Lesson 13: depositing WETH in Aave through aaveBorrorw.js

[ManuWeb3]

Hi all,

In aaveBorrow.js snippet below, while depositing Weth into Aave, why we used AMOUNT variable in await lendingPool.deposit(wethTokenAddress, AMOUNT, deployer, 0) when AMOUNT contains 0.1 ETH and Not Weth tokens ?

Why shouldn't we use wethBalance instead that has 0.1 WETH tokens, that we got in getWeth.js script, snippet below ?

And, if we're using AMOUNT variable only, then what was the purpose of wethBalance variable in the first place ?

aaveBorrow.js

const {getWeth, AMOUNT} = require("../scripts/getWeth")         
const {getNamedAccounts, ethers} = require("hardhat")

async function main() {

    await getWeth()                                    
    const {deployer} = await getNamedAccounts()         
    const lendingPool = await getLendingPool(deployer)
    const wethTokenAddress = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"
    await approve(wethTokenAddress, lendingPool.address, AMOUNT, deployer)     
    console.log("Depositing now...")
    
    await lendingPool.deposit(wethTokenAddress, AMOUNT, deployer, 0)    
    
    console.log("Deposited!!")
}

getWeth.js

const { ethers, getNamedAccounts, network } = require("hardhat")
const { networkConfig } = require("../helper-hardhat-config")

const AMOUNT = ethers.utils.parseEther("0.1")

async function getWeth() {
    const { deployer } = await getNamedAccounts()
    const iWeth = await ethers.getContractAt(
        "IWeth",
        networkConfig[network.config.chainId].wethToken,
        deployer
    )
    const txResponse = await iWeth.deposit({
        value: AMOUNT,
    })
    await txResponse.wait(1)
    
    const wethBalance = await iWeth.balanceOf(deployer)
    
    console.log(`Got ${wethBalance.toString()} WETH`)
}

module.exports = { getWeth, AMOUNT }

[othaime-en]

Hey @ManuWeb3 the getWeth() function allowed us to programmatically deposit ETH into the WETH contract and get back WETH right? Well... creating the function was a simple demonstration of how to achieve that and it was a good functionality too. However, for us to interact with the deposit() function of the lendingPool contract we only need the amount in wei form not in WETH. Checkout this section of the documentation to understand it more.
So in as much as the getWeth() function was really useful, we didn't need it in this scenario.

[ManuWeb3]

Hi @othaime-en , thanks for explaining.

we only need the amount in wei form not in WETH looks correct as per the documentation link you posted.

But then, if it's just the unit wei that matters, what exactly is the purpose of wethTokenAddress in the deposit function:

await lendingPool.deposit(wethTokenAddress, AMOUNT, deployer, 0)``` 

I mean to ask:
In the Production environment as well, can't we just pass wethTokenAddress along with some ETH and Not WETH as it's just '''wei''' that matters??

Secondly, if it's just about wei, then why this description mandates us to use WETHGateway while depositing any native currency (apart from ERC20):

I'm not able to connect all the dots here.

[ManuWeb3]

hey @othaime-en , after further working it out, I believe I connected the dots and saw the missing links in my understanding.

So, as far as I undestand, the wethTokenAddress (in case of deposit()) OR daiAddress (in case of borrow()) is actually the asset and the amount irrespective of the asset-type has to be expressed in wei while calling both deposit() and borrow()

We did not use the WETHGateway and instead used WETH9.sol smart contract to deposit ETH and get back equivalent WETH.

That means, using AMOUNT in aaveBorrow.js for deposit() , we're only concerned with the wei amount and not the type of the asset, as you already explained.

Did I understand correct ?

Secondly, a quick question:
You said "So in as much as the getWeth() function was really useful, we didn't need it in this scenario."

Are you sure, we don't need getWeth() because I believe we do need and have used getWeth() here as we did not use WETHGateway to deposit our native 0.1 ETH.

So, your " we didn't need it in this scenario." is the last dot I'm trying to make sense of.

[othaime-en]

Hey @ManuWeb3 to explain the "we didn't need it" part, we've learned that the deposit function only supports ERC20 tokens hence the need to have them in WETH right? In the lendingPool.deposit() documentation, we see that we the first parameter needed is the address of the asset we want to deposit. And since we can only deposit WETH, we pass in the address of the WETH token (This is the same address we used in our getWeth() function to convert our ETH to WETH), and the amount it WEI.
And if you remember, in our approve function await approve(wethTokenAddress, lendingPool.address, AMOUNT, deployer) We approved the lending pool to deposit funds into the wethTokenAddress on our behalf right? So what this means is that the .deposit() function does everything we did with getWeth() under the hood, gets the WETH tokens and deposits them for us.

[ManuWeb3]

Hey @othaime-en , thanks again for taking out your time to explain this to me.

From what I understood in the first place:
When we approved lendingPool.address to spend AMOUNT of WETH tokens on behalf of deployer, that approval got possible only because deployer already had WETH tokens as his balance, that he got from getWeth.

Now:
Had deployer not obtained WETH from getWeth, was this approval still possible ?

From your reasoning above, I understand that this approval was still possible (even when deployer had no WETH balance) because deposit() is anyway getting WETH from wethTokenAddress contract.

Is this exactly what you're trying to say ?
OR I still misunderstood something here ?

[othaime-en]

Hey @ManuWeb3 good question. The deployer needs to have a weth balance for this to all work. That's actually why we started our main function by calling the getWeth() function. Remember how to get the WETH tokens into our wallet we imported them by copying and pasting the wethTokenAddress into our wallet? yeah this follows the same principles, like we create weth tokens and give lendingPool the permission to use those weth tokens.

[ManuWeb3]

Noted. All good!!

I always had this 1 question but never bothered to ask in the 'Discussions'.

WETH9.sol has no function / code to send WETH token to the address right when msg.sender deposits ETH to it.

It's deposit() function (below) just updates the balanceOf[msg.sender] but does not transfer any WETH to the deployer by itself.

Is that the reason we had to manually copy - paste this contract's address to our wallet and import the WETH tokens ??

function deposit() public payable {
        balanceOf[msg.sender] += msg.value;
        Deposit(msg.sender, msg.value);