Contract event listener is not firing when running hardhat tests on ethers v6

[6be709c0]

Version of Hardhat

2.15.0

What happened?

I'm running into the same issue as this one #1692 from 2 years ago with the correct modification in ethers v6 but the contract.on is not triggered.

 await new Promise(async (resolve) => {
      contractA.on("TokensMinted", (amount: BigNumber) => {
        // THIS LINE NEVER GETS HIT
        console.log("###########");
        resolve(true);
      });

      const contractTx: ContractTransaction = await contractA.mint(123);
      const contractReceipt: ContractReceipt = await contractTx.wait();

      for (const event of contractReceipt.logs!) {
        console.log(event.fragment.name, event.args[0].toString()); // TokensMinted 123
      }

      // Works
      //  contractA.emit("TokensMinted", 123);
    });

Contract:

// SPDX-License-Identifier: MIT
pragma solidity >=0.8.18;

contract ContractA {
    event TokensMinted(uint amount);

    function mint(uint amount) public {
        emit TokensMinted(amount);
    }
}

I'm adding the Promise to ensure to wait until the event is emitted.
From the receipt, the event is properly emitted, then it wait indefinitely because the event is never emitted.

If I emit the event manually using contractA.emit("TokensMinted", 123);, then I get the console.log and the promise is resolved.

Minimal reproduction steps

Repo to reproduce the issue easily: https://github.com/lescaudr/ethers-event-issue
pnpm install
pnpm compile
pnpm test

Search terms

No response

[fvictorio]

Thank you @lescaudr, I can confirm this. It's an important problem, I'll try to get it fixed asap.

[tevdoradze]

The same problem, .on is not working with hardhat node v2.12.3. Is there a version where it works?

[fvictorio]

@tevdoradze it should still work if you use ethers v5 (and the associated plugins: @nomicfoundation/hardhat-toolbox@2, @nomiclabs/hardhat-ethers@2 and @nomicfoundation/hardhat-chai-matchers@1)

[fvictorio]

Released in hardhat-ethers v3.0.3 🎉

[shaggyrec]

Released in hardhat-ethers v3.0.3 🎉

It still doesn't work in tests

[fvictorio]

@shaggyrec if you have reproduction steps, please open an issue about it.

[6be709c0]

I confirm it works perfectly @shaggyrec, see the branch "fixed" on https://github.com/lescaudr/ethers-event-issue where it's now using "hardhat": "^2.16.1". instead of 2.15.0

Thanks @fvictorio

[shaggyrec]

Yeah. Seems like working for your case and the standard hardhat Lock.sol contract (I rewrote the test with events to test events handling).

But for Patric Collins' tutorial updated to the latest versions it doesn't work.
https://github.com/shaggyrec/hardhat-smartcontract-lottery-ts/blob/main/test/unit/Raffle.test.ts#L163

I have no idea why.

[6be709c0]

You are right @shaggyrec, indexed events are not triggered, I created a new issue #4098. Also found that when triggering multiple events, only the first is triggered.

[tevdoradze]

if it doesn't work in your tests you are most likely not waiting long enough:

• Change the pollingInterval from 5s to 1s: yourcontract.provider.pollingInterval = 1;
• Resolve the test with done:

it("test", function (done) {
   ...
      yourcontract.on(
        ...,
        async (...) => {
          ...
          done();
        }
      );
      ...
  });

If you work with an upgradable contract you may need to add // @ts-ignore above the line where we change the pollingInterval

[6be709c0]

@tevdoradze polling interval is not the resolution here in ether v6. The bug has been confirmed, and is in progress

[Devankit2022]

update?

[6be709c0]

It has been fixed 3 weeks ago #4098 (comment)