Why does contract event fire when no events have happened?

[adriandelgg]

Describe the bug
I'm using contract.on(); & whenever I reload the page it triggers the event being fired even though no event has happened yet. I thought the expected behavior was that it ONLY triggers when an event is fired?

Correct me if I'm wrong, but shouldn't it only fire if an event happens? Meaning that when you call contract.on(event, listener) it will listener passively but not trigger the listener until the event actually happens?

Reproduction steps

useEffect(() => {
function newToken(
   by: string,
   address: string,
   symbol: string
) {
   window.ethereum.request({
     method: 'wallet_watchAsset',
     params: {
        type: 'ERC20',
        options: {
           address,
           symbol,
           decimals: 18
        }
     }
   });
}
factoryContract.on('TokenCreated', newToken);
}, [factoryContract]);

Environment:
Hardhat, Ethers.js, Next.js/React

[ricmoo]

What is the event being shown? Keep in mind in v5 the events are scanned for starting in the current block, so if the current block has that event it will show up.

In v6 only future blocks will emit an event.

[adriandelgg]

What is the event being shown? Keep in mind in v5 the events are scanned for starting in the current block, so if the current block has that event it will show up.

In v6 only future blocks will emit an event.

Ah, I see. Is there a way to start using v6 already, or is it already out? If not, when does it release?

[ricmoo]

No, v6 is still just local on my computer. For v5, the best way to accomplish what you want above is:

provider.once("block", () => {
    factoryContract.on('TokenCreated', newToken);
});

That will start the event handler after the next block occurs.