What is the reasoning behind ethers.js choosing to have the return value of a function be an array that contains the value, rather than just the value itself

Question

What is the reasoning behind ethers.js choosing to have the return value of a function be an array that contains the value, rather than just the value itself

An issue arose with the test case below:

    it('should access MAX_COUNT', async () => {
        const maxCount = await myContract.functions.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

The test failed with this error message:

AssertionError: expected [ BigNumber { value: "64" } ] to equal 64

This code snippet represents a simplified version of the smart contract under testing:

// SPDX-License-Identifier: GPL-3.0
pragma solidity 0.8.17;

contract MyContract
{
    uint256 public constant MAX_COUNT = 64;
}

Questioning why the return value is displayed as

[ BigNumber { value: "64" } ]

instead of

BigNumber { value: "64" }

.

To provide context, this inquiry initially originated from an attempt to resolve this question: How to correctly import

@nomicfoundation/hardhat-chai-matchers

into hardhat project? ... However, it proved to be entirely unrelated.

typescript solidity ethers.js hardhat rootstock

Answer 1

Answer №1

This particular test is expected to fail:

    it('should retrieve MAX_COUNT', async () => {
        const maxCount = await multiSend.functions.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

On the contrary, this test is anticipated to succeed:

    it('should retrieve MAX_COUNT', async () => {
        const maxCount = await multiSend.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

Additionally, this test should also pass:

    it('should retrieve MAX_COUNT', async () => {
        const [maxCount] = await multiSend.functions.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

The key lies in understanding the documentation, particularly the distinction in return types when accessed through Contract.functions.XYZ() versus Contract.XYZ():

documentation for Contract.functions call

To summarize, Contract.XYZ() may return either Promise< any > or Promise< Result >; while Contract.functions.XYZ() consistently returns Promise< Result >

documentation for Result return type

The Result structure is intended for functions that can yield multiple values, hence the necessity for array destructuring.

Answer 2

This particular test is expected to fail:

    it('should retrieve MAX_COUNT', async () => {
        const maxCount = await multiSend.functions.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

On the contrary, this test is anticipated to succeed:

    it('should retrieve MAX_COUNT', async () => {
        const maxCount = await multiSend.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

Additionally, this test should also pass:

    it('should retrieve MAX_COUNT', async () => {
        const [maxCount] = await multiSend.functions.MAX_COUNT();
        expect(maxCount).to.equal(64);
    });

The key lies in understanding the documentation, particularly the distinction in return types when accessed through Contract.functions.XYZ() versus Contract.XYZ():

documentation for Contract.functions call

To summarize, Contract.XYZ() may return either Promise< any > or Promise< Result >; while Contract.functions.XYZ() consistently returns Promise< Result >

documentation for Result return type

The Result structure is intended for functions that can yield multiple values, hence the necessity for array destructuring.

What is the reasoning behind ethers.js choosing to have the return value of a function be an array that contains the value, rather than just the value itself

Answer №1

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