feat(order_utils.py): sign_hash() (#1254)

Also moved is_valid_signature() into main package module, for
simplicity.

Also consolidated a handul of in-line pylint disable directives into the
.pylintrc config file.

14 files changed, 286 insertions, 110 deletions

diff --git a/python-packages/order_utils/.pylintrc b/python-packages/order_utils/.pylintrc
new file mode 100644
index 000000000..937bc6313
--- /dev/null
+++ b/python-packages/order_utils/.pylintrc
@@ -0,0 +1,3 @@
+[MESSAGES CONTROL]
+disable=C0330,line-too-long,fixme,too-few-public-methods,too-many-ancestors
+# C0330 is "bad hanging indent". we use indents per `black`.
diff --git a/python-packages/order_utils/setup.py b/python-packages/order_utils/setup.py
index 7f1da2f34..5a8db2b64 100755
--- a/python-packages/order_utils/setup.py
+++ b/python-packages/order_utils/setup.py
@@ -24,7 +24,6 @@ class TestCommandExtension(TestCommand):
         exit(pytest.main())
 
 
-# pylint: disable=too-many-ancestors
 class LintCommand(distutils.command.build_py.build_py):
     """Custom setuptools command class for running linters."""
 
@@ -90,7 +89,6 @@ class CleanCommandExtension(clean):
         rmtree("src/0x_order_utils.egg-info", ignore_errors=True)
 
 
-# pylint: disable=too-many-ancestors
 class TestPublishCommand(distutils.command.build_py.build_py):
     """Custom command to publish to test.pypi.org."""
 
@@ -108,7 +106,6 @@ class TestPublishCommand(distutils.command.build_py.build_py):
         )
 
 
-# pylint: disable=too-many-ancestors
 class PublishCommand(distutils.command.build_py.build_py):
     """Custom command to publish to pypi.org."""
 
@@ -119,7 +116,6 @@ class PublishCommand(distutils.command.build_py.build_py):
         subprocess.check_call("twine upload dist/*".split())  # nosec
 
 
-# pylint: disable=too-many-ancestors
 class GanacheCommand(distutils.command.build_py.build_py):
     """Custom command to publish to pypi.org."""
 
diff --git a/python-packages/order_utils/src/index.rst b/python-packages/order_utils/src/index.rst
index b99addabd..4d27a4b17 100644
--- a/python-packages/order_utils/src/index.rst
+++ b/python-packages/order_utils/src/index.rst
@@ -7,6 +7,11 @@ Python zero_ex.order_utils
    :maxdepth: 2
    :caption: Contents:
 
+.. autoclass:: zero_ex.order_utils.Order
+   :members:
+
+See source for class properties.  Sphinx does not easily generate class property docs; pull requests welcome.
+
 .. automodule:: zero_ex.order_utils
    :members:
 
@@ -17,11 +22,6 @@ Python zero_ex.order_utils
 
 .. autoclass:: zero_ex.order_utils.asset_data_utils.ERC721AssetData
 
-See source for class properties.  Sphinx does not easily generate class property docs; pull requests welcome.
-
-.. automodule:: zero_ex.order_utils.signature_utils
-   :members:
-
 Indices and tables
 ==================
 
diff --git a/python-packages/order_utils/src/zero_ex/dev_utils/abi_utils.py b/python-packages/order_utils/src/zero_ex/dev_utils/abi_utils.py
index 9afeacfdf..3fec775b0 100644
--- a/python-packages/order_utils/src/zero_ex/dev_utils/abi_utils.py
+++ b/python-packages/order_utils/src/zero_ex/dev_utils/abi_utils.py
@@ -84,7 +84,6 @@ def method_id(name: str, types: List[str]) -> str:
 
 
 def simple_encode(method: str, *args: Any) -> bytes:
-    # docstring considered all one line by pylint: disable=line-too-long
     r"""Encode a method ABI.
 
