Added PublishAsync to Messages.

src/Discord.Net.Core/Entities/Messages/IUserMessage.cs

@@ -57,6 +57,15 @@ namespace Discord
         /// </returns>
         Task UnpinAsync(RequestOptions options = null);
 
+        /// <summary>
+        ///     Publish this message when executed in a News Channel.
+        /// </summary>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents the asynchronous operation for publishing this message.
+        /// </returns>
+        Task PublishAsync(RequestOptions options = null);
+
         /// <summary>
         ///     Transforms this message's text into a human-readable form by resolving its tags.
         /// </summary>

src/Discord.Net.Rest/DiscordRestApiClient.cs

@@ -695,6 +695,15 @@ namespace Discord.API
             var ids = new BucketIds(channelId: channelId);
             await SendAsync("POST", () => $"channels/{channelId}/typing", ids, options: options).ConfigureAwait(false);
         }
+        public async Task PublishAsync(ulong channelId, ulong messageId, RequestOptions options = null)
+        {
+            Preconditions.NotEqual(channelId, 0, nameof(channelId));
+            Preconditions.NotEqual(messageId, 0, nameof(messageId));
+            options = RequestOptions.CreateOrClone(options);
+
+            var ids = new BucketIds(channelId: channelId);
+            await SendAsync("POST", () => $"channels/{channelId}/messages/{messageId}/crosspost", ids, options: options).ConfigureAwait(false);
+        }
 
         //Channel Permissions
         public async Task ModifyChannelPermissionsAsync(ulong channelId, ulong targetId, ModifyChannelPermissionsParams args, RequestOptions options = null)

src/Discord.Net.Rest/Entities/Messages/MessageHelper.cs

@@ -44,8 +44,10 @@ namespace Discord.Rest
             };
             return await client.ApiClient.ModifyMessageAsync(msg.Channel.Id, msg.Id, apiArgs, options).ConfigureAwait(false);
         }
+
         public static Task DeleteAsync(IMessage msg, BaseDiscordClient client, RequestOptions options)
             => DeleteAsync(msg.Channel.Id, msg.Id, client, options);
+
         public static async Task DeleteAsync(ulong channelId, ulong msgId, BaseDiscordClient client,
             RequestOptions options)
         {
@@ -115,6 +117,7 @@ namespace Discord.Rest
         {
             await client.ApiClient.AddPinAsync(msg.Channel.Id, msg.Id, options).ConfigureAwait(false);
         }
+
         public static async Task UnpinAsync(IMessage msg, BaseDiscordClient client,
             RequestOptions options)
         {
@@ -240,6 +243,7 @@ namespace Discord.Rest
 
             return tags.ToImmutable();
         }
+
         private static int? FindIndex(IReadOnlyList<ITag> tags, int index)
         {
             int i = 0;
@@ -253,6 +257,7 @@ namespace Discord.Rest
                 return null; //Overlaps tag before this
             return i;
         }
+
         public static ImmutableArray<ulong> FilterTagsByKey(TagType type, ImmutableArray<ITag> tags)
         {
             return tags
@@ -260,6 +265,7 @@ namespace Discord.Rest
                 .Select(x => x.Key)
                 .ToImmutableArray();
         }
+
         public static ImmutableArray<T> FilterTagsByValue<T>(TagType type, ImmutableArray<ITag> tags)
         {
             return tags
@@ -279,5 +285,14 @@ namespace Discord.Rest
                 return MessageSource.Bot;
             return MessageSource.User;
         }
+
+        public static Task PublishAsync(IMessage msg, BaseDiscordClient client, RequestOptions options)
+            => PublishAsync(msg.Channel.Id, msg.Id, client, options);
+
+        public static async Task PublishAsync(ulong channelId, ulong msgId, BaseDiscordClient client,
+            RequestOptions options)
+        {
+            await client.ApiClient.PublishAsync(channelId, msgId, options).ConfigureAwait(false);
+        }
     }
 }

src/Discord.Net.Rest/Entities/Messages/RestMessage.cs

@@ -165,7 +165,7 @@ namespace Discord.Rest
         IReadOnlyCollection<IEmbed> IMessage.Embeds => Embeds;
         /// <inheritdoc />
         IReadOnlyCollection<ulong> IMessage.MentionedUserIds => MentionedUsers.Select(x => x.Id).ToImmutableArray();
-       
+
         /// <inheritdoc />
         public IReadOnlyDictionary<IEmote, ReactionMetadata> Reactions => _reactions.ToDictionary(x => x.Emote, x => new ReactionMetadata { ReactionCount = x.Count, IsMe = x.Me });
 

src/Discord.Net.WebSocket/Entities/Messages/SocketUserMessage.cs

@@ -123,7 +123,7 @@ namespace Discord.WebSocket
                 model.Content = text;
             }
         }
-        
+
         /// <inheritdoc />
         /// <exception cref="InvalidOperationException">Only the author of a message may modify the message.</exception>
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
@@ -150,5 +150,13 @@ namespace Discord.WebSocket
         
         private string DebuggerDisplay => $"{Author}: {Content} ({Id}{(Attachments.Count > 0 ? $", {Attachments.Count} Attachments" : "")})";
         internal new SocketUserMessage Clone() => MemberwiseClone() as SocketUserMessage;
+
+        public async Task PublishAsync(RequestOptions options = null)
+        {
+            if (Channel.GetType() == typeof(SocketNewsChannel))
+            {
+                await MessageHelper.PublishAsync(this, Discord, options);
+            }
+        }
     }
 }