Pass methodSig in empty string for fallback pattern

services/construction/contract_call_data.go

@@ -87,16 +87,16 @@ func ConstructContractCallDataGeneric(methodSig string, methodArgs interface{})
 	}
 }
 
-// preprocessArgs converts methodArgs to a string value if methodSig is a 4-byte hex string.
-// In this case, we expect methodArgs containing the pre-compiled ABI data.
+// preprocessArgs converts methodArgs to a string value if methodSig is an empty string.
+// We are calling a contract written with fallback pattern, which has no method signature.
 func preprocessArgs(methodSig string, methodArgs interface{}) (interface{}, error) {
-	if !strings.HasPrefix(methodSig, "0x") || len(methodSig) != 10 {
+	if methodSig != "" {
 		return methodArgs, nil
 	}
 
 	switch args := methodArgs.(type) {
 	case []interface{}:
-		if len(args) > 0 {
+		if len(args) == 1 {
 			argStr, isStrVal := args[0].(string)
 			if !isStrVal {
 				return nil, fmt.Errorf("failed to convert method arg \"%T\" to string", args[0])
@@ -105,7 +105,7 @@ func preprocessArgs(methodSig string, methodArgs interface{}) (interface{}, erro
 		}
 		return methodArgs, nil
 	case []string:
-		if len(args) > 0 {
+		if len(args) == 1 {
 			return args[0], nil
 		}
 		return methodArgs, nil
@@ -219,13 +219,17 @@ func encodeMethodArgsStrings(methodID []byte, methodSig string, methodArgs []str
 // contractCallMethodID calculates the first 4 bytes of the method
 // signature for function call on contract
 func contractCallMethodID(methodSig string) ([]byte, error) {
-	if strings.HasPrefix(methodSig, "0x") && len(methodSig) == 10 {
+	/*if strings.HasPrefix(methodSig, "0x") && len(methodSig) == 10 {
 		// method signature is already a 4 byte hex string
 		result, err := hex.DecodeString(methodSig[2:])
 		if err != nil {
 			return nil, err
 		}
 		return result, nil
+	}*/
+	if methodSig == "" {
+		// contract call without method signature (fallback pattern)
+		return []byte{}, nil
 	}
 
 	fnSignature := []byte(methodSig)

services/construction/contract_call_data_test.go

@@ -52,9 +52,9 @@ func TestConstruction_ContractCallData(t *testing.T) {
 			expectedResponse: "0x60d7a2780000000000000000000000000000000000000000000000000000000000000060000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000008626f6f6c20616263000000000000000000000000000000000000000000000000",
 		},
 		"happy path: method sig is hex string and args is a list of interface": {
-			methodSig:        "0xabcdef12",
-			methodArgs:       []interface{}{"34567890"},
-			expectedResponse: "0xabcdef1234567890",
+			methodSig:        "",
+			methodArgs:       []interface{}{"0xabcde12345"},
+			expectedResponse: "0xabcde12345",
 		},
 		"error: case string: invalid method args hex data": {
 			methodSig:     "attest((bytes32,(address,uint64,bool,bytes32,bytes,uint256)))",
@@ -102,29 +102,29 @@ func TestConstruction_preprocessArgs(t *testing.T) {
 				"0",
 				"0x"},
 		},
-		"happy path: method sig is hex string and args is nil": {
-			methodSig:        "0xabcdef12",
+		"happy path: method sig is empty and args is nil": {
+			methodSig:        "",
 			methodArgs:       nil,
 			expectedResponse: nil,
 		},
-		"happy path: method sig is hex string and args is a single string": {
-			methodSig:        "0xabcdef12",
-			methodArgs:       "34567890",
-			expectedResponse: "34567890",
+		"happy path: method sig is empty and args is a single string": {
+			methodSig:        "",
+			methodArgs:       "0x12345",
+			expectedResponse: "0x12345",
 		},
-		"happy path: method sig is hex string and args is a list of interface": {
-			methodSig:        "0xabcdef12",
-			methodArgs:       []interface{}{"34567890"},
-			expectedResponse: "34567890",
+		"happy path: method sig is empty and args is a list of interface": {
+			methodSig:        "",
+			methodArgs:       []interface{}{"0xabcde"},
+			expectedResponse: "0xabcde",
 		},
-		"happy path: method sig is hex string and args is a list of strings": {
-			methodSig:        "0xabcdef12",
-			methodArgs:       []string{"34567890"},
-			expectedResponse: "34567890",
+		"happy path: method sig is empty and args is a list of strings": {
+			methodSig:        "",
+			methodArgs:       []string{"0x1a2b3c"},
+			expectedResponse: "0x1a2b3c",
 		},
 		"unhappy path: args is a list of interface and cannot be converted to strings": {
-			methodSig:     "0xabcdef12",
-			methodArgs:    []interface{}{34567890},
+			methodSig:     "",
+			methodArgs:    []interface{}{34567},
 			expectedError: errors.New("failed to convert method arg \"int\" to string"),
 		},
 	}