ABI Decoding Issue with go-ethereum: "Improperly Formatted Output" for Complex Tuple Array

[m-quigley]

I'm encountering an issue with decoding ABI data using go-ethereum's abi.Unpack or UnpackIntoInterface method. Here are the details:

Go Code Attempt:

type Route struct {
  From    common.Address
  To      common.Address
  Stable  bool
  Factory common.Address
}

type SwapExactTokensForTokensInput struct {
  AmountIn     *big.Int
  AmountOutMin *big.Int
  Routes       []Route
  To           common.Address
  Deadline     *big.Int
}

	abiJSON := `[
  {
    "inputs": [
      {
        "internalType": "uint256",
        "name": "amountIn",
        "type": "uint256"
      },
      {
        "internalType": "uint256",
        "name": "amountOutMin",
        "type": "uint256"
      },
      {
        "components": [
          {
            "internalType": "address",
            "name": "from",
            "type": "address"
          },
          {
            "internalType": "address",
            "name": "to",
            "type": "address"
          },
          {
            "internalType": "bool",
            "name": "stable",
            "type": "bool"
          },
          {
            "internalType": "address",
            "name": "factory",
            "type": "address"
          }
        ],
        "internalType": "struct IRouter.Route[]",
        "name": "routes",
        "type": "tuple[]"
      },
      {
        "internalType": "address",
        "name": "to",
        "type": "address"
      },
      {
        "internalType": "uint256",
        "name": "deadline",
        "type": "uint256"
      }
    ],
    "name": "swapExactTokensForTokens",
    "outputs": [
      {
        "internalType": "uint256[]",
        "name": "amounts",
        "type": "uint256[]"
      }
    ],
    "stateMutability": "nonpayable",
    "type": "function"
  }]`

	parsedABI, err := abi.JSON(strings.NewReader(abiJSON))
	if err != nil {
		log.Fatalf("Error parsing ABI: %v", err)
	}

	input := "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"

	var inputStruct SwapExactTokensForTokensInput
	if err := parsedABI.UnpackIntoInterface(&inputStruct, "swapExactTokensForTokens", common.FromHex(input)); err != nil {
		log.Fatalf("Error unpacking input: %v", err)
	}

Error Received:

Error unpacking input: abi: improperly formatted output: "\xcaȎ\xa9\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xc9\xf7\x8d(\x93\xe4\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xb4\xc0YZ\x86\xaa\x1c\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xa0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1ab(\xe2\xf0^\xe0\xc0\xe8\"\xbe\b$\x9c\x81[7F\x7f@\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00g`5\xba\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00B\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x06\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\b\"\xd3a3[M_5-\xac)<\xa4\x12\x8b[`_\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00B\rӁ\xb3\x1a\xeff\x83\xdbk\x90 \x84\xcb\x0f\xfe\xce@\xda" - Bytes: [202 200 142 169 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 201 247 141 40 147 228 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 180 192 89 90 134 170 28 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 160 0 0 0 0 0 0 0 0 0 0 0 0 26 98 40 226 240 94 224 192 232 34 190 8 36 156 129 91 55 70 127 64 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 103 96 53 186 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 66 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 128 8 34 211 97 51 91 77 95 53 45 172 41 60 164 18 139 91 96 95 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 66 13 211 129 179 26 239 102 131 219 107 144 32 132 203 15 254 206 64 218]

Steps Taken:

• Verified that the ABI matches the function signature in the smart contract.
• Checked that the hex input is correctly formatted and converted to bytes.
• Tested decoding in JavaScript with ethers.js, which works without issues.
• Tested decoding in https://lab.miguelmota.com/ethereum-input-data-decoder/example/, which works without issues.
• Ensured struct definitions match ABI specifications.

Question:

Can anyone identify why this decoding fails in Go, or is there a known issue with decoding such complex tuple arrays with go-ethereum? Any suggestions or fixes would be greatly appreciated.
I've used this same approach for decoding calldata hundreds of times, first time facing this issue

Additional Info:

go-ethereum version: 1.22
Go version: v1.14.12

any help would be hugely appreciated

[m-quigley]

the ABI is a subset of this CAs abi, if that helps at all
https://basescan.org/address/0xcf77a3ba9a5ca399b7c97c74d54e5b1beb874e43

[m-quigley]

also, slicing off the method selector

if err := parsedABI.UnpackIntoInterface(&inputStruct, "swapExactTokensForTokens", common.FromHex(input)[4:]); err != nil {

results in

2024/12/18 12:02:51 Error unpacking input: abi: cannot marshal in to go slice: offset 33000000000000000032 would go over slice boundary (len=320)

[m-quigley]

Found #26242 which is the same issue, never fully resolved. I have the same result, if I use method.Inputs.Unpack it works