smart contract how link libraries to child contract under factory pattern

Question

I am trying to create a factory and I can not find a way to link libraries to the child contract. I am trying to create a contract factory that create child contracts. the problem is that the child contract use a library and I just don't know how to link the deployed library to the contract created in runtime.

I am using truffle: Truffle v5.4.13 (core: 5.4.13) Solidity - 0.8.7 (solc-js) Node v10.15.3 Web3.js v1.5.3 The error is

Error: Cannot create instance of MetaCoin; no code at address 0x0a9b3Cab26fC5bd045E572555f1cB073A50Ad8a0

This is the code:

SafeMath.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.4;

/**
* @title SafeMath
* @dev Unsigned math operations with safety checks that revert on error
*/
library SafeMath {
    /**
    * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) public pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;
        return c;
    }

    /**
    * @dev Adds two unsigned integers, reverts on overflow.
    */
    function add(uint256 a, uint256 b) public pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);
        return c;
    }
}

MetaCoinFactory.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.4;

import "@openzeppelin/contracts/proxy/Clones.sol";

import "./MetaCoin.sol";

contract MetaCoinFactory {

    event UsersContractCreated(address);    
    address immutable tokenImplementation;

    constructor(){
    tokenImplementation = address(new MetaCoin());
    }

    function createToken() public returns (address) {
    address clone = Clones.clone(tokenImplementation);
    MetaCoin(clone).initialize(msg.sender);
        emit UsersContractCreated(clone);
    return clone;
    }
}

MetaCoin.sol

// SPDX-License-Identifier: GPL-3.0
pragma solidity ^0.8.4;

import {SafeMath} from "./SafeMath.sol";

contract MetaCoin {
    mapping (address => uint) public balances;
    bool private initialized;

    function initialize(address owner) public {
        require(!initialized, "Contract instance has already been initialized");
        balances[owner] = 100;
    }

    function sendCoin(address receiver, uint amount) public {
        balances[msg.sender] = SafeMath.sub(balances[msg.sender], amount);
        balances[receiver] = SafeMath.add(balances[receiver], amount);
    }

    function getBalance() public view returns (uint){
        return balances[msg.sender];
    }   
}

migration/2_deploy_contracts.js

const SafeMath = artifacts.require("SafeMath");
const MetaCoin = artifacts.require("MetaCoin");
const MetaCoinFactory = artifacts.require("MetaCoinFactory");

module.exports = async function(deployer) {
  await deployer.deploy(SafeMath);
  await deployer.link(SafeMath, [MetaCoinFactory, MetaCoin]);
  await deployer.deploy(MetaCoinFactory);
};

test/metacoinFactory.js

const { expect } = require('chai');

// Import utilities from Test Helpers
const { BN, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
const MetaCoinFactory = artifacts.require("MetaCoinFactory");
const MetaCoin = artifacts.require("MetaCoin");
const SafeMath = artifacts.require("SafeMath");

const mode = process.env.MODE;

contract("MetaCoinFactory", accounts => {

  it("should create contract and emit event", async () => {
    const metaCoinFactoryInstance = await MetaCoinFactory.deployed();
    const user = accounts[1];

    let result = await metaCoinFactoryInstance.createToken({ from: user });
    expectEvent(result, 'UsersContractCreated');
  });

  it("should get the address of the child contract", async () => {
    const metaCoinFactoryInstance = await MetaCoinFactory.deployed();
    const user = accounts[1];
    let address = await metaCoinFactoryInstance.createToken.call({ from: user });
    console.log(address);
    expect(address).contains("0x");
  });

  it("should get balance child the contract", async () => {
    const metaCoinFactoryInstance = await MetaCoinFactory.deployed();
    const user = accounts[1];
    let address = await metaCoinFactoryInstance.createToken.call({ from: user });
    const metaCoinInstance = await MetaCoin.at(address);
      // in here I get the error
    let balance = metaCoinInstance.getBalance({ from: user });
    expect(parseInt(balance)).to.be.equal(100);
  });
});

Error

Error: Cannot create instance of MetaCoin; no code at address 0x0a9b3Cab26fC5bd045E572555f1cB073A50Ad8a0

That was the allocated address of the child contract that was returned.

Thanks in advance

Answer 1

This is the correct way to link the library to the child contract. The problem I was having was related to the line

 let address = await metaCoinFactoryInstance.createToken.call({ from: user})

Since it is a transaction, I should use send(). The last truffle version doesn't have the send() function.. It should call the function instead that will return the transaction object. Sorry for the rookie error.