Context I am trying to build a smart contract of a ERC20 token which comprehends the creation of the relative WETH/token pair on Uniswap V2.

Code The smart contract is as follow:

// SPDX-License-Identifier: MIT

pragma solidity ^0.8;

import "@openzeppelin/contracts/utils/Address.sol";
import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@uniswap/v2-core/contracts/interfaces/iUniswapV2Factory.sol";
import "@uniswap/v2-core/contracts/interfaces/iUniswapV2Pair.sol";
import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";
import "@uniswap/v2-periphery/contracts/interfaces/IWETH.sol";

contract BarnaTokenInu is Ownable, ERC20 {
using Address for address;

string constant __name = "BARNATOKENINU";
string constant __symbol = "BTI";
uint256 constant __decimals = 18;
uint256 constant initialInvestment = 0.002 * 10**18;
uint256 constant fractionForOwner = 20;
uint256 constant deadlineForLiquidityProvision = 20 * 60;
uint256 constant initialSupply = 1e9 * 10**__decimals;
address public router_address;
IUniswapV2Router02 public router;
IUniswapV2Factory public factory;
IUniswapV2Pair public pair;
address public liquidityPoolPair;
IWETH public iweth; // weth object interface
IERC20 public weth;

constructor(address _router_address) ERC20(__name, __symbol) {
    router_address = _router_address;
    router = IUniswapV2Router02(router_address);
    factory = IUniswapV2Factory(router.factory());
    liquidityPoolPair = factory.createPair(router.WETH(), address(this));
    pair = IUniswapV2Pair(liquidityPoolPair);
    iweth = IWETH(router.WETH());
    weth = IERC20(router.WETH());

    _approve(owner(), router_address, type(uint256).max);
    _approve(address(this), router_address, type(uint256).max);
    _mint(owner(), initialSupply); // mint token

function getPoolReserves() public view returns (uint112, uint112) {
    (uint112 reserveToken1, uint112 reserveToken2, ) = pair.getReserves();
    return (reserveToken1, reserveToken2);

function swapETHforWETH() public payable {
    iweth.deposit{value: msg.value}();
    weth.transfer(msg.sender, msg.value);

function addInitialLiquidity() public payable onlyOwner {
    weth.approve(router_address, initialInvestment);
    weth.approve(owner(), initialInvestment);
    router.addLiquidityETH{value: msg.value}(
        (initialSupply * fractionForOwner) / 100,
        (initialSupply * fractionForOwner) / 100,
        block.timestamp + deadlineForLiquidityProvision

The brownie main script from which the smart contract is deployed is as follows:

def deploy_token_contract(_account):
    if network.show_active() in LOCAL_DEVELOPMENT_ENVIRONMENTS:
        router = get_account(index=9)
        router = config["networks"][network.show_active()]["router_address"]
    return BarnaTokenInu.deploy(router, {"from": _account})

def main():
    account = get_account()
    contract = deploy_token_contract(account)
    contract.swapETHforWETH({"from": account, "value": 0.02 * 10**18})
    contract.addInitialLiquidity({"from": account, "value": 0.02 * 

Issue After the creation of the pair, I am not able to add liquidity to the pool, given that:

  • I have enough ETH in my account
  • I have made all the due approvals

I keep receiving the following error:

    VirtualMachineError: revert: TransferHelper: TRANSFER_FROM_FAILED

Full error trace:

    Transaction sent: 0x7ffd26ac40fe40b9eb211b94402b8ddcc60ebb311178755c457b393b34035f87
    Gas price: 0.0 gwei   Gas limit: 12000000   Nonce: 20
    BarnaTokenInu.addInitialLiquidity confirmed (TransferHelper: TRANSFER_FROM_FAILED)   
    Block: 15919924   Gas used: 87214 (0.73%)

    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\_cli\run.py", line 51, in main
    return_value, frame = run(
    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\project\scripts.py", line 110, in run
    return_value = f_locals[method_name](*args, **kwargs)
    File ".\scripts\main.py", line 30, in main
    contract.addInitialLiquidity({"from": account})
    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\network\contract.py", line 1861, in __call__
    return self.transact(*args)
    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\network\contract.py", line 1734, in transact
    return tx["from"].transfer(
    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\network\account.py", line 682, in transfer
    File "C:\Users\sma157555\AppData\Local\Programs\Python\Python310\lib\site- 
    packages\brownie\network\transaction.py", line 446, in _raise_if_reverted
    raise exc._with_attr(
    VirtualMachineError: revert: TransferHelper: TRANSFER_FROM_FAILED
    Trace step -1, program counter 3601:
    File "contracts/BarnaTokenInu.sol", lines 183-190, in BarnaTokenInu.addInitialLiquidity:

    weth.approve(router_address, initialInvestment);
    weth.approve(owner(), initialInvestment);
        (initialSupply * fractionForOwner) / 100,
        (initialSupply * fractionForOwner) / 100,
        block.timestamp + deadlineForLiquidityProvision

Is anybody able to detect the flaw?


I was unable to add liquidity because the add liquidity transaction sender is the contract from which the function is called...and there were no tokens on it...once I minted some tokens during contract deployment, everything worked


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