_to_epoch`
 
 ```python
@@ -1345,35 +1324,7 @@ When enough full deposits have been made to the deposit contract, an `Eth2Genesi
     * `genesis_eth1_data.deposit_count` is the `deposit_count` contained in the `Eth2Genesis` log.
     * `genesis_eth1_data.block_hash` is the hash of the Ethereum 1.0 block that emitted the `Eth2Genesis` log.
 * Let `genesis_state = get_genesis_beacon_state(genesis_validator_deposits, genesis_time, genesis_eth1_data)`.
-* Let `genesis_block = get_empty_block()`.
+* Let `genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))`.
-* Set `genesis_block.state_root = hash_tree_root(genesis_state)`.
-
-```python
-def get_empty_block() -> BeaconBlock:
-    """
-    Get an empty ``BeaconBlock``.
-    """
-    return BeaconBlock(
-        slot=GENESIS_SLOT,
-        previous_block_root=ZERO_HASH,
-        state_root=ZERO_HASH,
-        body=BeaconBlockBody(
-            randao_reveal=EMPTY_SIGNATURE,
-            eth1_data=Eth1Data(
-                deposit_root=ZERO_HASH,
-                deposit_count=0,
-                block_hash=ZERO_HASH,
-            ),
-            proposer_slashings=[],
-            attester_slashings=[],
-            attestations=[],
-            deposits=[],
-            voluntary_exits=[],
-            transfers=[],
-        ),
-        signature=EMPTY_SIGNATURE,
-    )
-```
 
 ```python
 def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
@@ -1382,50 +1333,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
     """
     Get the genesis ``BeaconState``.
     """
-    state = BeaconState(
+    state = BeaconState(genesis_time=genesis_time, latest_eth1_data=genesis_eth1_data)
-        # Misc
-        slot=GENESIS_SLOT,
-        genesis_time=genesis_time,
-        fork=Fork(
-            previous_version=GENESIS_FORK_VERSION,
-            current_version=GENESIS_FORK_VERSION,
-            epoch=GENESIS_EPOCH,
-        ),
-
-        # Validator registry
-        validator_registry=[],
-        balances=[],
-
-        # Randomness and committees
-        latest_randao_mixes=Vector([ZERO_HASH for _ in range(LATEST_RANDAO_MIXES_LENGTH)]),
-        latest_start_shard=GENESIS_START_SHARD,
-
-        # Finality
-        previous_epoch_attestations=[],
-        current_epoch_attestations=[],
-        previous_justified_epoch=GENESIS_EPOCH,
-        current_justified_epoch=GENESIS_EPOCH,
-        previous_justified_root=ZERO_HASH,
-        current_justified_root=ZERO_HASH,
-        justification_bitfield=0,
-        finalized_epoch=GENESIS_EPOCH,
-        finalized_root=ZERO_HASH,
-
-        # Recent state
-        current_crosslinks=Vector([Crosslink(epoch=GENESIS_EPOCH, previous_crosslink_root=ZERO_HASH, crosslink_data_root=ZERO_HASH) for _ in range(SHARD_COUNT)]),
-        previous_crosslinks=Vector([Crosslink(epoch=GENESIS_EPOCH, previous_crosslink_root=ZERO_HASH, crosslink_data_root=ZERO_HASH) for _ in range(SHARD_COUNT)]),
-        latest_block_roots=Vector([ZERO_HASH for _ in range(SLOTS_PER_HISTORICAL_ROOT)]),
-        latest_state_roots=Vector([ZERO_HASH for _ in range(SLOTS_PER_HISTORICAL_ROOT)]),
-        latest_active_index_roots=Vector([ZERO_HASH for _ in range(LATEST_ACTIVE_INDEX_ROOTS_LENGTH)]),
-        latest_slashed_balances=Vector([0 for _ in range(LATEST_SLASHED_EXIT_LENGTH)]),
-        latest_block_header=get_temporary_block_header(get_empty_block()),
-        historical_roots=[],
-
-        # Ethereum 1.0 chain data
-        latest_eth1_data=genesis_eth1_data,
-        eth1_data_votes=[],
-        deposit_index=0,
-    )
 
     # Process genesis deposits
     for deposit in genesis_validator_deposits:
@@ -1929,7 +1837,11 @@ def process_block_header(state: BeaconState, block: BeaconBlock) -> None:
     # Verify that the parent matches
     assert block.previous_block_root == signing_root(state.latest_block_header)
     # Save current block as the new latest block
-    state.latest_block_header = get_temporary_block_header(block)
+    state.latest_block_header = BeaconBlockHeader(
+        slot=block.slot,
+        previous_block_root=block.previous_block_root,
+        block_body_root=hash_tree_root(block.body),
+    )
     # Verify proposer is not slashed
     proposer = state.validator_registry[get_beacon_proposer_index(state)]
     assert not proposer.slashed
@@ -2132,8 +2044,6 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
             activation_epoch=FAR_FUTURE_EPOCH,
             exit_epoch=FAR_FUTURE_EPOCH,
             withdrawable_epoch=FAR_FUTURE_EPOCH,
-            slashed=False,
-            high_balance=0
         )
 
