♻️ Make EIP712DomainSeparator Module-Friendly (#229)

### 🕓 Changelog

This PR refactors the `EIP712DomainSeparator` contract to make it
module-friendly and ready for the breaking `0.4.0` release.

---------

Signed-off-by: Pascal Marco Caversaccio <pascal.caversaccio@hotmail.ch>

.gas-snapshot

@@ -122,13 +122,13 @@ ECDSATest:testRecoverWithTooShortSignature() (gas: 14545)
 ECDSATest:testRecoverWithValidSignature() (gas: 21604)
 ECDSATest:testRecoverWithWrongMessage() (gas: 21616)
 ECDSATest:testRecoverWithWrongVersion() (gas: 15782)
-EIP712DomainSeparatorTest:testCachedDomainSeparatorV4() (gas: 10440)
-EIP712DomainSeparatorTest:testDomainSeparatorV4() (gas: 11715)
-EIP712DomainSeparatorTest:testEIP712Domain() (gas: 18648)
-EIP712DomainSeparatorTest:testFuzzDomainSeparatorV4(uint8) (runs: 256, μ: 11870, ~: 11890)
-EIP712DomainSeparatorTest:testFuzzEIP712Domain(bytes1,uint8,bytes32,uint256[]) (runs: 256, μ: 22030, ~: 22034)
-EIP712DomainSeparatorTest:testFuzzHashTypedDataV4(address,address,uint256,uint256,uint64) (runs: 256, μ: 10577, ~: 10577)
-EIP712DomainSeparatorTest:testHashTypedDataV4() (gas: 13523)
+EIP712DomainSeparatorTest:testCachedDomainSeparatorV4() (gas: 10476)
+EIP712DomainSeparatorTest:testDomainSeparatorV4() (gas: 11731)
+EIP712DomainSeparatorTest:testEIP712Domain() (gas: 18661)
+EIP712DomainSeparatorTest:testFuzzDomainSeparatorV4(uint8) (runs: 256, μ: 11888, ~: 11906)
+EIP712DomainSeparatorTest:testFuzzEIP712Domain(bytes1,uint8,bytes32,uint256[]) (runs: 256, μ: 22026, ~: 22027)
+EIP712DomainSeparatorTest:testFuzzHashTypedDataV4(address,address,uint256,uint256,uint64) (runs: 256, μ: 10685, ~: 10685)
+EIP712DomainSeparatorTest:testHashTypedDataV4() (gas: 13631)
 ERC1155Invariants:invariantOwner() (runs: 256, calls: 3840, reverts: 3429)
 ERC1155Test:testBalanceOfBatchCase1() (gas: 281522)
 ERC1155Test:testBalanceOfBatchCase2() (gas: 236092)

CHANGELOG.md

@@ -18,6 +18,7 @@
   - [`ECDSA`](https://github.com/pcaversaccio/snekmate/blob/v0.1.0/src/snekmate/utils/ECDSA.vy): Make `ECDSA` module-friendly. ([#227](https://github.com/pcaversaccio/snekmate/pull/227))
   - [`MessageHashUtils`](https://github.com/pcaversaccio/snekmate/blob/v0.1.0/src/snekmate/utils/MessageHashUtils.vy): Move the `ECDSA` message hash methods to a separate `MessageHashUtils` library module. ([#227](https://github.com/pcaversaccio/snekmate/pull/227))
   - [`SignatureChecker`](https://github.com/pcaversaccio/snekmate/blob/v0.1.0/src/snekmate/utils/SignatureChecker.vy): Make `SignatureChecker` module-friendly. ([#228](https://github.com/pcaversaccio/snekmate/pull/228))
+  - [`EIP712DomainSeparator`](https://github.com/pcaversaccio/snekmate/blob/v0.1.0/src/snekmate/utils/EIP712DomainSeparator.vy): Make `EIP712DomainSeparator` module-friendly. ([#229](https://github.com/pcaversaccio/snekmate/pull/229))
 - **Vyper Contract Deployer**
   - [`VyperDeployer`](https://github.com/pcaversaccio/snekmate/blob/v0.1.0/lib/utils/VyperDeployer.sol): Improve error message in the event of a Vyper compilation error. ([#219](https://github.com/pcaversaccio/snekmate/pull/219))
 

