fix: don't delete rows from messages table when the associated member is deleted

PluralKit.API/Controllers/v2/DiscordControllerV2.cs

@@ -148,7 +148,7 @@ public class DiscordControllerV2: PKControllerBase
         if (msg == null)
             throw Errors.MessageNotFound;
 
-        var ctx = ContextFor(msg.System);
+        var ctx = msg.System == null ? LookupContext.ByNonOwner : ContextFor(msg.System);
         return msg.ToJson(ctx, APIVersion.V2);
     }
 }

PluralKit.Bot/Commands/Message.cs

@@ -51,7 +51,7 @@ public class ProxiedMessage
 
         var msg = await GetMessageToEdit(ctx);
 
-        if (ctx.System.Id != msg.System.Id)
+        if (ctx.System.Id != msg.System?.Id)
             throw new PKError("Can't edit a message sent by a different system.");
 
         var newContent = ctx.RemainderOrNull().NormalizeLineEndSpacing();
@@ -209,7 +209,7 @@ public class ProxiedMessage
             if (!showContent)
                 throw new PKError(noShowContentError);
 
-            if (message.System.Id != ctx.System.Id)
+            if (message.System?.Id != ctx.System.Id && message.Message.Sender != ctx.Author.Id)
                 throw new PKError("You can only delete your own messages.");
 
             await ctx.Rest.DeleteMessage(message.Message.Channel, message.Message.Mid);

PluralKit.Bot/Handlers/ReactionAdded.cs

@@ -128,7 +128,7 @@ public class ReactionAdded: IEventHandler<MessageReactionAddEvent>
         var system = await _repo.GetSystemByAccount(evt.UserId);
 
         // Can only delete your own message
-        if (msg.System.Id != system?.Id) return;
+        if (msg.System?.Id != system?.Id && msg.Message.Sender != evt.UserId) return;
 
         try
         {
@@ -170,6 +170,7 @@ public class ReactionAdded: IEventHandler<MessageReactionAddEvent>
         try
         {
             var dm = await _cache.GetOrCreateDmChannel(_rest, evt.UserId);
+            if (msg.Member != null)
                 await _rest.CreateMessage(dm.Id, new MessageRequest
                 {
                     Embed = await _embeds.CreateMemberEmbed(
@@ -202,6 +203,8 @@ public class ReactionAdded: IEventHandler<MessageReactionAddEvent>
         var requiredPerms = PermissionSet.ViewChannel | PermissionSet.SendMessages;
         if (member == null || !(await _cache.PermissionsFor(evt.ChannelId, member)).HasFlag(requiredPerms)) return;
 
+        if (msg.Member == null) return;
+
         var config = await _repo.GetSystemConfig(msg.System.Id);
 
         if (config.PingsEnabled)

PluralKit.Bot/Services/EmbedService.cs

@@ -355,13 +355,20 @@ public class EmbedService
 
         // Put it all together
         var eb = new EmbedBuilder()
-            .Author(new Embed.EmbedAuthor(msg.Member.NameFor(ctx),
+            .Author(new Embed.EmbedAuthor(msg.Member?.NameFor(ctx) ?? "(deleted member)",
-                IconUrl: msg.Member.AvatarFor(ctx).TryGetCleanCdnUrl()))
+                IconUrl: msg.Member?.AvatarFor(ctx).TryGetCleanCdnUrl()))
             .Description(content)
             .Image(showContent ? new Embed.EmbedImage(serverMsg?.Attachments?.FirstOrDefault()?.Url) : null)
             .Field(new Embed.Field("System",
-                msg.System.Name != null ? $"{msg.System.Name} (`{msg.System.Hid}`)" : $"`{msg.System.Hid}`", true))
+                msg.System == null
-            .Field(new Embed.Field("Member", $"{msg.Member.NameFor(ctx)} (`{msg.Member.Hid}`)", true))
+                    ? "*(deleted or unknown system)*"
+                    : msg.System.Name != null ? $"{msg.System.Name} (`{msg.System.Hid}`)" : $"`{msg.System.Hid}`"
+            , true))
+            .Field(new Embed.Field("Member",
+                msg.Member == null
+                    ? "*(deleted member)*"
+                    : $"{msg.Member.NameFor(ctx)} (`{msg.Member.Hid}`)"
+            , true))
             .Field(new Embed.Field("Sent by", userStr, true))
             .Timestamp(DiscordUtils.SnowflakeToInstant(msg.Message.Mid).ToDateTimeOffset().ToString("O"));
 

