This guide explains how to use the L2ToL2CrossDomainMessenger to call a contract on chain B from chain A.
The full code snippet can be found here
supersim
// Using viem to transfer L2NativeSuperchainERC20 + +import { + http, + encodeFunctionData, + createWalletClient, + parseAbi, + defineChain, + publicActions, +} from "viem"; +import { privateKeyToAccount } from "viem/accounts"; +import { + publicActionsL2, + walletActionsL2, + extractMessageIdentifierFromLogs, +} from "@eth-optimism/viem"; +import { anvil } from "viem/chains"; + +// Define constants - L2NativeSuperchainERC20 contract address is the same on every chain +const L2_NATIVE_SUPERCHAINERC20_ADDRESS = + "0x61a6eF395d217eD7C79e1B84880167a417796172"; + +const L2_TO_L2_CROSS_DOMAIN_MESSENGER_ADDRESS = + "0x4200000000000000000000000000000000000023"; + +// account for 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266 +const account = privateKeyToAccount( + "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80", +); + +// Define chains +const opChainA = defineChain({ + ...anvil, + id: 901, + name: "OPChainA", + rpcUrls: { + default: { + http: ["http://127.0.0.1:9545"], + }, + }, +}); + +const opChainB = defineChain({ + ...anvil, + id: 902, + name: "OPChainB", + rpcUrls: { + default: { + http: ["http://127.0.0.1:9546"], + }, + }, +}); + +// Configure op clients +const opChainAClient = createWalletClient({ + transport: http(), + chain: opChainA, + account, +}) + .extend(walletActionsL2()) + .extend(publicActionsL2()) + .extend(publicActions); + +const opChainBClient = createWalletClient({ + transport: http(), + chain: opChainB, + account, +}) + .extend(walletActionsL2()) + .extend(publicActionsL2()) + .extend(publicActions); + +// ####### +// OP Chain A +// ####### +// 1. Mint 1000 `L2NativeSuperchainERC20` token + +const mintTxHash = await opChainAClient.writeContract({ + address: L2_NATIVE_SUPERCHAINERC20_ADDRESS, + abi: parseAbi(["function mint(address to, uint256 amount)"]), + functionName: "mint", + args: [account.address, 1000n], +}); + +await opChainAClient.waitForTransactionReceipt({ hash: mintTxHash }); + +// 2. Initiate sendERC20 tx +console.log("Initiating sendERC20 on OPChainA..."); +const sendERC20TxHash = await opChainAClient.writeContract({ + address: L2_NATIVE_SUPERCHAINERC20_ADDRESS, + abi: parseAbi([ + "function sendERC20(address _to, uint256 _amount, uint256 _chainId)", + ]), + functionName: "sendERC20", + args: [account.address, 1000n, BigInt(opChainB.id)], +}); + +const sendERC20TxReceipt = await opChainAClient.waitForTransactionReceipt({ + hash: sendERC20TxHash, +}); + +// 3. Grab the message identifier from the logs +const { id: messageIdentifier, payload: l2ToL2CrossDomainMessengerCalldata } = + await extractMessageIdentifierFromLogs(opChainAClient, { + receipt: sendERC20TxReceipt, + }); + +// ########## +// OP Chain B +// ########## +// 4. Execute the relayERC20 function on OPChainB +console.log("Building execute relayERC20 on OPChainB..."); +const executeArgs = await opChainBClient.buildExecuteL2ToL2Message({ + id: messageIdentifier, + target: L2_TO_L2_CROSS_DOMAIN_MESSENGER_ADDRESS, + message: l2ToL2CrossDomainMessengerCalldata, +}); + +console.log("Executing L2 to L2 message on OPChainB..."); + +const executeTxHash = await opChainBClient.executeL2ToL2Message(executeArgs); + +await opChainBClient.waitForTransactionReceipt({ + hash: executeTxHash, +}); + +// 5. Check balance on OPChainB +const balance = await opChainBClient.readContract({ + address: L2_NATIVE_SUPERCHAINERC20_ADDRESS, + abi: parseAbi(["function balanceOf(address) view returns (uint256)"]), + functionName: "balanceOf", + args: [account.address], +}); + +console.log(`Balance on OPChainB: ${balance}`); + +