Unexpected behavior if staticCall returns an empty array

[leduythuccs]

Ethers Version

6.3.0

Search Terms

abi, empty array, decoder

Describe the Problem

If a staticCall returns an empty array (let's call it arr). The arr.map(...).length will have the length of 1, which is not correct.

I think it has something to do with the Result class here.

Code Snippet

import { ethers } from 'ethers';
// =======

const provider = new ethers.JsonRpcProvider('https://rpc.ankr.com/eth');
const contract = new ethers.Contract(
  '0xcbC72d92b2dc8187414F6734718563898740C0BC',
  [
    'function rewardIndexesStored() external view returns (uint256[] memory indexes)',
  ],
  {
    provider,
  },
);

const indexes = await contract.rewardIndexesStored.staticCall(); // an empty array
const mappedIndexes = indexes.map((index) => index.toString()); // should be an empty array

console.log('pre map length:', indexes.length); // 0
console.log('post map length:', mappedIndexes.length); // 1

console.log('pre map:', indexes); // []
console.log('post map:', mappedIndexes); // [0]

Contract ABI

['function rewardIndexesStored() external view returns (uint256[] memory indexes)']

Errors

No response

Environment

Ethereum (mainnet/ropsten/rinkeby/goerli), node.js (v12 or newer)

Environment (Other)

No response

[leduythuccs]

Another way to reproduce this is just simply use the Result:

import { Result } from 'ethers';

const emptyArray = new Result();
const mappedEmptyArray = emptyArray.map((index) => index.toString());
console.log('pre map length:', emptyArray.length); // 0
console.log('post map length:', mappedEmptyArray.length); // 1

console.log('pre map:', emptyArray); // []
console.log('post map:', mappedEmptyArray); // [0]

Output:

pre map length: 0
post map length: 1
pre map: Result(0) []
post map: Result(1) [ 0 ]

[ricmoo]

Confirmed as a bug. Fixed locally and I'll get a fix published shortly.

[ricmoo]

Fixed in v6.4.0.

Let me know if you have any more issues.

Thanks! :)