Querying Read-Only Methods but getting "cannot estimate gas"

[johndoe75]

I'm trying to query some read-only methods of token contracts on Binance Smart Chain such as number of decimals, totalSupply, …

    let metadataQuery = new ethers.Contract(
        contract,
        [
            'function name() external pure returns (string memory)',
            'function symbol() external pure returns (string memory)',
            'function decimals() external pure returns (uint8)',
            'function totalSupply() external view returns (uint)',
        ],
        account
    );

For some tokens this works just fine and I receive the result. For others I'm getting cannot estimate gas; transaction may fail or may require manual gas limit. I've tried to manually set the gasLimit like:

await metadataQuery.symbol({gasLimit: 36000});

but still get this error. According the documentation, querying read-only methods should be free as they can be computed by asking a single node. So I don't understand why I'm getting this error as I'm asking read-only methods. And I don't understand why I'm still getting the error when I manually define a gasLimit. Any suggestions how to fix this would be highly appreciated.

[zemse]

Some ERC20 tokens do not have the meta data functions, EIP20 says symbol() is optional, that's probably why your calls might be failing. Also for example MKR returns bytes32 instead of string memory (I guess this is because of how old Maker is, it was likely created before ERC20 spec was finalized). So you have to handle edge cases whenever you encounter a token that doesn't work in standard form.

[johndoe75]

Got it. Thanks for the explanation.

[crazydevlegend]

Thanks, @zemse . Actually I had the same issue and this really helped me out!