Man I am pulling my hair out one at a time! Can someone save me from days of googling and ending up with no further answer? All I want to know is how to trigger Uniswap or any AMM to call this function 'swapExactTokensForTokensSupportingFeeOnTransferTokens' when user wants to sell my token via the Uniswap/Pancakeswap/Sushiswap UI. How does uniswap know that my token takes fees and then call that fee function instead of the regular one? Where do I tell it to do that in my code?? Why is this so complicated 😤😤🤬🤬

I shared your mood friend

Pancakeswap SDK repo contains router.ts. The file contains swapCallParameters function that is called by the frontend (src/hooks/useSwapCallback.ts). Depending on there is fee or not

Guys, does anyone have a unit test on adding liquidity to a fork (bsc/eth)? I'm trying to do it and I get a TRANSFER_FROM error.

> The pair is created with no problem, I get wbnb from the mainnet to have balance on the main account, I approve the router but still get that error.

Yes this hook I've looked at through Uniswap github. After digging more into the frontend of uniswap it seems the trade.type needs to equal "EXACT_INPUT". I think the reason for that is that the input will be exact on input but after recalculating the reserves/balances after fees are take the output will be different. Either way this is the other function that sets the trade type and ultimately the correct feesontransfer function:

/**
* Constructs an exact in trade with the given amount in and route
* @param route route of the exact in trade
* @param amountIn the amount being passed in
*/
public static exactIn(route: Route, amountIn: CurrencyAmount, chainId: ChainId): Trade {
return new Trade(route, amountIn, TradeType.EXACT_INPUT, chainId)
}

And just to be clear I am no where closer to figuring out how UniswapV2 triggers the correct function call for tokens that require fees taken on them 😤

This is definitely an approval issue as I used to get the same error code many times and it was always something going wrong with my approve statement

I tried to approve everything and it returns the same error 😅

a clear walkthrough on uniswap v2 is helpful

https://ethereum.org/en/developers/tutorials/uniswap-v2-annotated-code/

my approvals

hmm not sure mate. Google addliquidity transferhelper: transfer_from_failed. It's quite common and lots of troubleshoots to sift through for you

Thanks Sam, before coming to ask the group I have checked from A to Z google, I don't ask for help at first

Thanks. I need to start at the bottom again and work my way up the mountain using a different path

I hear you. Sadly I am not really working with web3 yet. Mainly just testing solidity contracts and learning using remix so can't help you but good luck mate

No...the blog just explained each part of code..clearly...there won't be a different path mate

Yeah but I have been making assumptions on how uniswap works just from being a user but now I am reading that blog and it is telling me the control flow which I did not know before so for sure I can see maybe a different path here to approach the problem than what I was banging my head with these last few days. Hope that makes sense friend

Yeah👍

Thanks Sam dont worry ^^!

Do you find solution ?

do you have wbnb?

or just Bnb?

Below the button auto compile...switch on optimization

I impersonate the wbnb address to send to me 500 wbnb so my account have wbnb

What are you using is it ganache or hardhat?

Nope that's not possible as it is not a static function of those variables it is generated by abis and as they are based on abis tabnine/copilot cannot get them

The best way is to use them a few times till tabnine generates some variables based on your previous usages

That's how I do it 😂

Hardhat with bsc mainnet fork

change your wallet bal swap bnb for wbnb and then try ig Or why not try adding liq with bnb?

you refer to addLiquidityEth?

Yes

I've tried, I've tried some things too but the error is persistent.

How are you modifying your bnb bal?

I've tried alot of times and it works always

Im using the ETH bal as BNB im wrong?

I tried to have wbnb balance too

@Voidcoder maybe if because im using a fork? Im not running the uni/pancake router/factory through internal deploy

I can't under why you are doing so

which is your aim

Im trying to createPair, addLiquidity and test swaps on (Tests)

you could fork mainnet and test with pancake router no?

Yep i can interact with the router/factory without any problem

as you can see i impersonate the wbnb and use it without any problem, the problem is creating the pair and adding liquidity

here es some of the prints that i share here

I tried to send tokens to the liquidity new pair address and i get pancakeswap error input amount

At the first, You swap token to wbnb ?

No im not swapping at the moment, i createPair then i approve and later i tried to addLiquidity

Do you have X token and WBnB on acc?

yep

Or you have token in contract address ? And wbnb on your account?

You deploy token, mint to your account then create pair
Right?

I have token in my account and wbnb in my account

I am creating the pair in Js, not through the token contract.

😯