gateway: Separate Ready to ReadyEventExtras

This commit separates the undocumented fields of Ready to
ReadyEventExtras. Realistically, this is never an issue for bots, but it
might cripple non-bot users when Discord makes breaking changes to the
API.

This change allows Ready to still be unmarshaled even when the
undocumented fields cannot be unmarshaled. It also adds a new json.Raw
field that allows the whole Ready event to be unmarshaled differently.

This new ReadyEventExtras is also no longer marshaled as part of Ready.
Instead, none of its field will be present. Although this is a breaking
change, it solely concerns non-bot APIs, so it's acceptable.

gateway/events.go

@@ -1,18 +1,22 @@
 package gateway
 
 import (
-	"encoding/json"
 	"errors"
 	"strconv"
 	"strings"
 
 	"github.com/diamondburned/arikawa/v3/discord"
+	"github.com/diamondburned/arikawa/v3/utils/json"
 	"github.com/diamondburned/arikawa/v3/utils/json/option"
 	"github.com/diamondburned/arikawa/v3/utils/ws"
 )
 
 //go:generate go run ../utils/cmd/genevent -o event_methods.go
 
+// ReadyEventKeepRaw, if true, will make the gateway keep a copy of the raw JSON
+// body that makes up the Ready event. This is useful for non-bots.
+var ReadyEventKeepRaw = false
+
 // Event is a type alias for ws.Event. It exists for convenience and describes
 // the same event as any other ws.Event.
 type Event ws.Event
@@ -688,20 +692,52 @@ type ReadyEvent struct {
 		Flags discord.ApplicationFlags `json:"flags"`
 	} `json:"application"`
 
-	// Undocumented fields
+	// Bot users need not concern with what's in here. This field is only
+	// unmarshaled, not marshaled.
+	ReadyEventExtras `json:"-"`
+}
 
-	UserSettings      *UserSettings          `json:"user_settings,omitempty"`
-	ReadStates        []ReadState            `json:"read_state,omitempty"`
-	UserGuildSettings []UserGuildSetting     `json:"user_guild_settings,omitempty"`
-	Relationships     []discord.Relationship `json:"relationships,omitempty"`
-	Presences         []discord.Presence     `json:"presences,omitempty"`
+func (r *ReadyEvent) UnmarshalJSON(b []byte) error {
+	type raw ReadyEvent
+	if err := json.Unmarshal(b, (*raw)(r)); err != nil {
+		return err
+	}
 
-	FriendSuggestionCount int      `json:"friend_suggestion_count,omitempty"`
-	GeoOrderedRTCRegions  []string `json:"geo_ordered_rtc_regions,omitempty"`
+	// Optionally unmarshal ReadyEventExtras.
+	if !r.User.Bot {
+		r.ExtrasDecodeError = json.Unmarshal(b, &r.ReadyEventExtras)
+	}
+
+	if ReadyEventKeepRaw {
+		r.ReadyEventExtras.RawEventBody = append([]byte(nil), b...)
+	}
+
+	return nil
 }
 
 // Ready subtypes.
 type (
+	// ReadyEventExtras contains undocumented fields pertaining to the Ready
+	// event. This is the only event that receives this special treatment,
+	// because it's the one with the most undocumented things.
+	ReadyEventExtras struct {
+		UserSettings      *UserSettings          `json:"user_settings,omitempty"`
+		ReadStates        []ReadState            `json:"read_state,omitempty"`
+		UserGuildSettings []UserGuildSetting     `json:"user_guild_settings,omitempty"`
+		Relationships     []discord.Relationship `json:"relationships,omitempty"`
+		Presences         []discord.Presence     `json:"presences,omitempty"`
+
+		FriendSuggestionCount int      `json:"friend_suggestion_count,omitempty"`
+		GeoOrderedRTCRegions  []string `json:"geo_ordered_rtc_regions,omitempty"`
+
+		// RawEventBody is the raw JSON body for the Ready event. It is only
+		// available if ReadyEventKeepRaw is true.
+		RawEventBody json.Raw
+		// ExtrasDecodeError will be non-nil if there was an error decoding the
+		// ReadyEventExtras.
+		ExtrasDecodeError error
+	}
+
 	// ReadState is a single ReadState entry. It is undocumented.
 	ReadState struct {
 		ChannelID        discord.ChannelID `json:"id"`