Reconnect in event of failed ShardActions (#1255)

This removes a `let _ = ...` which was silently causing some resume failures to become permanent, causing the shard to crash the next time it attempted to use its (closed) WS client. This is replaced with code to trigger a further resume and/or reidentification attempt.

In the worst case, this will attempt one further resume before "promoting" the resume into a full reidentify. The `ShardQueuer` is then already responsible for repeated full reidentify attempts from that point on.

src/client/bridge/gateway/shard_runner.rs

@@ -136,8 +136,28 @@ impl ShardRunner {
                     return self.request_restart().await;
                 },
                 Some(other) => {
-                    #[allow(clippy::let_underscore_must_use)]
-                    let _ = self.action(&other).await;
+                    if let Err(e) = self.action(&other).await {
+                        debug!(
+                            "[ShardRunner {:?}] Reconnecting due to error performing {:?}: {:?}",
+                            self.shard.shard_info(),
+                            other,
+                            e
+                        );
+                        match self.shard.reconnection_type() {
+                            ReconnectType::Reidentify => return self.request_restart().await,
+                            ReconnectType::Resume => {
+                                if let Err(why) = self.shard.resume().await {
+                                    warn!(
+                                        "[ShardRunner {:?}] Resume failed, reidentifying: {:?}",
+                                        self.shard.shard_info(),
+                                        why
+                                    );
+
+                                    return self.request_restart().await;
+                                }
+                            },
+                        };
+                    }
                 },
                 None => {},
             }

src/gateway/mod.rs

@@ -161,6 +161,7 @@ pub enum InterMessage {
     Json(Value),
 }
 
+#[derive(Debug)]
 #[non_exhaustive]
 pub enum ShardAction {
     Heartbeat,
@@ -169,6 +170,7 @@ pub enum ShardAction {
 }
 
 /// The type of reconnection that should be performed.
+#[derive(Debug)]
 #[non_exhaustive]
 pub enum ReconnectType {
     /// Indicator that a new connection should be made by sending an IDENTIFY.