     >>> simple_encode("ERC20Token(address)", "0x1dc4c1cefef38a777b15aa20260a54e584b16c48")
diff --git a/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py b/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py
index 08c1b0ea5..1dcfb39a9 100644
--- a/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py
+++ b/python-packages/order_utils/src/zero_ex/dev_utils/type_assertions.py
@@ -2,6 +2,9 @@
 
 from typing import Any
 
+from eth_utils import is_address
+from web3.providers.base import BaseProvider
+
 
 def assert_is_string(value: Any, name: str) -> None:
     """If :param value: isn't of type str, raise a TypeError.
@@ -56,3 +59,31 @@ def assert_is_hex_string(value: Any, name: str) -> None:
     """
     assert_is_string(value, name)
     int(value, 16)  # raises a ValueError if value isn't a base-16 str
+
+
+def assert_is_address(value: Any, name: str) -> None:
+    """Assert that `value` is a valid Ethereum address.
+
+    If `value` isn't a hex string, raise a TypeError.  If it isn't a valid
+    Ethereum address, raise a ValueError.
+    """
+    assert_is_hex_string(value, name)
+    if not is_address(value):
+        raise ValueError(
+            f"Expected variable '{name}' to be a valid Ethereum"
+            + " address, but it's not."
+        )
+
+
+def assert_is_provider(value: Any, name: str) -> None:
+    """Assert that `value` is a Web3 provider.
+
+    If `value` isn't a Web3 provider, raise a TypeError.
+    """
+    # TODO: make this provider check more flexible.
+    # https://app.asana.com/0/684263176955174/901300863045491/f
+    if not isinstance(value, BaseProvider):
+        raise TypeError(
+            f"Expected variable '{name}' to be an instance of a Web3 provider,"
+            + " but it's not."
+        )
diff --git a/python-packages/order_utils/src/zero_ex/order_utils/__init__.py b/python-packages/order_utils/src/zero_ex/order_utils/__init__.py
index fb5bc2f5d..c736d3567 100644
--- a/python-packages/order_utils/src/zero_ex/order_utils/__init__.py
+++ b/python-packages/order_utils/src/zero_ex/order_utils/__init__.py
@@ -10,19 +10,27 @@ just this purpose.  To start it: ``docker run -d -p 8545:8545 0xorg/ganache-cli
 fence smart topic"``.
 """
 
+from enum import auto, Enum
 import json
-from typing import Dict
+from typing import Dict, Tuple
 from pkg_resources import resource_string
 
 from mypy_extensions import TypedDict
 
-from eth_utils import is_address, keccak, to_checksum_address, to_bytes
+from eth_utils import keccak, to_bytes, to_checksum_address
 from web3 import Web3
-from web3.utils import datatypes
 import web3.exceptions
+from web3.providers.base import BaseProvider
+from web3.utils import datatypes
 
+from zero_ex.dev_utils.type_assertions import (
+    assert_is_address,
+    assert_is_hex_string,
+    assert_is_provider,
+)
 
-class Constants:  # pylint: disable=too-few-public-methods
+
+class _Constants:
     """Static data used by order utilities."""
 
     contract_name_to_abi = {
@@ -71,6 +79,18 @@ class Constants:  # pylint: disable=too-few-public-methods
         + b")"
     )
 
+    class SignatureType(Enum):
+        """Enumeration of known signature types."""
+
+        ILLEGAL = 0
+        INVALID = auto()
+        EIP712 = auto()
+        ETH_SIGN = auto()
+        WALLET = auto()
+        VALIDATOR = auto()
+        PRE_SIGNED = auto()
+        N_SIGNATURE_TYPES = auto()
+
 
 class Order(TypedDict):  # pylint: disable=too-many-instance-attributes
     """Object representation of a 0x order."""
@@ -90,14 +110,18 @@ class Order(TypedDict):  # pylint: disable=too-many-instance-attributes
 
