Discord gateway event `GUILD_MEMBERS_CHUNK` is treated as an `UnknownEvent` about serenity HOT 2 CLOSED

I think it's time to share a few findings, in case I'm not the only one trying to catch the fish or somebody in the future finds a similar issue.

I have started writing a workaround (at least, what I thought was one) to deserialize the event manually and somehow call the proper event handler, using the raw event handler as such:

pub struct RawHandler;

#[async_trait]
impl RawEventHandler for RawHandler {
    async fn raw_event(&self, ctx: Context, ev: Event) {
        match ev {
            Event::Unknown(unknown_event) if unknown_event.kind == "GUILD_MEMBERS_CHUNK" => {
                warn!("Using workaround for GUILD_MEMBERS_CHUNK event");
                handle_raw_guild_members_chunk(&ctx, unknown_event).await;
            },

            _ => { /* No-op */ }
        };
    }
}

async fn handle_raw_guild_members_chunk(ctx: &Context, event: UnknownEvent) {
    let event_str = serenity::json::to_string_pretty(&event).unwrap();
    println!("{}", event_str);
    println!("{:?}", event);

    let chunk_event = match serenity::json::from_value::<GuildMembersChunkEvent>(event.value) {
        Ok(chunk_event) => chunk_event,

        Err(why) => {
            error!("Deserialization error\n{:?}", why);
            return;
        }
    };
}

I have printed the stringified event and its deserialized representation to later check for discrepancies between Discord's documentation and the implementation of the data structures.

Then, I took this bit of code for a spin by compiling and running the program before continuing writing the code. The deserialization operation returns an error: Json(Error("invalid type: sequence, expected a map", line: 0, column: 0)).

When taking a closer look at Discord's documentation about the GUILD_MEMBERS_CHUNK event, the members property is an array. In Rust, that property is typed as a HashMap<UserId, Member>.

from serenity.

Thank you for diagnosing this. The culprit is #2287, which simplified the Deserialize impl for GuildMembersChunkEvent but forgot to make sure the hashmap was being constructed out of the array rather than being directly deserialized.

from serenity.