test_bal_nested_delegatecall_storage_writes_net_zero()

Documentation for tests/amsterdam/eip7928_block_level_access_lists/test_block_access_lists.py::test_bal_nested_delegatecall_storage_writes_net_zero@2119b382.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip7928_block_level_access_lists/test_block_access_lists.py::test_bal_nested_delegatecall_storage_writes_net_zero --fork Amsterdam

Test BAL correctly handles nested DELEGATECALL frames where intermediate frames write different values but the deepest frame reverts to original.

Each nesting level writes a different intermediate value, and the deepest frame writes back the original value, resulting in net-zero change.

Example for depth=2 (intermediate_values=[2, 3]): - Pre-state: slot 0 = 1 - Root frame writes: slot 0 = 2 - Child frame writes: slot 0 = 3 - Grandchild frame writes: slot 0 = 1 (back to original) - Expected: No storage_changes (net-zero overall)

Source code in tests/amsterdam/eip7928_block_level_access_lists/test_block_access_lists.py

@pytest.mark.parametrize(
    "intermediate_values",
    [
        pytest.param([2], id="depth_1"),
        pytest.param([2, 3], id="depth_2"),
        pytest.param([2, 3, 4], id="depth_3"),
    ],
)
@pytest.mark.eels_base_coverage
def test_bal_nested_delegatecall_storage_writes_net_zero(
    pre: Alloc,
    blockchain_test: BlockchainTestFiller,
    intermediate_values: list,
) -> None:
    """
    Test BAL correctly handles nested DELEGATECALL frames where intermediate
    frames write different values but the deepest frame reverts to original.

    Each nesting level writes a different intermediate value, and the deepest
    frame writes back the original value, resulting in net-zero change.

    Example for depth=2 (intermediate_values=[2, 3]):
    - Pre-state: slot 0 = 1
    - Root frame writes: slot 0 = 2
    - Child frame writes: slot 0 = 3
    - Grandchild frame writes: slot 0 = 1 (back to original)
    - Expected: No storage_changes (net-zero overall)
    """
    alice = pre.fund_eoa()
    starting_value = 1

    # deepest contract writes back to starting_value
    deepest_code = Op.SSTORE(0, starting_value) + Op.STOP
    next_contract = pre.deploy_contract(code=deepest_code)
    delegate_contracts = [next_contract]

    # Build intermediate contracts (in reverse order) that write then
    # DELEGATECALL. Skip the first value since that's for the root contract
    for value in reversed(intermediate_values[1:]):
        code = (
            Op.SSTORE(0, value)
            + Op.DELEGATECALL(100_000, next_contract, 0, 0, 0, 0)
            + Op.STOP
        )
        next_contract = pre.deploy_contract(code=code)
        delegate_contracts.append(next_contract)

    # root_contract writes first intermediate value, then DELEGATECALLs
    root_contract = pre.deploy_contract(
        code=(
            Op.SSTORE(0, intermediate_values[0])
            + Op.DELEGATECALL(100_000, next_contract, 0, 0, 0, 0)
            + Op.STOP
        ),
        storage={0: starting_value},
    )

    tx = Transaction(
        sender=alice,
        to=root_contract,
        gas_limit=500_000,
    )

    account_expectations = {
        alice: BalAccountExpectation(
            nonce_changes=[BalNonceChange(block_access_index=1, post_nonce=1)],
        ),
        root_contract: BalAccountExpectation(
            storage_reads=[0],
            storage_changes=[],  # validate no changes
        ),
    }
    # All delegate contracts accessed but no changes
    for contract in delegate_contracts:
        account_expectations[contract] = BalAccountExpectation.empty()

    blockchain_test(
        pre=pre,
        blocks=[
            Block(
                txs=[tx],
                expected_block_access_list=BlockAccessListExpectation(
                    account_expectations=account_expectations
                ),
            )
        ],
        post={
            alice: Account(nonce=1),
            root_contract: Account(storage={0: starting_value}),
        },
    )

Parametrized Test Cases

This test generates 3 parametrized test cases across 1 fork.