 
 def make_empty_order() -> Order:
-    """Construct an empty order."""
+    """Construct an empty order.
+
+    Initializes all strings to "0x0000000000000000000000000000000000000000"
+    and all numbers to 0.
+    """
     return {
-        "maker_address": Constants.null_address,
-        "taker_address": Constants.null_address,
-        "sender_address": Constants.null_address,
-        "fee_recipient_address": Constants.null_address,
-        "maker_asset_data": Constants.null_address,
-        "taker_asset_data": Constants.null_address,
+        "maker_address": _Constants.null_address,
+        "taker_address": _Constants.null_address,
+        "sender_address": _Constants.null_address,
+        "fee_recipient_address": _Constants.null_address,
+        "maker_asset_data": _Constants.null_address,
+        "taker_asset_data": _Constants.null_address,
         "salt": 0,
         "maker_fee": 0,
         "taker_fee": 0,
@@ -108,9 +132,13 @@ def make_empty_order() -> Order:
 
 
 def generate_order_hash_hex(order: Order, exchange_address: str) -> str:
-    # docstring considered all one line by pylint: disable=line-too-long
     """Calculate the hash of the given order as a hexadecimal string.
 
+    :param order: The order to be hashed.  Must conform to `the 0x order JSON schema <https://github.com/0xProject/0x-monorepo/blob/development/packages/json-schemas/schemas/order_schema.json>`_.
+    :param exchange_address: The address to which the 0x Exchange smart
+        contract has been deployed.
+    :rtype: A string, of ASCII hex digits, representing the order hash.
+
     >>> generate_order_hash_hex(
     ...     {
     ...         'maker_address': "0x0000000000000000000000000000000000000000",
@@ -138,12 +166,12 @@ def generate_order_hash_hex(order: Order, exchange_address: str) -> str:
         return i.to_bytes(32, byteorder="big")
 
     eip712_domain_struct_hash = keccak(
-        Constants.eip712_domain_struct_header
+        _Constants.eip712_domain_struct_header
         + pad_20_bytes_to_32(to_bytes(hexstr=exchange_address))
     )
 
     eip712_order_struct_hash = keccak(
-        Constants.eip712_order_schema_hash
+        _Constants.eip712_order_schema_hash
         + pad_20_bytes_to_32(to_bytes(hexstr=order["maker_address"]))
         + pad_20_bytes_to_32(to_bytes(hexstr=order["taker_address"]))
         + pad_20_bytes_to_32(to_bytes(hexstr=order["fee_recipient_address"]))
@@ -159,7 +187,202 @@ def generate_order_hash_hex(order: Order, exchange_address: str) -> str:
     )
 
