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Account Abstraction (ERC-4337) — Hands-on lab

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6/8 — Account Abstraction (ERC-4337) — Hands-on lab

SimulateCraft userOps, sign them, run through a local bundler/entry point; flip paymaster rules to see reverts.

The root problem with conventional currency is all the trust that’s required to make it work.
— Satoshi Nakamoto

ObserveLog userOpHash, nonce, and paymaster data to debug acceptance/rejection.

{
  "sender": "0xWallet",
  "nonce": "0x0",
  "initCode": "0x",
  "callData": "0x1234...", // your call
  "callGasLimit": "0x100000",
  "verificationGasLimit": "0x80000",
  "preVerificationGas": "0x21000",
  "maxFeePerGas": "0x59682f0f",
  "maxPriorityFeePerGas": "0x3b9aca00",
  "paymasterAndData": "0x"
}

// Quick Foundry-style script to sign and send a userOp hash
UserOperation memory op = buildUserOp();
bytes32 opHash = entryPoint.getUserOpHash(op);
(uint8 v, bytes32 r, bytes32 s) = vm.sign(ownerPk, opHash);
op.signature = abi.encodePacked(r, s, v);
entryPoint.handleOps(userOps, payable(msg.sender));

Scripted submissions make it easy to toggle bad nonce/sig/paymaster data and watch validateUserOp fail or pass.

Steps

Generate a userOp with:CallData to a simple function; sign and submit to a local bundler.
Alter the nonce or:Signature and confirm validateUserOp reverts.
Attach a paymaster; set:A budget and see how maxGas/maxFee affect cost.
Batch two calls in:One userOp; confirm atomicity and gas accounting.
Log events for validation:Success/failure and paymaster sponsorship.

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