README.md

@@ -71,7 +71,8 @@ src
             ├── Create2AddressMock — "Create2Address Module Reference Implementation"
             ├── ECDSAMock — "ECDSA Module Reference Implementation"
             ├── MessageHashUtilsMock — "MessageHashUtils Module Reference Implementation"
-            └── SignatureCheckerMock — "SignatureChecker Module Reference Implementation"
+            ├── SignatureCheckerMock — "SignatureChecker Module Reference Implementation"
+            └── EIP712DomainSeparatorMock — "EIP712DomainSeparator Module Reference Implementation"
 ```
 
 ## 🎛 Installation

src/snekmate/governance/TimelockController.vy

@@ -774,7 +774,7 @@ def _execute(target: address, amount: uint256, payload: Bytes[1_024]):
     success: bool = empty(bool)
     success, return_data = raw_call(target, payload, max_outsize=255, value=amount, revert_on_failure=False)
     if (not(success)):
-        if len(return_data) != empty(uint256):
+        if (len(return_data) != empty(uint256)):
             # Bubble up the revert reason.
             raw_revert(return_data)
         else:

src/snekmate/utils/EIP712DomainSeparator.vy

@@ -21,6 +21,13 @@ import interfaces.IERC5267 as IERC5267
 implements: IERC5267
 
 
+# @dev We import the `MessageHashUtils` module.
+# @notice Please note that the `MessageHashUtils`
+# module is stateless and therefore does not require
+# the `uses` keyword for usage.
+from . import MessageHashUtils as message_hash_utils
+
+
 # @dev The 32-byte type hash for the EIP-712 domain separator.
 _TYPE_HASH: constant(bytes32) = keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)")
 
@@ -81,31 +88,6 @@ def __init__(name_: String[50], version_: String[20]):
     _CACHED_SELF = self
 
 
-@external
-@view
-def domain_separator_v4() -> bytes32:
-    """
-    @dev Returns the domain separator for the current chain.
-    @return bytes32 The 32-byte domain separator.
-    """
-    return self._domain_separator_v4()
-
-
-@external
-@view
-def hash_typed_data_v4(struct_hash: bytes32) -> bytes32:
-    """
-    @dev Returns the hash of the fully encoded EIP-712
-         message for this domain.
-    @notice The definition of the hashed struct can be found here:
-            https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct.
-    @param struct_hash The 32-byte hashed struct.
-    @return bytes32 The 32-byte fully encoded EIP712
-            message hash for this domain.
-    """
-    return self._to_typed_data_hash(self._domain_separator_v4(), struct_hash)
-
-
 @external
 @view
 def eip712Domain() -> (bytes1, String[50], String[20], uint256, address, bytes32, DynArray[uint256, 128]):
@@ -136,14 +118,13 @@ def eip712Domain() -> (bytes1, String[50], String[20], uint256, address, bytes32
 @view
 def _domain_separator_v4() -> bytes32:
     """
-    @dev An `internal` helper function that returns the domain separator
-         for the current chain.
+    @dev Returns the domain separator for the current chain.
     @return bytes32 The 32-byte domain separator.
     """
     if (self == _CACHED_SELF and chain.id == _CACHED_CHAIN_ID):
         return _CACHED_DOMAIN_SEPARATOR
-    else:
-        return self._build_domain_separator()
+
+    return self._build_domain_separator()
 
 
 @internal
@@ -157,11 +138,15 @@ def _build_domain_separator() -> bytes32:
 
 
 @internal
-@pure
-def _to_typed_data_hash(domain_separator: bytes32, struct_hash: bytes32) -> bytes32:
+@view
+def _hash_typed_data_v4(struct_hash: bytes32) -> bytes32:
     """
-    @dev Sourced from {ECDSA-to_typed_data_hash}.
-    @notice See {ECDSA-to_typed_data_hash} for the
-            function docstring.
+    @dev Returns the hash of the fully encoded EIP-712
+         message for this domain.
+    @notice The definition of the hashed struct can be found here:
