PagedAsyncEnumerator's nextPage should return false if there are no more pages.

src/Discord.Net.Core/Utils/Paging/PagedEnumerator.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -13,9 +12,9 @@ namespace Discord
         private readonly ulong? _start;
         private readonly int? _count;
         private readonly Func<PageInfo, CancellationToken, Task<IReadOnlyCollection<T>>> _getPage;
-        private readonly Action<PageInfo, IReadOnlyCollection<T>> _nextPage;
+        private readonly Func<PageInfo, IReadOnlyCollection<T>, bool> _nextPage;
 
-        public PagedAsyncEnumerable(int pageSize, Func<PageInfo, CancellationToken, Task<IReadOnlyCollection<T>>> getPage, Action<PageInfo, IReadOnlyCollection<T>> nextPage = null,
+        public PagedAsyncEnumerable(int pageSize, Func<PageInfo, CancellationToken, Task<IReadOnlyCollection<T>>> getPage, Func<PageInfo, IReadOnlyCollection<T>, bool> nextPage = null,
             ulong? start = null, int? count = null)
         {
             PageSize = pageSize;
@@ -64,7 +63,10 @@ namespace Discord
                 _info.PageSize = _info.Remaining != null ? (int)Math.Min(_info.Remaining.Value, _source.PageSize) : _source.PageSize;
 
                 if (_info.Remaining != 0)
-                    _source?._nextPage(_info, data);
+                {
+                    if (!_source._nextPage(_info, data))
+                        _info.Remaining = 0;
+                }
 
                 return true;
             }

src/Discord.Net.Rest/Entities/Channels/ChannelHelper.cs

@@ -86,16 +86,17 @@ namespace Discord.Rest
                     if (info.Position != null)
                         args.RelativeMessageId = info.Position.Value;
                     var models = await client.ApiClient.GetChannelMessagesAsync(channel.Id, args, options).ConfigureAwait(false);
-                    return models.Select(x => RestMessage.Create(client, guild, x)).ToImmutableArray(); ;
+                    return models.Select(x => RestMessage.Create(client, guild, x)).ToImmutableArray();
                 },
                 nextPage: (info, lastPage) =>
                 {
+                    if (lastPage.Count != DiscordConfig.MaxMessagesPerBatch)
+                        return false;
                     if (dir == Direction.Before)
                         info.Position = lastPage.Min(x => x.Id);
                     else
                         info.Position = lastPage.Max(x => x.Id);
-                    if (lastPage.Count != DiscordConfig.MaxMessagesPerBatch)
-                        info.Remaining = 0;
+                    return true;
                 },
                 start: fromMessageId,
                 count: limit
@@ -196,9 +197,10 @@ namespace Discord.Rest
                 },
                 nextPage: (info, lastPage) =>
                 {
-                    info.Position = lastPage.Max(x => x.Id);
                     if (lastPage.Count != DiscordConfig.MaxMessagesPerBatch)
-                        info.Remaining = 0;
+                        return false;
+                    info.Position = lastPage.Max(x => x.Id);
+                    return true;
                 },
                 start: fromUserId,
                 count: limit

src/Discord.Net.Rest/Entities/Guilds/GuildHelper.cs

@@ -187,9 +187,10 @@ namespace Discord.Rest
                 },
                 nextPage: (info, lastPage) =>
                 {
-                    info.Position = lastPage.Max(x => x.Id);
                     if (lastPage.Count != DiscordConfig.MaxMessagesPerBatch)
-                        info.Remaining = 0;
+                        return false;
+                    info.Position = lastPage.Max(x => x.Id);
+                    return true;
                 },
                 start: fromUserId,
                 count: limit