PluralKit.Bot/Services/LogChannelService.cs

@@ -44,7 +44,7 @@ public class LogChannelService
         var triggerChannel = await _cache.GetChannel(proxiedMessage.Channel);
 
         var system = await _repo.GetSystem(ctx.SystemId.Value);
-        var member = await _repo.GetMember(proxiedMessage.Member);
+        var member = await _repo.GetMember(proxiedMessage.Member!.Value);
 
         // Send embed!
         var embed = _embed.CreateLoggedMessageEmbed(trigger, hookMessage, system.Hid, member, triggerChannel.Name,

PluralKit.Core/Database/Migrations/24.sql

@@ -0,0 +1,10 @@
+-- schema version 24
+-- don't drop message rows when system/member are deleted
+
+alter table messages alter column member drop not null;
+alter table messages drop contstraint messages_member_fkey;
+alter table messages
+    add constraint messages_member_fkey
+    foreign key (member) references members(id) on delete set null;
+
+update info set schema_version = 24;

PluralKit.Core/Database/Repository/ModelRepository.Message.cs

@@ -29,9 +29,13 @@ public partial class ModelRepository
         FullMessage Mapper(PKMessage msg, PKMember member, PKSystem system) =>
             new() { Message = msg, System = system, Member = member };
 
+        var query = "select * from messages"
+            + " left join members on messages.member = members.id"
+            + " left join systems on members.system = systems.id"
+            + " where (mid = @Id or original_mid = @Id)";
+
         var result = await conn.QueryAsync<PKMessage, PKMember, PKSystem, FullMessage>(
-            "select messages.*, members.*, systems.* from messages, members, systems where (mid = @Id or original_mid = @Id) and messages.member = members.id and systems.id = members.system",
+            query, Mapper, new { Id = id });
-            Mapper, new { Id = id });
         return result.FirstOrDefault();
     }
 

PluralKit.Core/Dispatch/DispatchService.cs

@@ -133,7 +133,7 @@ public class DispatchService
         if (system.WebhookUrl == null)
             return;
 
-        var member = await repo.GetMember(newMessage.Member);
+        var member = await repo.GetMember(newMessage.Member!.Value);
 
         var fullMessage = new FullMessage
         {

PluralKit.Core/Models/PKMessage.cs

@@ -9,7 +9,7 @@ public class PKMessage
     public ulong Mid { get; set; }
     public ulong? Guild { get; set; } // null value means "no data" (ie. from before this field being added)
     public ulong Channel { get; set; }
-    public MemberId Member { get; set; }
+    public MemberId? Member { get; set; }
     public ulong Sender { get; set; }
     public ulong? OriginalMid { get; set; }
 }
@@ -17,8 +17,8 @@ public class PKMessage
 public class FullMessage
 {
     public PKMessage Message;
-    public PKMember Member;
+    public PKMember? Member;
-    public PKSystem System;
+    public PKSystem? System;
 
     public JObject ToJson(LookupContext ctx, APIVersion v)
     {
@@ -30,8 +30,8 @@ public class FullMessage
         o.Add("sender", Message.Sender.ToString());
         o.Add("channel", Message.Channel.ToString());
         o.Add("guild", Message.Guild?.ToString());
-        o.Add("system", System.ToJson(ctx, v));
+        o.Add("system", System?.ToJson(ctx, v));
-        o.Add("member", Member.ToJson(ctx, v: v));
+        o.Add("member", Member?.ToJson(ctx, v: v));
 
         return o;
     }