Nullable slash command arguments throw DSharpPlus.Commands.Exceptions.ArgumentParseException

[ecrocombe]

Summary

Nullable slash command arguments in DSharpPlus.Commands fire DiscordClient.CommandErrored event under certain conditions with "DSharpPlus.Commands.Exceptions.ArgumentParseException: Argument Converter for type DSharpPlus.Entities.DiscordChannel was unable to parse the argument."

What version of the library are you using?

v5.0.0-nightly (make sure you are using the latest nightly!)

What .NET version are you using? Make sure to use the latest patch release for your major version.

.NET 8.0

Operating System

Ubuntu 22.04

Reproduction Steps

Using the below as an example, specify gameserver and the optional prefix and suffix arguments, but do not specify voice-channel.

[Command("onlinechannel")]
[Description("Assign a voice channel to display the number online")]
[RequirePermissions(botPermissions: DiscordPermissions.None, userPermissions: DiscordPermissions.ManageGuild)]
public async Task SetOnlineChannel
(
SlashCommandContext ctx,

[Parameter("gameserver")]
[Description("Choose the gameserver to modify")]
[SlashAutoCompleteProvider<GameserverAutocompleteHandler>]
int gameserverId,

[Parameter("voice-channel")]
[Description( "Choose the voice channel to rename with the player count")]
[SlashChannelTypes(DiscordChannelType.Voice)]
DiscordChannel? voiceChannel = null,

[Parameter("prefix")]
[Description("The text to display before the number of players in the voice channel name")]
string? prefix = null,

[Parameter("suffix")]
[Description("The text to display after the number of players in the voice channel name")]
string? suffix = null
)

Trace Logs

[17:57:55 VRB] Discord CommandErrored: Message: Argument Converter for type DSharpPlus.Entities.DiscordChannel was unable to parse the argument. : StackTrace: null

Exceptions or other error messages

17:57:55 WRN] Discord CommandErrored
DSharpPlus.Commands.Exceptions.ArgumentParseException: Argument Converter for type DSharpPlus.Entities.DiscordChannel was unable to parse the argument.

Anything else you'd like to share

No response

[ecrocombe]

see @akiraveliara comment in discord (https://discord.com/channels/379378609942560770/1094835363475886163/1234923321947066398)

i am very suspicious of https://github.com/DSharpPlus/DSharpPlus/blob/master/DSharpPlus.Commands/Processors/BaseCommandProcessor/BaseCommandProcessor.cs#L209, fwiw

[ecrocombe]

possible duplicate of #1843