     return keccak(
-        Constants.eip191_header
+        _Constants.eip191_header
         + eip712_domain_struct_hash
         + eip712_order_struct_hash
     ).hex()
+
+
+def is_valid_signature(
+    provider: BaseProvider, data: str, signature: str, signer_address: str
+) -> Tuple[bool, str]:
+    """Check the validity of the supplied signature.
+
+    Check if the supplied ``signature`` corresponds to signing ``data`` with
+    the private key corresponding to ``signer_address``.
+
+    :param provider: A Web3 provider able to access the 0x Exchange contract.
+    :param data: The hex encoded data signed by the supplied signature.
+    :param signature: The hex encoded signature.
+    :param signer_address: The hex encoded address that signed the data to
+        produce the supplied signature.
+    :rtype: Tuple consisting of a boolean and a string.  Boolean is true if
+        valid, false otherwise.  If false, the string describes the reason.
+
+    >>> is_valid_signature(
+    ...     Web3.HTTPProvider("http://127.0.0.1:8545"),
+    ...     '0x6927e990021d23b1eb7b8789f6a6feaf98fe104bb0cf8259421b79f9a34222b0',
+    ...     '0x1B61a3ed31b43c8780e905a260a35faefcc527be7516aa11c0256729b5b351bc3340349190569279751135161d22529dc25add4f6069af05be04cacbda2ace225403',
+    ...     '0x5409ed021d9299bf6814279a6a1411a7e866a631',
+    ... )
+    (True, '')
+    """  # noqa: E501 (line too long)
+    assert_is_provider(provider, "provider")
+    assert_is_hex_string(data, "data")
+    assert_is_hex_string(signature, "signature")
+    assert_is_address(signer_address, "signer_address")
+
+    web3_instance = Web3(provider)
+    # false positive from pylint: disable=no-member
+    network_id = web3_instance.net.version
+    contract_address = _Constants.network_to_exchange_addr[network_id]
+    # false positive from pylint: disable=no-member
+    contract: datatypes.Contract = web3_instance.eth.contract(
+        address=to_checksum_address(contract_address),
+        abi=_Constants.contract_name_to_abi["Exchange"],
+    )
+    try:
+        return (
+            contract.call().isValidSignature(
+                data, to_checksum_address(signer_address), signature
+            ),
+            "",
+        )
+    except web3.exceptions.BadFunctionCallOutput as exception:
+        known_revert_reasons = [
+            "LENGTH_GREATER_THAN_0_REQUIRED",
+            "SIGNATURE_ILLEGAL",
+            "SIGNATURE_UNSUPPORTED",
+            "LENGTH_0_REQUIRED",
+            "LENGTH_65_REQUIRED",
+        ]
+        for known_revert_reason in known_revert_reasons:
+            if known_revert_reason in str(exception):
+                return (False, known_revert_reason)
+        return (False, f"Unknown: {exception}")
+
+
+class ECSignature(TypedDict):
+    """Object representation of an elliptic curve signature's parameters."""
+
+    v: int
+    r: str
+    s: str
+
+
+def _parse_signature_hex_as_vrs(signature_hex: str) -> ECSignature:
+    """Parse signature hex as a concatentation of EC parameters ordered V, R, S.
+
+    >>> _parse_signature_hex_as_vrs('0x1b117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d872871137feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b03')
+    {'v': 27, 'r': '117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d87287113', 's': '7feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b'}
+    """  # noqa: E501 (line too long)
+    signature: ECSignature = {
+        "v": int(signature_hex[2:4], 16),
+        "r": signature_hex[4:68],
+        "s": signature_hex[68:132],
+    }
+    if signature["v"] == 0 or signature["v"] == 1:
+        signature["v"] = signature["v"] + 27
+    return signature
+
+
+def _parse_signature_hex_as_rsv(signature_hex: str) -> ECSignature:
+    """Parse signature hex as a concatentation of EC parameters ordered R, S, V.
+
+    >>> _parse_signature_hex_as_rsv('0x117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d872871137feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b00')
+    {'r': '117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d87287113', 's': '7feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b', 'v': 27}
+    """  # noqa: E501 (line too long)
+    signature: ECSignature = {
+        "r": signature_hex[2:66],
+        "s": signature_hex[66:130],
+        "v": int(signature_hex[130:132], 16),
