Provide old presence data from the cache on presence update (#2852)

examples/e10_gateway_intents/src/main.rs

@@ -16,7 +16,12 @@ impl EventHandler for Handler {
 
     // As the intents set in this example, this event shall never be dispatched.
     // Try it by changing your status.
-    async fn presence_update(&self, _ctx: Context, _new_data: Presence) {
+    async fn presence_update(
+        &self,
+        _ctx: Context,
+        _old_data: Option<Presence>,
+        _new_data: Presence,
+    ) {
         println!("Presence Update");
     }
 

src/cache/event.rs

@@ -32,7 +32,7 @@ use crate::model::event::{
     VoiceChannelStatusUpdateEvent,
     VoiceStateUpdateEvent,
 };
-use crate::model::gateway::ShardInfo;
+use crate::model::gateway::{Presence, ShardInfo};
 use crate::model::guild::{Guild, GuildMemberFlags, Member, MemberGeneratedFlags, Role};
 use crate::model::id::ShardId;
 use crate::model::user::{CurrentUser, OnlineStatus};
@@ -394,11 +394,13 @@ impl CacheUpdate for MessageUpdateEvent {
 }
 
 impl CacheUpdate for PresenceUpdateEvent {
-    type Output = ();
+    type Output = Presence;
 
-    fn update(&mut self, cache: &Cache) -> Option<()> {
+    fn update(&mut self, cache: &Cache) -> Option<Presence> {
         if let Some(guild_id) = self.presence.guild_id {
             if let Some(mut guild) = cache.guilds.get_mut(&guild_id) {
+                let old = guild.presences.get(&self.presence.user.id).cloned();
+
                 // If the member went offline, remove them from the presence list.
                 if self.presence.status == OnlineStatus::Offline {
                     guild.presences.remove(&self.presence.user.id);
@@ -425,6 +427,8 @@ impl CacheUpdate for PresenceUpdateEvent {
                         });
                     }
                 }
+
+                return old;
             }
         }
 

src/client/dispatch.rs

@@ -319,9 +319,10 @@ fn update_cache_with_event(
             presences: event.presences.into_vec(),
         },
         Event::PresenceUpdate(mut event) => {
-            update_cache!(cache, event);
+            let old_data = if_cache!(event.update(cache));
 
             FullEvent::PresenceUpdate {
+                old_data,
                 new_data: event.presence,
             }
         },

src/client/event_handler.rs

@@ -315,11 +315,12 @@ event_handler! {
 
     /// Dispatched when a user's presence is updated (e.g off -> on).
     ///
-    /// Provides the presence's new data.
+    /// Provides the presence's new data, as well as the old presence data if the
+    /// cache feature is enabled and the data is available.
     ///
     /// Note: This event will not trigger unless the "guild presences" privileged intent is enabled
     /// on the bot application page.
-    PresenceUpdate { new_data: Presence } => async fn presence_update(&self, ctx: Context);
+    PresenceUpdate { old_data: Option<Presence>, new_data: Presence } => async fn presence_update(&self, ctx: Context);
 
     /// Dispatched upon startup.
     ///