watchContractEvent log args types narrowing fail #3767
Description
Check existing issues
- I checked there isn't already an issue for the bug I encountered.
Viem Version
2.31.4
Current Behavior
When using watchContractEvent from PublicClient without specifying an eventName, the type inference for log.args includes unnecessary union types (Record<string, unknown> and readonly unknown[]) even after narrowing with a condition like log.eventName === "CampaignCreated".
The type of log.args remains a union type:
args: Record<string, unknown> | readonly unknown[] | {
campaignId?: bigint | undefined;
creator?: `0x${string}` | undefined;
}
Expected Behavior
After checking log.eventName === "CampaignCreated", TypeScript should narrow the type of log.args to only the specific event args type:
{
campaignId?: bigint | undefined;
creator?: `0x${string}` | undefined;
}
Steps To Reproduce
publicClient.watchContractEvent({
abi: CampaignManagerAbi,
address: "0x0000...,
pollingInterval: 5000,
onError: (e) => {
console.log('[Listener] Error', e);
},
onLogs: async (logs) => {
if (logs.length === 0) return;
const promises = logs.map(async (log) => {
if (log.eventName === 'CampaignCreated') {
const { creator } = log.args; // Type error here, creator not in type
}
});
},
});
Link to Minimal Reproducible Example
No response
Anything else?
Workaround 1
Specifying eventName: 'CampaignCreated' resolves the type issue, but this limits the ability to listen for multiple events in a single watcher.
Typescript Version: 5.8.3
Using Nest JS