+    }
+    if signature["v"] == 0 or signature["v"] == 1:
+        signature["v"] = signature["v"] + 27
+    return signature
+
+
+def _convert_ec_signature_to_vrs_hex(signature: ECSignature) -> str:
+    """Convert elliptic curve signature object to hex hash string.
+
+    >>> _convert_ec_signature_to_vrs_hex(
+    ...     {
+    ...         'r': '117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d87287113',
+    ...         's': '7feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b',
+    ...         'v': 27
+    ...     }
+    ... )
+    '0x1b117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d872871137feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b'
+    """  # noqa: E501 (line too long)
+    return (
+        "0x"
+        + signature["v"].to_bytes(1, byteorder="big").hex()
+        + signature["r"]
+        + signature["s"]
+    )
+
+
+def sign_hash(
+    provider: BaseProvider, signer_address: str, hash_hex: str
+) -> str:
+    """Sign a message with the given hash, and return the signature.
+
+    :param provider: A Web3 provider.
+    :param signer_address: The address of the signing account.
+    :param hash_hex: A hex string representing the hash, like that returned
+        from `generate_order_hash_hex()`.
+    :rtype: A string, of ASCII hex digits, representing the signature.
+
+    >>> provider = Web3.HTTPProvider("http://127.0.0.1:8545")
+    >>> sign_hash(
+    ...     provider,
+    ...     Web3(provider).personal.listAccounts[0],
+    ...     '0x34decbedc118904df65f379a175bb39ca18209d6ce41d5ed549d54e6e0a95004',
+    ... )
+    '0x1b117902c86dfb95fe0d1badd983ee166ad259b27acb220174cbb4460d872871137feabdfe76e05924b484789f79af4ee7fa29ec006cedce1bbf369320d034e10b03'
+    """  # noqa: E501 (line too long)
+    assert_is_provider(provider, "provider")
+    assert_is_address(signer_address, "signer_address")
+    assert_is_hex_string(hash_hex, "hash_hex")
+
+    web3_instance = Web3(provider)
+    # false positive from pylint: disable=no-member
+    signature = web3_instance.eth.sign(  # type: ignore
+        signer_address, hexstr=hash_hex.replace("0x", "")
+    ).hex()
+
+    valid_v_param_values = [27, 28]
+
+    # HACK: There is no consensus on whether the signatureHex string should be
+    # formatted as v + r + s OR r + s + v, and different clients (even
+    # different versions of the same client) return the signature params in
+    # different orders. In order to support all client implementations, we
+    # parse the signature in both ways, and evaluate if either one is a valid
+    # signature.  r + s + v is the most prevalent format from eth_sign, so we
+    # attempt this first.
+
+    ec_signature = _parse_signature_hex_as_rsv(signature)
+    if ec_signature["v"] in valid_v_param_values:
+        signature_as_vrst_hex = (
+            _convert_ec_signature_to_vrs_hex(ec_signature)
+            + _Constants.SignatureType.ETH_SIGN.value.to_bytes(
+                1, byteorder="big"
+            ).hex()
+        )
+
+        (valid, _) = is_valid_signature(
+            provider, hash_hex, signature_as_vrst_hex, signer_address
+        )
+
+        if valid is True:
+            return signature_as_vrst_hex
+
+    ec_signature = _parse_signature_hex_as_vrs(signature)
+    if ec_signature["v"] in valid_v_param_values:
+        signature_as_vrst_hex = (
+            _convert_ec_signature_to_vrs_hex(ec_signature)
+            + _Constants.SignatureType.ETH_SIGN.value.to_bytes(
+                1, byteorder="big"
+            ).hex()
+        )
+        (valid, _) = is_valid_signature(
+            provider, hash_hex, signature_as_vrst_hex, signer_address
+        )
+
+        if valid is True:
+            return signature_as_vrst_hex
+
+    raise RuntimeError(
+        "Signature returned from web3 provider is in an unknown format."
+        + " Attempted to parse as RSV and as VRS."
+    )
diff --git a/python-packages/order_utils/src/zero_ex/order_utils/asset_data_utils.py b/python-packages/order_utils/src/zero_ex/order_utils/asset_data_utils.py
index e6f9a07c1..fab7479d2 100644
--- a/python-packages/order_utils/src/zero_ex/order_utils/asset_data_utils.py
+++ b/python-packages/order_utils/src/zero_ex/order_utils/asset_data_utils.py
@@ -47,7 +47,6 @@ def encode_erc20_asset_data(token_address: str) -> str:
 
