Fix encoding of array in signTypedData_v4

Currently the behavior of signTypedData_v4 is not according to
https://eips.ethereum.org/EIPS/eip-712 when it comes to encoding arrays.

The eip states: "The array values are encoded as the keccak256 hash of the
concatenated encodeData of their contents".

The behavior instead was to encode array values as the keccak256 of the
concatenated keccak256 of the values.

This worked well for primary types, but not for struct, as encodeData
per spec is: "The encoding of a struct instance is
enc(value₁) ‖ enc(value₂) ‖ … ‖ enc(valueₙ) , i.e. the concatenation of the
encoded member values in the order that they appear in the type.
Each encoded member value is exactly 32-byte long.".

Instead, we were using basically `hashStruct` instead of `encodeData`

src/__snapshots__/sign-typed-data.test.ts.snap

@@ -320,7 +320,7 @@ exports[`TypedDataUtils.encodeData V4 should encode data when called unbound 1`]
 
 exports[`TypedDataUtils.encodeData V4 should encode data when given extraneous types 1`] = `"cddf41b07426e1a761f3da57e35474ae3deaa5b596306531f651c6dc1321e4fd6cdba77591a790691c694fa0be937f835b8a589095e427022aa1035e579ee596"`;
 
-exports[`TypedDataUtils.encodeData V4 should encode data with a custom data type array 1`] = `"077b2e5169bfc57ed1b6acf858d27ae9b8311db1ccf71df99dfcf9efe8eec43856cacfdc07c6f697bc1bc978cf38559d5c729ed1cd1177e047df929e19dc2a2e8548546251a0cc6d0005e1a792e00f85feed5056e580102ed1afa615f87bb130b5aadf3154a261abdd9086fc627b61efca26ae5702701d05cd2305f7c52a2fc8"`;
+exports[`TypedDataUtils.encodeData V4 should encode data with a custom data type array 1`] = `"077b2e5169bfc57ed1b6acf858d27ae9b8311db1ccf71df99dfcf9efe8eec43856cacfdc07c6f697bc1bc978cf38559d5c729ed1cd1177e047df929e19dc2a2ebfe1302b079804af4cd9e10539928375539a1724a1cf42d42b2918298c371eafb5aadf3154a261abdd9086fc627b61efca26ae5702701d05cd2305f7c52a2fc8"`;
 
 exports[`TypedDataUtils.encodeData V4 should encode data with a custom type property set to null 1`] = `"a0cedeb2dc280ba39b857546d74f5549c3a1d7bdc2dd96bf881f76108e23dac2fc71e5fa27ff56c350aa531bc129ebdf613b772b6604664f5d8dbe21b85eb0c80000000000000000000000000000000000000000000000000000000000000000b5aadf3154a261abdd9086fc627b61efca26ae5702701d05cd2305f7c52a2fc8"`;
 
@@ -628,7 +628,7 @@ exports[`TypedDataUtils.hashStruct V4 should hash data when called unbound 1`] =
 
 exports[`TypedDataUtils.hashStruct V4 should hash data when given extraneous types 1`] = `"15d2c54cdaa22a6a3a8dbd89086b2ffcf0853857db9bcf1541765a8f769a63ba"`;
 
-exports[`TypedDataUtils.hashStruct V4 should hash data with a custom data type array 1`] = `"ac26cc7aa2cb9a8a445fae4e48b33f978b558da9b16e26381c53814d3317f541"`;
+exports[`TypedDataUtils.hashStruct V4 should hash data with a custom data type array 1`] = `"e4ef223c74f2085fbac1f734aa89e00985dc1dfa72419eedc9e33b52a6d15a2b"`;
 
 exports[`TypedDataUtils.hashStruct V4 should hash data with a custom type property set to null 1`] = `"fdecfae63c304f6fc7795188607e3838f5bf6798e47f147efdb2c71fcec1335e"`;
 
@@ -1108,7 +1108,7 @@ exports[`signTypedData V4 should sign a typed message with only custom domain se
 
 exports[`signTypedData V4 should sign data when given extraneous types 1`] = `"0x9809571f17ee150687932fb7b993f4437b05caf9c8e64818ab4356b33992f3796636c18e88ba9c6dc140f39f95d8ae5770ad2f17070af208690c82d33f3bc8701c"`;
 
-exports[`signTypedData V4 should sign data with a custom data type array 1`] = `"0x17c484deba479e3e9f821a6d5defc0179ddf52195c0cd75895c936b3ab4d217c6ba7f1f164a3ac9701e1694a04a13f421fb67ec44cd316846326a98b0d5838a01c"`;
+exports[`signTypedData V4 should sign data with a custom data type array 1`] = `"0x96cf12332272746492a9b9a56ff928e6ad2538d4d3faaaaeb7a691720c94e68e5e14d56fa847deff4e8ccbe11e0aa72066f1330cb22045199c33ce67a9cef5cf1c"`;
 
 exports[`signTypedData V4 should sign data with a custom type property set to null 1`] = `"0xc24daccba3391e6f6c3c07c8d62b8c83f7bb4e370613cb2d9ece63a4897d2d044e77e613091a496d8f337854c09ee139e4bca87839d3562ba16a850daa60185a1c"`;
 

src/sign-typed-data.ts

@@ -173,6 +173,7 @@ function encodeField(
   version: SignTypedDataVersion.V3 | SignTypedDataVersion.V4,
 ): [type: string, value: any] {
   validateVersion(version, [SignTypedDataVersion.V3, SignTypedDataVersion.V4]);
+  console.log('ENCODING', types, name, type, value);
 
   if (types[type] !== undefined) {
     return [
@@ -206,6 +207,18 @@ function encodeField(
       );
     }
     const parsedType = type.slice(0, type.lastIndexOf('['));
+
+    // If it's a struct, we concatenate their encodedData and then take the keccak256
+    // as per "The array values are encoded as the keccak256 hash of the concatenated encodeData of their contents"
+    if (types[parsedType] !== undefined) {
+      const typeValuePairs = value.map((item) =>
+        encodeData(parsedType, item, types, version),
+      );
+      console.log(typeValuePairs);
+      return ['bytes32', keccak(Buffer.concat(typeValuePairs))];
+    }
+
+    // Otherwise we use encodeField as it's not a struct
     const typeValuePairs = value.map((item) =>
       encodeField(types, name, parsedType, item, version),
     );