         # Note: In phase 2 registry indices that have been withdrawn for a long time will be recycled.

specs/simple-serialize.md

@@ -9,6 +9,7 @@ This is a **work in progress** describing typing, serialization and Merkleizatio
     - [Basic types](#basic-types)
     - [Composite types](#composite-types)
     - [Aliases](#aliases)
+    - [Default values](#default-values)
 - [Serialization](#serialization)
     - [`"uintN"`](#uintn)
     - [`"bool"`](#bool)
@@ -50,6 +51,10 @@ For convenience we alias:
 * `"bytes"` to `["byte"]` (this is *not* a basic type)
 * `"bytesN"` to `["byte", N]` (this is *not* a basic type)
 
+### Default values
+
+The default value of a type upon initialization is recursively defined using `0` for `"uintN"`, `False` for `"bool"`, and `[]` for lists.
+
 ## Serialization
 
 We recursively define the `serialize` function which consumes an object `value` (of the type specified) and returns a bytestring of type `"bytes"`.

test_generators/operations/deposits.py

@@ -24,7 +24,6 @@ def build_deposit_data(state,
         pubkey=pubkey,
         withdrawal_credentials=spec.BLS_WITHDRAWAL_PREFIX_BYTE + withdrawal_cred[1:],
         amount=amount,
-        proof_of_possession=spec.EMPTY_SIGNATURE,
     )
     deposit_data.proof_of_possession = bls.sign(
         message_hash=signing_root(deposit_data),

test_libs/pyspec/tests/helpers.py

@@ -9,13 +9,13 @@ import eth2spec.phase0.spec as spec
 from eth2spec.utils.minimal_ssz import signing_root
 from eth2spec.phase0.spec import (
     # constants
-    EMPTY_SIGNATURE,
     ZERO_HASH,
     # SSZ
     Attestation,
     AttestationData,
     AttestationDataAndCustodyBit,
     AttesterSlashing,
+    BeaconBlock,
     BeaconBlockHeader,
     Deposit,
     DepositData,
@@ -30,7 +30,6 @@ from eth2spec.phase0.spec import (
     get_crosslink_committees_at_slot,
     get_current_epoch,
     get_domain,
-    get_empty_block,
     get_epoch_start_slot,
     get_genesis_beacon_state,
     get_previous_epoch,
@@ -115,7 +114,7 @@ def create_genesis_state(num_validators, deposit_data_leaves=None):
 
 
 def build_empty_block_for_next_slot(state):
-    empty_block = get_empty_block()
+    empty_block = BeaconBlock()
     empty_block.slot = state.slot + 1
     previous_block_header = deepcopy(state.latest_block_header)
     if previous_block_header.state_root == spec.ZERO_HASH:
@@ -130,7 +129,6 @@ def build_deposit_data(state, pubkey, privkey, amount):
         # insecurely use pubkey as withdrawal key as well
         withdrawal_credentials=spec.BLS_WITHDRAWAL_PREFIX_BYTE + hash(pubkey)[1:],
         amount=amount,
-        signature=EMPTY_SIGNATURE,
     )
     signature = bls.sign(
         message_hash=signing_root(deposit_data),
@@ -185,7 +183,6 @@ def build_voluntary_exit(state, epoch, validator_index, privkey):
     voluntary_exit = VoluntaryExit(
         epoch=epoch,
         validator_index=validator_index,
-        signature=EMPTY_SIGNATURE,
     )
     voluntary_exit.signature = bls.sign(
         message_hash=signing_root(voluntary_exit),
@@ -235,7 +232,6 @@ def get_valid_proposer_slashing(state):
         previous_block_root=ZERO_HASH,
         state_root=ZERO_HASH,
         block_body_root=ZERO_HASH,
-        signature=EMPTY_SIGNATURE,
     )
     header_2 = deepcopy(header_1)
     header_2.previous_block_root = b'\x02' * 32
@@ -304,7 +300,6 @@ def get_valid_attestation(state, slot=None):
         aggregation_bitfield=aggregation_bitfield,
         data=attestation_data,
         custody_bitfield=custody_bitfield,
-        aggregate_signature=EMPTY_SIGNATURE,
     )
     participants = get_attesting_indices(
         state,

test_libs/pyspec/tests/test_sanity.py

@@ -8,7 +8,6 @@ import eth2spec.phase0.spec as spec
 from eth2spec.utils.minimal_ssz import signing_root
 from eth2spec.phase0.spec import (
     # constants
-    EMPTY_SIGNATURE,
     ZERO_HASH,
     # SSZ
     Deposit,
@@ -350,7 +349,6 @@ def test_voluntary_exit(state):
     voluntary_exit = VoluntaryExit(
         epoch=get_current_epoch(pre_state),
         validator_index=validator_index,
-        signature=EMPTY_SIGNATURE,
     )
     voluntary_exit.signature = bls.sign(
         message_hash=signing_root(voluntary_exit),
@@ -398,7 +396,6 @@ def test_transfer(state):
         fee=0,
         slot=pre_state.slot + 1,
         pubkey=transfer_pubkey,
-        signature=EMPTY_SIGNATURE,
     )
     transfer.signature = bls.sign(
         message_hash=signing_root(transfer),