Invalid states should not emit events, they should revert.

[3esmit]

Events are meant to be used to update the user view when relevant state changes happen.

When using events to signal errors in transaction setup, this is a waste of gas and don't give proper user feedback until the transaction is minted (of course it can be mitigated by checking before, but the checks are made more difficult with errors as events).

Examples:

https://github.com/status-im/community-dapp/blob/7836a7692981b6796fa9c9bf0ae0d5f8cce14496/packages/contracts/contracts/VotingContract.sol#L56C58-L56C58

community-dapp/packages/contracts/contracts/FeaturedVotingContract.sol

Line 227 in 7836a76

emit NotEnoughToken(votes[i].community, votes[i].voter);

community-dapp/packages/contracts/contracts/FeaturedVotingContract.sol

Line 50 in 7836a76

event AlreadyVoted(bytes community, address voter);

Instead, error handling should be used https://docs.soliditylang.org/en/v0.8.20/control-structures.html#error-handling-assert-require-revert-and-exceptions

When a error is thrown, the DApp can detect and handle the error, before the transaction is submitted.