 
 def decode_erc20_asset_data(asset_data: str) -> ERC20AssetData:
-    # docstring considered all one line by pylint: disable=line-too-long
     """Decode an ERC20 asset data hex string.
 
     :param asset_data: String produced by prior call to encode_erc20_asset_data()
@@ -82,7 +81,6 @@ def decode_erc20_asset_data(asset_data: str) -> ERC20AssetData:
 
 
 def encode_erc721_asset_data(token_address: str, token_id: int) -> str:
-    # docstring considered all one line by pylint: disable=line-too-long
     """Encode an ERC721 asset data hex string.
 
     :param token_address: the ERC721 token's contract address.
@@ -105,7 +103,6 @@ def encode_erc721_asset_data(token_address: str, token_id: int) -> str:
 
 
 def decode_erc721_asset_data(asset_data: str) -> ERC721AssetData:
-    # docstring considered all one line by pylint: disable=line-too-long
     """Decode an ERC721 asset data hex string.
 
     >>> decode_erc721_asset_data('0x025717920000000000000000000000001dc4c1cefef38a777b15aa20260a54e584b16c480000000000000000000000000000000000000000000000000000000000000001')
@@ -121,7 +118,6 @@ def decode_erc721_asset_data(asset_data: str) -> ERC721AssetData:
         )
 
     asset_proxy_id: str = asset_data[0:SELECTOR_LENGTH]
-    # prefer `black` formatting.  pylint: disable=C0330
     if asset_proxy_id != abi_utils.method_id(
         "ERC721Token", ["address", "uint256"]
     ):
diff --git a/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py b/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py
deleted file mode 100644
index 2e75be6d5..000000000
--- a/python-packages/order_utils/src/zero_ex/order_utils/signature_utils.py
+++ /dev/null
@@ -1,75 +0,0 @@
-"""Signature utilities."""
-
-from typing import Tuple
-
-from eth_utils import is_address, to_checksum_address
-from web3 import Web3
-import web3.exceptions
-from web3.utils import datatypes
-
-from zero_ex.order_utils import Constants
-from zero_ex.dev_utils.type_assertions import assert_is_hex_string
-
-
-# prefer `black` formatting. pylint: disable=C0330
-def is_valid_signature(
-    provider: Web3.HTTPProvider, data: str, signature: str, signer_address: str
-) -> Tuple[bool, str]:
-    # docstring considered all one line by pylint: disable=line-too-long
-    """Check the validity of the supplied signature.
-
-    Check if the supplied ``signature`` corresponds to signing ``data`` with
-    the private key corresponding to ``signer_address``.
-
-    :param provider: A Web3 provider able to access the 0x Exchange contract.
-    :param data: The hex encoded data signed by the supplied signature.
-    :param signature: The hex encoded signature.
-    :param signer_address: The hex encoded address that signed the data to
-        produce the supplied signature.
-    :rtype: Boolean indicating whether the given signature is valid.
-
-    >>> is_valid_signature(
-    ...     Web3.HTTPProvider("http://127.0.0.1:8545"),
-    ...     '0x6927e990021d23b1eb7b8789f6a6feaf98fe104bb0cf8259421b79f9a34222b0',
-    ...     '0x1B61a3ed31b43c8780e905a260a35faefcc527be7516aa11c0256729b5b351bc3340349190569279751135161d22529dc25add4f6069af05be04cacbda2ace225403',
-    ...     '0x5409ed021d9299bf6814279a6a1411a7e866a631',
-    ... )
-    (True, '')
-    """  # noqa: E501 (line too long)
-    # TODO: make this provider check more flexible. pylint: disable=fixme
-    # https://app.asana.com/0/684263176955174/901300863045491/f
-    if not isinstance(provider, Web3.HTTPProvider):
-        raise TypeError("provider is not a Web3.HTTPProvider")
-    assert_is_hex_string(data, "data")
-    assert_is_hex_string(signature, "signature")
-    assert_is_hex_string(signer_address, "signer_address")
-    if not is_address(signer_address):
-        raise ValueError("signer_address is not a valid address")
-
-    web3_instance = Web3(provider)
-    # false positive from pylint: disable=no-member
-    network_id = web3_instance.net.version
-    contract_address = Constants.network_to_exchange_addr[network_id]
-    # false positive from pylint: disable=no-member
-    contract: datatypes.Contract = web3_instance.eth.contract(
-        address=to_checksum_address(contract_address),
-        abi=Constants.contract_name_to_abi["Exchange"],
-    )
-    try:
-        return (
-            contract.call().isValidSignature(
-                data, to_checksum_address(signer_address), signature
-            ),
-            "",
-        )
-    except web3.exceptions.BadFunctionCallOutput as exception:
-        known_revert_reasons = [
-            "LENGTH_GREATER_THAN_0_REQUIRED",
-            "SIGNATURE_UNSUPPORTED",
-            "LENGTH_0_REQUIRED",
-            "LENGTH_65_REQUIRED",
-        ]
-        for known_revert_reason in known_revert_reasons:
-            if known_revert_reason in str(exception):
-                return (False, known_revert_reason)
-        return (False, f"Unknown: {exception}")
diff --git a/python-packages/order_utils/stubs/web3/__init__.pyi b/python-packages/order_utils/stubs/web3/__init__.pyi
index fcecc7434..b2af95475 100644
--- a/python-packages/order_utils/stubs/web3/__init__.pyi
+++ b/python-packages/order_utils/stubs/web3/__init__.pyi
@@ -1,12 +1,14 @@
 from typing import Dict, Optional, Union
 
