DiscordClient Initalization throws ArgumentOutOfRangeException when config has a message cache size but no intents for messages

Created by: Soyvolon

Summary

The constructor for DiscordClient checks for a message cache size and then test for intents, but if Guild Messages or Direct Messages are not specified in the intents it calls new RingBugger<DiscordMessage>(0); which will always throw a ArgumentOutOfRangeException.

Details

.NET Core 3.1 D#+ Nightly-00725 (Latest from master branch as of 9/23/2020 10:00 EST)

Without DiscordIntents.GuildMessages or DiscordIntents.DirectMessages, new RingBuffer<DiscordMessage>(0); is called and fails the if(size <= 0) check that prevents negative buffers, causing the bot to crash.

        public DiscordClient(DiscordConfiguration config)
            : base(config)
        {
            // . . .
                if (intents.HasValue)
                    this.MessageCache = intents.Value.HasIntent(DiscordIntents.GuildMessages) || intents.Value.HasIntent(DiscordIntents.DirectMessages)
                        ? new RingBuffer<DiscordMessage>(this.Configuration.MessageCacheSize)
                        : new RingBuffer<DiscordMessage>(0); // This will always throw an error.
         // . . .
        }

        public RingBuffer(int size)
        {
            if (size <= 0) // This throw will always be called if 
                                // Guild Messages or Direct Messages is not specified.
                throw new ArgumentOutOfRangeException(nameof(size), "Size must be positive.");
          // . . .
        }

Steps to reproduce

Run the DSharpPlus test bot with intents and a message cache larger than 0, as long as the intents do not include DiscordIntents.GuildMessages or DiscordIntents.DirectMessages

Notes

I would recommend to either keep the RingBuffer as null if the right intents are not passed, or throw a more detailed error for the user.