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.

[adriandelgg]

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.

Awesome, thank you! It works👍

When does v6 come out? Super excited for it!

[sebastiandine]

I am still getting the previous event, even when I use provider.once("block"). Only difference to the example above is, that I am using an event filter instead of a string.

[mkaya13]

Hi @sebastiandine I am experiencing the same issue. I am getting the previous event. Did you find a solution?

[AlexisN94]

I'm also experiencing this issue. The .once("block", ...) trick didn't fix it. Version 5.7.2

[mkaya13]

Hi @AlexisN94 I am experiencing the same issue. I am getting the previous event. Did you find a solution?

[ricmoo]

This should no longer be an issue and was fixed 2 years ago. Can you provide reproduction steps or additional information?