Unused Event

Property	Value
Rule Code	NTX13
Severity	Warning

Background

Events are an essential part of smart contract development for monitoring on-chain activity. Defining events that are never emitted represents dead code and may indicate missing functionality.

Purpose

This rule detects events that are defined in the contract but never emitted via log statements.

Example

# Non-compliant code
event Transfer:
    sender: indexed(address)
    receiver: indexed(address)
    amount: uint256

event Approval:  # This event is never used
    owner: indexed(address)
    spender: indexed(address)
    amount: uint256

@external
def transfer(to: address, amount: uint256):
    # Only Transfer event is emitted
    log Transfer(msg.sender, to, amount)

# Compliant code
event Transfer:
    sender: indexed(address)
    receiver: indexed(address)
    amount: uint256

event Approval:
    owner: indexed(address)
    spender: indexed(address)
    amount: uint256

@external
def transfer(to: address, amount: uint256):
    log Transfer(msg.sender, to, amount)

@external
def approve(spender: address, amount: uint256):
    log Approval(msg.sender, spender, amount)  # Now Approval is used