Help: log whether the bot is a member of the server when the DM fails

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

internal/commands/help/help.go

@@ -1,6 +1,7 @@
 package help
 
 import (
+	"fmt"
 	"log"
 	"unicode/utf8"
 
@@ -139,8 +140,8 @@ func HelpHandler(s *discordgo.Session, i *discordgo.InteractionCreate) {
 		// when "no mutual guilds" appears for someone who is in a server with
 		// the bot: a command run through a user install, or in a server the bot
 		// isn't actually a member of, has no shared server for Discord to see.
-		log.Printf("help: DM not possible, showing it here (guild %q, context %d, installs %v): %v",
+		log.Printf("help: DM not possible, showing it here (guild %q, context %d, installs %v, %s): %v",
-			i.GuildID, i.Context, i.AuthorizingIntegrationOwners, err)
+			i.GuildID, i.Context, i.AuthorizingIntegrationOwners, botMembership(s, i.GuildID), err)
 		note := "I couldn't DM you (your DMs may be off), so here it is."
 		_, _ = s.InteractionResponseEdit(i.Interaction, &discordgo.WebhookEdit{Content: &note, Embeds: &list})
 		return
@@ -161,3 +162,21 @@ func sendByDM(s *discordgo.Session, userID string, list []*discordgo.MessageEmbe
 	}
 	return nil
 }
+
+// botMembership says whether the bot is really a member of the server, which
+// is what Discord means by "mutual guilds". A server where the app was added
+// with only the applications.commands scope runs slash commands fine but has
+// no bot user in it.
+func botMembership(s *discordgo.Session, guildID string) string {
+	if s == nil || s.State == nil || s.State.User == nil {
+		return "bot user unknown"
+	}
+	inCache := false
+	if g, err := s.State.Guild(guildID); err == nil && g != nil {
+		inCache = true
+	}
+	if _, err := s.GuildMember(guildID, s.State.User.ID); err != nil {
+		return fmt.Sprintf("bot is NOT a member of that server (in gateway cache: %v): %v", inCache, err)
+	}
+	return fmt.Sprintf("bot is a member of that server (in gateway cache: %v)", inCache)
+}