+            https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct.
+    @param struct_hash The 32-byte hashed struct.
+    @return bytes32 The 32-byte fully encoded EIP712
+            message hash for this domain.
     """
-    return keccak256(concat(b"\x19\x01", domain_separator, struct_hash))
+    return message_hash_utils._to_typed_data_hash(self._domain_separator_v4(), struct_hash)

src/snekmate/utils/mocks/EIP712DomainSeparatorMock.vy

@@ -0,0 +1,76 @@
+# pragma version ~=0.4.0b6
+"""
+@title EIP712DomainSeparator Module Reference Implementation
+@custom:contract-name EIP712DomainSeparatorMock
+@license GNU Affero General Public License v3.0 only
+@author pcaversaccio
+"""
+
+
+# @dev We import and implement the `IERC5267` interface,
+# which is written using standard Vyper syntax.
+from ..interfaces import IERC5267
+implements: IERC5267
+
+
+# @dev We import and initialise the `EIP712DomainSeparator` module.
+from .. import EIP712DomainSeparator as ed
+initializes: ed
+
+
+# @dev We export (i.e. the runtime bytecode exposes these
+# functions externally, allowing them to be called using
+# the ABI encoding specification) the `external` function
+# `eip712Domain` from the `EIP712DomainSeparator` module.
+# @notice Please note that you must always also export (if
+# required by the contract logic) `public` declared `constant`,
+# `immutable`, and state variables, for which Vyper automatically
+# generates an `external` getter function for the variable.
+exports: ed.eip712Domain
+
+
+@deploy
+@payable
+def __init__(name_: String[50], version_: String[20]):
+    """
+    @dev Initialises the domain separator and the parameter caches.
+         To omit the opcodes for checking the `msg.value` in the
+         creation-time EVM bytecode, the constructor is declared as
+         `payable`.
+    @notice The definition of the domain separator can be found here:
+            https://eips.ethereum.org/EIPS/eip-712#definition-of-domainseparator.
+            Since the Vyper design requires strings of fixed size,
+            we arbitrarily set the maximum length for `name` to 50
+            characters and `version` to 20 characters.
+    @param name_ The maximum 50-character user-readable string name
+           of the signing domain, i.e. the name of the dApp or protocol.
+    @param version_ The maximum 20-character current main version of
+           the signing domain. Signatures from different versions are
+           not compatible.
+    """
+    ed.__init__(name_, version_)
+
+
+@external
+@view
+def domain_separator_v4() -> bytes32:
+    """
+    @dev Returns the domain separator for the current chain.
+    @return bytes32 The 32-byte domain separator.
+    """
+    return ed._domain_separator_v4()
+
+
+@external
+@view
+def hash_typed_data_v4(struct_hash: bytes32) -> bytes32:
+    """
+    @dev Returns the hash of the fully encoded EIP-712
+         message for this domain.
+    @notice The definition of the hashed struct can be found here:
+            https://eips.ethereum.org/EIPS/eip-712#definition-of-hashstruct.
+    @param struct_hash The 32-byte hashed struct.
+    @return bytes32 The 32-byte fully encoded EIP712
+            message hash for this domain.
+    """
+    return ed._hash_typed_data_v4(struct_hash)

test/utils/EIP712DomainSeparator.t.sol

@@ -36,8 +36,8 @@ contract EIP712DomainSeparatorTest is Test {
         bytes memory args = abi.encode(_NAME, _VERSION);
         EIP712domainSeparator = IEIP712DomainSeparator(
             vyperDeployer.deployContract(
-                "src/snekmate/utils/",
-                "EIP712DomainSeparator",
+                "src/snekmate/utils/mocks/",
+                "EIP712DomainSeparatorMock",
                 args
             )
         );