INSUFFICIENT_OUTPUT_AMOUNT error

[yuichiroaoki]

I don't know how this error happened, but some people got this error when they change the config.

[trancee]

Do you know what config was changed? Because I am not sure about that. But what I did is to make sure the arbitrage opportunity is higher before executing the transaction. I guess that the opportunity is changing quite quickly and while the transaction is running, the opportunity was already lost because it was too slow to execute.

[yuichiroaoki]

I thought this error happened when you fail to borrow a loan token from dodo.

it("should be reverted with `INSUFFICIENT_INPUT_AMOUNT` when the bot set a wrong dodo pool and the contract can't borrow tokens.", async () => {
    await expect(
        Flashloan.dodoFlashLoan({
            flashLoanPool: dodoV2Pool.WMATIC_USDT,
            loanAmount: getBigNumber(1, 6),
            firstRoutes: [{
                path: [erc20Address.USDC, erc20Address.DAI],
                router: uniswapRouter.quickswap,
            }],
            secondRoutes: [{
                path: [erc20Address.DAI, erc20Address.USDC],
                router: uniswapRouter.quickswap
            }],
        }, { gasLimit: 1000000 })
    ).to.be.revertedWith("UniswapV2Library: INSUFFICIENT_INPUT_AMOUNT");
});

https://github.com/yuichiroaoki/poly-flash/blob/6d29dac77bedf2871eda23ab875b9f4843a993ab/test/errorMsg.test.ts#L37-L53

In this scenario, the contract will try to borrow USDC, but it can't borrow USDC from dodoV2Pool.WMATIC_USDT. The contract checks if the loan token is a base token of the dodo pool, and if not it borrow a quote token of the pool, so the contract would borrow USDT (quote token of dodoV2Pool.WMATIC_USDT).

I should have checked if the quote token is the loan token as well.

https://github.com/yuichiroaoki/poly-flash/blob/6d29dac77bedf2871eda23ab875b9f4843a993ab/contracts/Flashloan.sol#L51-L66

But it could be a different reason, I'm just guessing.

I will update the contract to check the dodo pool before executing flashloan and to make it clear.

ref. https://docs.uniswap.org/protocol/concepts/V3-overview/swaps#safety-checks https://ethereum.stackexchange.com/questions/90241/why-insufficient-output-amount

[trancee]

Thank you for looking into this issue. What you have tested is the INPUT amount, but my issue was about the OUTPUT amount. Can you make sure both are tested?

[yuichiroaoki]

Sure. I opened an issue on that.

https://github.com/yuichiroaoki/poly-flash/issues/4