shard: Separate state's cabinet, fix return bugs

This commit makes it so that all sharded state.State instances will have
its own cabinet store on construction. This ensures that when a State is
reconnected, a Ready event won't wipe the cabinet for all other states.

This commit also fixes a bug with the Shard() and FromGuildID() getters.

gateway/shard/manager.go

@@ -155,7 +155,7 @@ func (m *Manager) Shard(ix int) Shard {
 		return nil
 	}
 
-	return m.shards[ix]
+	return m.shards[ix].Shard
 }
 
 // FromGuildID returns the Shard and the shard ID for the guild with the given
@@ -165,7 +165,7 @@ func (m *Manager) FromGuildID(guildID discord.GuildID) (shard Shard, ix int) {
 	defer m.mutex.RUnlock()
 
 	ix = int(uint64(guildID>>22) % uint64(len(m.shards)))
-	return m.shards[ix], ix
+	return m.shards[ix].Shard, ix
 }
 
 // ForEach calls the given function on each shard from first to last. The caller

gateway/shard/shard.go

@@ -38,7 +38,7 @@ func NewGatewayShard(m *Manager, id *gateway.Identifier) *gateway.Gateway {
 
 // ShardState wraps around the Gateway interface to provide additional state.
 type ShardState struct {
-	Shard
+	Shard Shard
 	// This is a bit wasteful: 2 constant pointers are stored here, and they
 	// waste GC cycles. This is unavoidable, however, since the API has to take
 	// in a pointer to Identifier, not IdentifyData. This is to ensure rescales
@@ -55,7 +55,7 @@ func (state ShardState) ShardID() int {
 // OpenShards opens the gateways of the given list of shard states.
 func OpenShards(ctx context.Context, shards []ShardState) error {
 	for i, shard := range shards {
-		if err := shard.Open(ctx); err != nil {
+		if err := shard.Shard.Open(ctx); err != nil {
 			CloseShards(shards)
 			return errors.Wrapf(err, "failed to open shard %d/%d", i, len(shards)-1)
 		}
@@ -73,7 +73,7 @@ func CloseShards(shards []ShardState) error {
 
 	for i, gw := range shards {
 		if gw.Opened {
-			if err := gw.Close(); err != nil {
+			if err := gw.Shard.Close(); err != nil {
 				lastError = err
 			}
 

session/session.go

@@ -30,7 +30,6 @@ type Closed struct {
 }
 
 // NewShardFunc creates a shard constructor for a session.
-// Accessing any shard and adding a handler will add a handler for all shards.
 func NewShardFunc(f func(m *shard.Manager, s *Session)) shard.NewShardFunc {
 	return func(m *shard.Manager, id *gateway.Identifier) (shard.Shard, error) {
 		s := NewCustomShard(m, id)

state/state.go

@@ -22,29 +22,12 @@ var (
 	MaxFetchGuilds  uint = 100
 )
 
-// NewShardFunc creates a shard constructor that shares the same handler. The
-// given opts function is called everytime the State is created. If it doesn't
-// set a cabinet into the state, then a shared default cabinet is set instead.
+// NewShardFunc creates a shard constructor with its own state registry and
+// handlers. The given opts function is called everytime the State is created.
+// The user should initialize handlers and intents in the opts function.
 func NewShardFunc(opts func(*shard.Manager, *State)) shard.NewShardFunc {
-	var once sync.Once
-	var cab *store.Cabinet
-
 	return func(m *shard.Manager, id *gateway.Identifier) (shard.Shard, error) {
-		state := NewFromSession(session.NewCustomShard(m, id), nil)
-
-		if opts != nil {
-			opts(m, state)
-		}
-
-		if state.Cabinet == nil {
-			// Create the cabinet once; use sync.Once so the constructor can be
-			// concurrently safe.
-			once.Do(func() { cab = defaultstore.New() })
-
-			state.Cabinet = cab
-		}
-
-		return state, nil
+		return NewFromSession(session.NewCustomShard(m, id), defaultstore.New()), nil
 	}
 }