hardhat-tracer

hardhat-tracer 🕵️

Allows you to see events, calls and storage operations when running your tests.

• hardhat-tracer 🕵️
  • Installation
  • Usage
    • Test
    • Trace
    • Calldata decoder
    • Address name tags
    • State overrides
    • Chai util

Installation

Step 1: Install the package

npm i hardhat-tracer

Step 2: Add to your hardhat.config.js file

require("hardhat-tracer");

Usage

Test

npx hardhat test --traceError # prints calls for failed txs
npx hardhat test --fulltraceError # prints calls and storage ops for failed txs
npx hardhat test --trace # prints calls for all txs
npx hardhat test --fulltrace # prints calls and storage ops for all txs

npx hardhat test --v    # same as --traceError
npx hardhat test --vv   # same as --fulltraceError
npx hardhat test --vvv  # same as --trace
npx hardhat test --vvvv # same as --fulltrace

# specify opcode
npx hardhat test --v --opcodes ADD,SUB   # shows any opcode specified for only failed txs
npx hardhat test --vvv --opcodes ADD,SUB # shows any opcode specified for all txs

You can just enable trace some code snippet in your tests:

hre.tracer.enable = true;
await myContract.doStuff(val2);
hre.tracer.enable = false;

Trace

You can trace a mainnet transaction and ABIs/artifacts in your project will be used to decode the internal message calls.

npx hardhat trace --hash 0xTransactionHash # works if mainnet fork is on
npx hardhat trace --hash 0xTransactionHash --rpc https://url # must be archive node

Calldata decoder

If you are just looking for a quick decode of calldata, return data or Solidity"s Custom Error:

$ npx hardhat decode --data 0x095ea7b300000000000000000000000068b3465833fb72a70ecdf485e0e4c7bd8665fc45ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
ERC20.approve(spender=0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45, amount=115792089237316195423570985008687907853269984665640564039457584007913129639935)


$ npx hardhat decode --data 0x3850c7bd --returndata 0x000000000000000000000000000000000000000000024d0fa9cd4ba6ff769172fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffcdea1000000000000000000000000000000000000000000000000000000000000a244000000000000000000000000000000000000000000000000000000000000ff78000000000000000000000000000000000000000000000000000000000000ffff00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001

IUniswapV3Pool(0x0000000000000000000000000000000000000000).slot0() => (sqrtPriceX96: 2781762795090269932261746, tick: -205151, observationIndex: 41540, observationCardinality: 65400, observationCardinalityNext: 65535, feeProtocol: 0, unlocked: true)

Address name tags

You can set display names / name tags for unknown addresses by adding new entry to hre.tracer.nameTags object in your test cases, see following example:

hre.tracer.nameTags[this.arbitrager.address] = "Arbitrager";

or can be set in hardhat config

tracer: {
  nameTags: {
    "0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266": "Hunter",
    [someVariable]: "MyContract",
  },
},

State overrides

These state overrides are applied when the EthereumJS/VM is created inside hardhat.

tracer: {
  stateOverrides: {
    "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2": {
      storage: {
        "0": 100,
        "0x1abf42a573070203916aa7bf9118741d8da5f9522f66b5368aa0a2644f487b38": 0,
      },
      bytecode: "0x30FF",
      balance: parseEther("2"),
      nonce: 2
    },
  },
},

Chai util

Allows to add a test case to check whether last tx did an internal message call.

expect(hre.tracer.lastTrace()).to.have.messageCall(
  await contract.populateTransaction.getData(),
  {
    returnData: defaultAbiCoder.encode(["uint"], ["1234"]),
    from: otherContract.address,
    isDelegateCall: true,
    isStaticCall: true,
    isSuccess: true,
  }
);