fixed and linter

src/wallet.test.ts

@@ -478,6 +478,51 @@ describe('wallet', () => {
     });
   });
 
+  it('should not throw if verifyingContract is "cosmos"', async () => {
+    const { engine } = createTestSetup();
+    const getAccounts = async () => testAddresses.slice();
+    const witnessedMsgParams: TypedMessageParams[] = [];
+    const processTypedMessageV3 = async (msgParams: TypedMessageParams) => {
+      witnessedMsgParams.push(msgParams);
+      // Assume testMsgSig is the expected signature result
+      return testMsgSig;
+    };
+
+    engine.push(createWalletMiddleware({ getAccounts, processTypedMessageV3 }));
+
+    const message = {
+      types: {
+        EIP712Domain: [
+          { name: 'name', type: 'string' },
+          { name: 'version', type: 'string' },
+          { name: 'chainId', type: 'uint256' },
+          { name: 'verifyingContract', type: 'address' },
+        ],
+      },
+      primaryType: 'EIP712Domain',
+      message: {},
+      domain: {
+        verifyingContract: 'cosmos',
+      },
+    };
+
+    const stringifiedMessage = JSON.stringify(message);
+
+    const payload = {
+      method: 'eth_signTypedData_v3',
+      params: [testAddresses[0], stringifiedMessage], // Assuming testAddresses[0] is a valid address from your setup
+    };
+
+    const promise = pify(engine.handle).call(engine, payload);
+    const result = await promise;
+    expect(result).toStrictEqual({
+      id: undefined,
+      jsonrpc: undefined,
+      result:
+        '0x68dc980608bceb5f99f691e62c32caccaee05317309015e9454eba1a14c3cd4505d1dd098b8339801239c9bcaac3c4df95569dcf307108b92f68711379be14d81c',
+    });
+  });
+
   describe('signTypedDataV4', () => {
     const getMsgParams = (verifyingContract?: string) => ({
       types: {

src/wallet.ts

@@ -497,10 +497,20 @@ WalletMiddlewareOptions): JsonRpcMiddleware<any, Block> {
  * Validates verifyingContract of typedSignMessage.
  *
  * @param data - The data passed in typedSign request.
+ * This function allows the verifyingContract to be either:
+ * - A valid hex address
+ * - The string "cosmos" (as it is hard-coded in some Cosmos ecosystem's EVM adapters)
+ * - An empty string
  */
 function validateVerifyingContract(data: string) {
   const { domain: { verifyingContract } = {} } = parseTypedMessage(data);
-  if (verifyingContract && !(isValidHexAddress(verifyingContract) || verifyingContract == 'cosmos')) {
+  if (
+    verifyingContract &&
+    !(
+      isValidHexAddress(verifyingContract) ||
+      (verifyingContract as any) === 'cosmos'
+    )
+  ) {
     throw rpcErrors.invalidInput();
   }
 }