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A "buyer mints" NFT gallery running on Optimism |
Author: Austin Griffith****
Source code: https://github.com/scaffold-eth/scaffold-eth-examples/tree/optimistic-nft-dev-session
Intended audience: Intermediate
Topics: Scaffold-eth basics, NFTs, Layer 2, Optimism
git clone -b local-optimism https://github.com/scaffold-eth/scaffold-eth-examples.git local-optimism
cd local-optimism
yarn install
yarn start
in a second terminal window:
This requires Docker
Initiate the Optimism submodules...
cd scaffold-eth/docker/optimism-integration
git submodule init
git submodule update
Kick off the local chain, l2 & relay infrastructure (it kind of feels like a space-ship taking off)
cd scaffold-eth/docker/optimism-integration
make up
This branch has several contracts
YourContract.sol -> L2 An amended version of the basic YourContract that comes with scaffold-eth
ERC20.sol -> L1 An ERC20 contract with a mint(value) function that allows any user to mint themselve some tokens
L1ERC20Gateway.sol The example Optimism L1 Gateway contracts
L2DepositedERC20.sol The example Optimism L2 Deposited ERC20 contract
Kudos & thanks to the Optimistic Ethereum team whose erc20 example this benefited from!
in a third terminal window, generate a local account:
cd scaffold-eth
yarn generate
Send that account some ETH using the faucet from http://localhost:3000/ to fund the deployments
when the local nodes are up and running, deploy local contracts & attempt to go from L1 -> L2 and back again!
yarn deploy-oe
We import the following into our hardhat.config.js:
require('@eth-optimism/plugins/hardhat/compiler');
require('@eth-optimism/plugins/hardhat/ethers');
We created a dedicated oe-deploy.js, and split out our deploy() function in utils.js such that it can deploy on the EVM or the OVM.
oe-deploy.js instantiates using the specified network (currently localhost or kovan), deploys the above contracts, tying the bridged ERC20s, initialises the OVM_L2DepositedERC20, and then if demo == true, it demonstrates the L1->L2->L1 ERC20 bridging.
We use const { Watcher } = require('@eth-optimism/watcher') which monitors the relayed messages between L1 and L2.
Note that we are not able to use hardhat's usual accounts, so we use scaffold-eth's account generation...
There are three tabs:
- ETH bridging to Optimistic Eth (send yourself some L1 ETH with the faucet!) & send ETH on L1 & L2
- YourContract on L2
- OldEnglish ERC20 & Bridge contracts (make sure you approve the Gateway to bridge!)
- Is OE eompatible with hardhat config accounts? I had to instantiate in my deploy script
- Get a silent failure on L2 if I don't reset the nonces in Metamask
- Using OpenZeppelin contracts that import their Address.sol break:
@openzeppelin/contracts/utils/Address.sol:115:17: ParserError: OVM: SELFBALANCE is not implemented in the OVM. (We have no native ETH -- use deposited WETH instead!)
require(address(this).balance >= value, "Address: insufficient balance for call");
- Get a failure on OZ Safemint (https://docs.openzeppelin.com/contracts/3.x/api/token/erc721#ERC721-_safeMint-address-uint256-bytes-)
- Avoiding silent failures - the initial tx response doesn't give you an indication as to whether a transaction has succeeded or failed, you need to add:
await result.wait()
Which will then throw an error. This is different to the EVM, where the initial await transactionResponse will throw.
- Including a {value: amount} field in ovm .sol doesn't seem to throw?
- Time on L2 only updates when there is a transaction from L1 -> L2