 from web3.utils import datatypes
+from web3.providers.base import BaseProvider
 
 
 class Web3:
-    class HTTPProvider: ...
+    class HTTPProvider(BaseProvider):
+        ...
 
-    def __init__(self, provider: HTTPProvider) -> None: ...
+    def __init__(self, provider: BaseProvider) -> None: ...
 
     @staticmethod
     def sha3(
diff --git a/python-packages/order_utils/stubs/web3/providers/__init__.pyi b/python-packages/order_utils/stubs/web3/providers/__init__.pyi
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/python-packages/order_utils/stubs/web3/providers/__init__.pyi
diff --git a/python-packages/order_utils/stubs/web3/providers/base.pyi b/python-packages/order_utils/stubs/web3/providers/base.pyi
new file mode 100644
index 000000000..82ca9e3da
--- /dev/null
+++ b/python-packages/order_utils/stubs/web3/providers/base.pyi
@@ -0,0 +1,2 @@
+class BaseProvider:
+    ...
diff --git a/python-packages/order_utils/test/test_doctest.py b/python-packages/order_utils/test/test_doctest.py
index 2b0350ac0..f692b3b6c 100644
--- a/python-packages/order_utils/test/test_doctest.py
+++ b/python-packages/order_utils/test/test_doctest.py
@@ -8,7 +8,6 @@ import zero_ex
 
 def test_all_doctests():
     """Gather zero_ex.* modules and doctest them."""
-    # prefer `black` formatting. pylint: disable=bad-continuation
     for (importer, modname, _) in pkgutil.walk_packages(
         path=zero_ex.__path__, prefix="zero_ex."
     ):
diff --git a/python-packages/order_utils/test/test_generate_order_hash_hex.py b/python-packages/order_utils/test/test_generate_order_hash_hex.py
index e393f38d7..af78d208c 100644
--- a/python-packages/order_utils/test/test_generate_order_hash_hex.py
+++ b/python-packages/order_utils/test/test_generate_order_hash_hex.py
@@ -3,7 +3,7 @@
 from zero_ex.order_utils import (
     generate_order_hash_hex,
     make_empty_order,
-    Constants,
+    _Constants,
 )
 
 
@@ -13,6 +13,6 @@ def test_get_order_hash_hex__empty_order():
         "faa49b35faeb9197e9c3ba7a52075e6dad19739549f153b77dfcf59408a4b422"
     )
     actual_hash_hex = generate_order_hash_hex(
-        make_empty_order(), Constants.null_address
+        make_empty_order(), _Constants.null_address
     )
     assert actual_hash_hex == expected_hash_hex
diff --git a/python-packages/order_utils/test/test_signature_utils.py b/python-packages/order_utils/test/test_signature_utils.py
index b688e03a1..c5acc9d62 100644
--- a/python-packages/order_utils/test/test_signature_utils.py
+++ b/python-packages/order_utils/test/test_signature_utils.py
@@ -3,7 +3,7 @@
 import pytest
 from web3 import Web3
 
-from zero_ex.order_utils.signature_utils import is_valid_signature
+from zero_ex.order_utils import is_valid_signature
 
 
 def test_is_valid_signature__provider_wrong_type():