GetNextMessageAsync returns null Results

Summary

After using the MessageExtension.GetNextMessageAsync method (with or without parameters) on a DiscordMessage object, accessing the returned Results property causes NullReferenceException.

Details

The length of time it took for the NRE to occur from the point GetNextMessageAsync is called is equivalent to the time specified in the interactivity configuration timeout. The NRE occurs even if you haven’t sent anything into the respective channel.

Steps to reproduce

1. Send a message into a channel,
2. Use the GetNextMessageAsync method on the message object,
3. Enter a random word,
4. Try to access the Results property and it should be null.

[OoLunar]

Confirmed bug, not because of the NRE but because GetNextMessageAsync isn’t properly getting the next message causing the method to timeout (as seen in InteractivityResult<DiscordMessage>.TimedOut). Here’s a repro:

InteractivityResult<DiscordMessage> nextMessage = await context.Message.GetNextMessageAsync();
if (nextMessage.TimedOut)
{
    await context.RespondAsync("Timed out.");
    return;
}
else
{
    await context.RespondAsync($"Message by {nextMessage.Result.Author.Username}:\n{nextMessage.Result.Content}");
}

Unofficially assigning @DWaffles if they wish to take up the issue

[zontreck]

It’s the timing out that is the issue, the code never gets executed. At least it didn’t when I was debugging it and trying to find the exact source. @OoLunar mentioned this in a above post too.

Dec 5, 2022 6:12:11 PM Velvet @.***>:

Doing some debugging, it seems everything is registered correctly. The MatchRequest is successfully registered to the ConcurrentHashSet _matchrequests property in the EventWaiter class, the predicate is filled with the correct variables and the timeout occurs as expected.

What isn’t expected is that EventWaiter.HandleEvent isn’t executed until the _matchrequests variable is empty (which is when the match request has timed out and is removed)

Looking at the code, I can’t see how this would happen? https://github.com/DSharpPlus/DSharpPlus/blob/545b9b28664788a7bfbce85062577036c653a4ab/DSharpPlus.Interactivity/EventHandling/EventWaiter.cs#L112-L134

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