Update Interfaces for IValidator and IWallet

contracts/exchange/contracts/examples/Validator.sol

@@ -21,7 +21,7 @@ pragma solidity ^0.5.5;
 import "../src/interfaces/IValidator.sol";
 
 
-contract Validator is 
+contract Validator is
     IValidator
 {
 
@@ -48,9 +48,11 @@ contract Validator is
     )
         external
         view
-        returns (bool isValid)
+        returns (bytes4)
     {
-        return (signerAddress == VALID_SIGNER);
+        require(signerAddress == VALID_SIGNER, "INVALID_SIGNER");
+        bytes4 magic_salt = bytes4(keccak256("isValidValidatorSignature(address,bytes32,address,bytes)"));
+        return magic_salt;
     }
     // solhint-enable no-unused-vars
 }

contracts/exchange/contracts/examples/Wallet.sol

@@ -22,7 +22,7 @@ import "../src/interfaces/IWallet.sol";
 import "@0x/contracts-utils/contracts/src/LibBytes.sol";
 
 
-contract Wallet is 
+contract Wallet is
     IWallet
 {
     using LibBytes for bytes;
@@ -48,7 +48,7 @@ contract Wallet is
     )
         external
         view
-        returns (bool isValid)
+        returns (bytes4)
     {
         require(
             eip712Signature.length == 65,
@@ -59,7 +59,8 @@ contract Wallet is
         bytes32 r = eip712Signature.readBytes32(1);
         bytes32 s = eip712Signature.readBytes32(33);
         address recoveredAddress = ecrecover(hash, v, r, s);
-        isValid = WALLET_OWNER == recoveredAddress;
-        return isValid;
+        require(WALLET_OWNER == recoveredAddress, "INVALID_SIGNATURE");
+        bytes4 magic_salt = bytes4(keccak256("isValidWalletSignature(bytes32,address,bytes)"));
+        return magic_salt;
     }
 }

contracts/exchange/contracts/src/interfaces/IValidator.sol

@@ -25,7 +25,8 @@ contract IValidator {
     /// @param hash Message hash that is signed.
     /// @param signerAddress Address that should have signed the given hash.
     /// @param signature Proof of signing.
-    /// @return Validity of order signature.
+    /// @return Magic bytes4 value if the signature is valid.
+    ///         Magic value is bytes4(keccak256("isValidValidatorSignature(address,bytes32,address,bytes)"))
     function isValidSignature(
         bytes32 hash,
         address signerAddress,
@@ -33,5 +34,5 @@ contract IValidator {
     )
         external
         view
-        returns (bool isValid);
+        returns (bytes4 isValid);
 }

contracts/exchange/contracts/src/interfaces/IWallet.sol

@@ -24,12 +24,13 @@ contract IWallet {
     /// @dev Verifies that a signature is valid.
     /// @param hash Message hash that is signed.
     /// @param signature Proof of signing.
-    /// @return Validity of order signature.
+    /// @return Magic bytes4 value if the signature is valid.
+    ///         Magic value is bytes4(keccak256("isValidWalletSignature(bytes32,address,bytes)"))
     function isValidSignature(
         bytes32 hash,
         bytes calldata signature
     )
         external
         view
-        returns (bool isValid);
+        returns (bytes4 isValid);
 }

packages/contract-artifacts/artifacts/IValidator.json

@@ -6,12 +6,12 @@
             {
                 "constant": true,
                 "inputs": [
-                    { "name": "hash", "type": "bytes32" },
-                    { "name": "signerAddress", "type": "address" },
-                    { "name": "signature", "type": "bytes" }
+                    { "internalType": "bytes32", "name": "hash", "type": "bytes32" },
+                    { "internalType": "address", "name": "signerAddress", "type": "address" },
+                    { "internalType": "bytes", "name": "signature", "type": "bytes" }
                 ],
                 "name": "isValidSignature",
-                "outputs": [{ "name": "isValid", "type": "bool" }],
+                "outputs": [{ "internalType": "bytes4", "name": "isValid", "type": "bytes4" }],
                 "payable": false,
                 "stateMutability": "view",
                 "type": "function"
@@ -26,7 +26,7 @@
                         "signature": "Proof of signing.",
                         "signerAddress": "Address that should have signed the given hash."
                     },
-                    "return": "Validity of order signature."
+                    "return": "Magic bytes4 value if the signature is valid.         Magic value is bytes4(keccak256(\"isValidValidatorSignature(address,bytes32,address,bytes)\"))"
                 }
             }
         },

packages/contract-artifacts/artifacts/IWallet.json

@@ -5,9 +5,12 @@
         "abi": [
             {
                 "constant": true,
-                "inputs": [{ "name": "hash", "type": "bytes32" }, { "name": "signature", "type": "bytes" }],
+                "inputs": [
+                    { "internalType": "bytes32", "name": "hash", "type": "bytes32" },
+                    { "internalType": "bytes", "name": "signature", "type": "bytes" }
+                ],
                 "name": "isValidSignature",
-                "outputs": [{ "name": "isValid", "type": "bool" }],
+                "outputs": [{ "internalType": "bytes4", "name": "isValid", "type": "bytes4" }],
                 "payable": false,
                 "stateMutability": "view",
                 "type": "function"
@@ -18,7 +21,7 @@
                 "isValidSignature(bytes32,bytes)": {
                     "details": "Verifies that a signature is valid.",
                     "params": { "hash": "Message hash that is signed.", "signature": "Proof of signing." },
-                    "return": "Validity of order signature."
+                    "return": "Magic bytes4 value if the signature is valid.         Magic value is bytes4(keccak256(\"isValidWalletSignature(bytes32,address,bytes)\"))"
                 }
             }
         },