Support async callbacks in SignalR typescript client

[sryarama]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

We have async listeners set up for onclose, onreconnecting, and onreconnected events, along with a logger to capture all SignalR messages. However, when an unhandled rejection occurs within the async listeners, it is not being passed back to the registered logger.

Expected Behavior

No response

Steps To Reproduce

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Exceptions (if any)

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.NET Version

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Anything else?

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[BrennanConroy]

Please show an example. We don't even know what client you're using.

[sryarama]

Here is the sample listener code.

hubConnection.onclose( async (error) => { if (isTokenValid) { throw new Error("Invalid token"); } else { await reconnect(); } });

Lets say if I don't have a valid token, I want to log an error in the telemetry. SignalR SDK is capturing the exception I throw above and not sending it through the logger I registered during initialization.

[BrennanConroy]

Ok so you're using the typescript library. The exception is being passed to the logger:

aspnetcore/src/SignalR/clients/ts/signalr/src/HubConnection.ts

Line 864 in 80ac2ff

this._logger.log(LogLevel.Error, `An onclose callback called with error '${error}' threw error '${e}'.`);

I'm guessing you didn't call configureLogging(logger) on the HubConnectionBuilder. But also, if you're explicitly throwing an exception just for it to be logged, why not just log instead of throwing.

[sryarama]

We registered the logger using configureLogging. And it is working as expected when I register the sync listeners like this hubConnection.onclose((error) => { });. Issue is only with async listeners hubConnection.onclose(async (error) => { });

About explicitly throwing, its not that simple in our case. For easy understanding I gave the example like that.

[BrennanConroy]

Oh I see, missed the fact that sync works and async doesn't. Async methods aren't currently supported for the callbacks. See the method signature:
public onclose(callback: (error?: Error) => void): void
If you used a linter in typescript you might see warnings/errors when passing an async method to onclose. https://typescript-eslint.io/rules/no-misused-promises/

Obviously I don't know your code and how much control you have, but wrapping anything passed to onclose(...) in a try {} catch{} would fix your issue.