Ethersjs - get ERC20 contract decimals

Question

I have the following:

import { ethers } from "ethers";
import { ws } from "../providers/node";
import abi from "../abi";

export default async (address: string) => {
    const tokenContract = new ethers.Contract(address, abi, ws);

    return {
        name: await tokenContract.name(),
        symbol: await tokenContract.symbol(),
        supply: await tokenContract.totalSupply(),
        decimals: await tokenContract.decimals(),
    };
};

abi is the standard erc20 abi found here: https://ethereumdev.io/abi-for-erc20-contract-on-ethereum/

{
    constant: true,
    inputs: [],
    name: "decimals",
    outputs: [
        {
            name: "",
            type: "uint8",
        },
    ],
    payable: false,
    stateMutability: "view",
    type: "function",
},

all these calls are fine except the last one for the decimals() function.

I keep receiving the following error: cannot estimate gas; transaction may fail or may require manual gas limit

I have tried setting a gas limit on the call like so:

await tokenContract.decimals({
    gasLimit: "750000",
});

but this again results in the same error.

Is anyone able to advise as to why this might be failing?

The contract address that I query is a valid ERC20 contract.

Answer 1

In general name, symbol and decimal are optional methods according to EIP-20, therefore you should be prepared to handle that these methods error or return invalid data.

There are also contracts that implement this differently (e.g. by returning bytes32 or triggering their fallback method), so if you want to be bulletproof you should add some checks to these calls.

an example for such a token contract is the "TheDAO" token: https://etherscan.io/address/0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413#code

Answer 2

The contract you try to query (0x1800b081333A08bc5faAbb19a51dfCa15C1dfF21) was compiled with ABIEncoderV2, so maybe etherjs has some problem working with ABIV1 used to call ABIV2 compiled contracts.

The definition for decimals is slightly different with V2, but also with other fields so this does not explain why you have the error on decimals only, but just give a try to this ABIV2 generated directly from the source code:

[
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "_wallet1",
                "type": "address"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "constructor"
    },
    {
        "anonymous": false,
        "inputs": [
            {
                "indexed": true,
                "internalType": "address",
                "name": "owner",
                "type": "address"
            },
            {
                "indexed": true,
                "internalType": "address",
                "name": "spender",
                "type": "address"
            },
            {
                "indexed": false,
                "internalType": "uint256",
                "name": "value",
                "type": "uint256"
            }
        ],
        "name": "Approval",
        "type": "event"
    },
    {
        "anonymous": false,
        "inputs": [
            {
                "indexed": true,
                "internalType": "address",
                "name": "previousOwner",
                "type": "address"
            },
            {
                "indexed": true,
                "internalType": "address",
                "name": "newOwner",
                "type": "address"
            }
        ],
        "name": "OwnershipTransferred",
        "type": "event"
    },
    {
        "anonymous": false,
        "inputs": [
            {
                "indexed": true,
                "internalType": "address",
                "name": "from",
                "type": "address"
            },
            {
                "indexed": true,
                "internalType": "address",
                "name": "to",
                "type": "address"
            },
            {
                "indexed": false,
                "internalType": "uint256",
                "name": "value",
                "type": "uint256"
            }
        ],
        "name": "Transfer",
        "type": "event"
    },
    {
        "inputs": [],
        "name": "_limitedbuys",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "owner",
                "type": "address"
            },
            {
                "internalType": "address",
                "name": "spender",
                "type": "address"
            }
        ],
        "name": "allowance",
        "outputs": [
            {
                "internalType": "uint256",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "spender",
                "type": "address"
            },
            {
                "internalType": "uint256",
                "name": "amount",
                "type": "uint256"
            }
        ],
        "name": "approve",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "account",
                "type": "address"
            }
        ],
        "name": "balanceOf",
        "outputs": [
            {
                "internalType": "uint256",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "decimals",
        "outputs": [
            {
                "internalType": "uint8",
                "name": "",
                "type": "uint8"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "spender",
                "type": "address"
            },
            {
                "internalType": "uint256",
                "name": "subtractedValue",
                "type": "uint256"
            }
        ],
        "name": "decreaseAllowance",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "dexPair",
        "outputs": [
            {
                "internalType": "address",
                "name": "",
                "type": "address"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "dexRouter",
        "outputs": [
            {
                "internalType": "contract IDexRouter",
                "name": "",
                "type": "address"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "spender",
                "type": "address"
            },
            {
                "internalType": "uint256",
                "name": "addedValue",
                "type": "uint256"
            }
        ],
        "name": "increaseAllowance",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "bool",
                "name": "value",
                "type": "bool"
            }
        ],
        "name": "limitedbuys",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "name",
        "outputs": [
            {
                "internalType": "string",
                "name": "",
                "type": "string"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "owner",
        "outputs": [
            {
                "internalType": "address",
                "name": "",
                "type": "address"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "renounceOwnership",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "symbol",
        "outputs": [
            {
                "internalType": "string",
                "name": "",
                "type": "string"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "totalSupply",
        "outputs": [
            {
                "internalType": "uint256",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "recipient",
                "type": "address"
            },
            {
                "internalType": "uint256",
                "name": "amount",
                "type": "uint256"
            }
        ],
        "name": "transfer",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "sender",
                "type": "address"
            },
            {
                "internalType": "address",
                "name": "recipient",
                "type": "address"
            },
            {
                "internalType": "uint256",
                "name": "amount",
                "type": "uint256"
            }
        ],
        "name": "transferFrom",
        "outputs": [
            {
                "internalType": "bool",
                "name": "",
                "type": "bool"
            }
        ],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "address",
                "name": "newOwner",
                "type": "address"
            }
        ],
        "name": "transferOwnership",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    },
    {
        "inputs": [],
        "name": "wallet1",
        "outputs": [
            {
                "internalType": "address",
                "name": "",
                "type": "address"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    }
]