.getContractAddress() returning an incorrect address.

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Describe the bug I have a Contract (A) that creates a Contract (B).

// Creates a new ERC20 contract
function createERC20(
  string memory _name,
  string memory _symbol,
  uint _mintAmount
) external returns (address newToken) {
  newToken = address(
	new ERC20Token(_name, _symbol, address(this), msg.sender, _mintAmount)
  );
  emit TokenCreated(newToken, _name, _symbol);
}

In the frontend, when I try to run getContractAddress() using tx.from & tx.nonce, I get an address back, but it’s not the one that got created.

// Surprisingly this line returns the correct address BEFORE the contract is even accepted in MetaMask.
factoryContract.on('TokenCreated', e => console.log(e));

const tx = await factoryContract.createERC20(
  tokenName,
  tokenSymbol,
  mintAmount
);
// This returns an incorrect contract address.
const newTokenAddress = getContractAddress({
  from: tx.from,
  nonce: tx.nonce
});
await tx.wait();
			

Environment: Hardhat, MetaMask, Ethers.js, Next.js

[ricmoo]

Thanks! Glad to helps. 😃

I haven’t actually ever done this myself, but every address’ nonce is stored in the state trie, and should be accessible using provider.getTransactionCount(contractA.address).

Generally I would recommend emitting an event in your ContractA that indicates the new address created, since then the transaction receipt can be queried more reliably, otherwise you might compute the new B’s address and someone might front-run you and sneak in ahead of you create that contract.

Using create2 also gives more control over the address being created, which does not take the sending nonce into account. But emitting an event is still recommended, if possible. Obviously sometimes this isn’t possible, such as counterfactual instantiating where the contract wont be deployed for quite some time (if ever).

Let me know if that works. 😃

[ricmoo]

Are you trying to compute the address of contract A or contract B? For contract B you will need to use the nonce of contract A, not the EOA that sent the transaction.