feature: Fix #1280 Add NewsChannel Types (#1293)

* add News channel type

* remove (very outdated) todo

* add [Socket/Rest]NewsChannel types

* update TextChannel properties to include a Type optional parameter with validation

as of writing, this feature is still only available to verified guilds, which makes it impossible for testing.

* actually create the news channels when given the type

* throw NotSupportedException in News channel

throw a NotSupportedException whenever trying to use SlowModeInterval or anything related to overwrite permissions

* make RestNewsChannel throw NotSupportedException also

* remove the (untested) ability to change channel types

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

@@ -23,6 +23,7 @@ namespace Discord.Rest
         {
             switch (model.Type)
             {
+                case ChannelType.News:
                 case ChannelType.Text:
                 case ChannelType.Voice:
                     return RestGuildChannel.Create(discord, new RestGuild(discord, model.GuildId.Value), model);

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

@@ -15,7 +15,7 @@ namespace Discord.Rest
         private ImmutableArray<Overwrite> _overwrites;
 
         /// <inheritdoc />
-        public IReadOnlyCollection<Overwrite> PermissionOverwrites => _overwrites;
+        public virtual IReadOnlyCollection<Overwrite> PermissionOverwrites => _overwrites;
 
         internal IGuild Guild { get; }
         /// <inheritdoc />
@@ -34,6 +34,8 @@ namespace Discord.Rest
         {
             switch (model.Type)
             {
+                case ChannelType.News:
+                    return RestNewsChannel.Create(discord, guild, model);
                 case ChannelType.Text:
                     return RestTextChannel.Create(discord, guild, model);
                 case ChannelType.Voice:
@@ -79,7 +81,7 @@ namespace Discord.Rest
         /// <returns>
         ///     An overwrite object for the targeted user; <c>null</c> if none is set.
         /// </returns>
-        public OverwritePermissions? GetPermissionOverwrite(IUser user)
+        public virtual OverwritePermissions? GetPermissionOverwrite(IUser user)
         {
             for (int i = 0; i < _overwrites.Length; i++)
             {
@@ -96,7 +98,7 @@ namespace Discord.Rest
         /// <returns>
         ///     An overwrite object for the targeted role; <c>null</c> if none is set.
         /// </returns>
-        public OverwritePermissions? GetPermissionOverwrite(IRole role)
+        public virtual OverwritePermissions? GetPermissionOverwrite(IRole role)
         {
             for (int i = 0; i < _overwrites.Length; i++)
             {
@@ -115,7 +117,7 @@ namespace Discord.Rest
         /// <returns>
         ///     A task representing the asynchronous permission operation for adding the specified permissions to the channel.
         /// </returns>
-        public async Task AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options = null)
+        public virtual async Task AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options = null)
         {
             await ChannelHelper.AddPermissionOverwriteAsync(this, Discord, user, permissions, options).ConfigureAwait(false);
             _overwrites = _overwrites.Add(new Overwrite(user.Id, PermissionTarget.User, new OverwritePermissions(permissions.AllowValue, permissions.DenyValue)));
@@ -129,7 +131,7 @@ namespace Discord.Rest
         /// <returns>
         ///     A task representing the asynchronous permission operation for adding the specified permissions to the channel.
         /// </returns>
-        public async Task AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options = null)
+        public virtual async Task AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options = null)
         {
             await ChannelHelper.AddPermissionOverwriteAsync(this, Discord, role, permissions, options).ConfigureAwait(false);
             _overwrites = _overwrites.Add(new Overwrite(role.Id, PermissionTarget.Role, new OverwritePermissions(permissions.AllowValue, permissions.DenyValue)));
@@ -143,7 +145,7 @@ namespace Discord.Rest
         /// <returns>
         ///     A task representing the asynchronous operation for removing the specified permissions from the channel.
         /// </returns>
-        public async Task RemovePermissionOverwriteAsync(IUser user, RequestOptions options = null)
+        public virtual async Task RemovePermissionOverwriteAsync(IUser user, RequestOptions options = null)
         {
             await ChannelHelper.RemovePermissionOverwriteAsync(this, Discord, user, options).ConfigureAwait(false);
 
@@ -164,7 +166,7 @@ namespace Discord.Rest
         /// <returns>
         ///     A task representing the asynchronous operation for removing the specified permissions from the channel.
         /// </returns>
-        public async Task RemovePermissionOverwriteAsync(IRole role, RequestOptions options = null)
+        public virtual async Task RemovePermissionOverwriteAsync(IRole role, RequestOptions options = null)
         {
             await ChannelHelper.RemovePermissionOverwriteAsync(this, Discord, role, options).ConfigureAwait(false);
 

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

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Model = Discord.API.Channel;
+
+namespace Discord.Rest
+{
+    /// <summary>
+    ///     Represents a REST-based news channel in a guild that has the same properties as a <see cref="RestTextChannel"/>.
+    /// </summary>
+    [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
+    public class RestNewsChannel : RestTextChannel
+    {
+        internal RestNewsChannel(BaseDiscordClient discord, IGuild guild, ulong id)
+            :base(discord, guild, id)
+        {
+        }
+        internal new static RestNewsChannel Create(BaseDiscordClient discord, IGuild guild, Model model)
+        {
+            var entity = new RestNewsChannel(discord, guild, model.Id);
+            entity.Update(model);
+            return entity;
+        }
+        public override int SlowModeInterval => throw new NotSupportedException("News channels do not support Slow Mode.");
+        public override Task AddPermissionOverwriteAsync(IRole role, OverwritePermissions permissions, RequestOptions options = null)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+        public override Task AddPermissionOverwriteAsync(IUser user, OverwritePermissions permissions, RequestOptions options = null)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+        public override OverwritePermissions? GetPermissionOverwrite(IRole role)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+        public override OverwritePermissions? GetPermissionOverwrite(IUser user)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+        public override Task RemovePermissionOverwriteAsync(IRole role, RequestOptions options = null)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+        public override Task RemovePermissionOverwriteAsync(IUser user, RequestOptions options = null)
+        {
+            throw new NotSupportedException("News channels do not support Overwrite Permissions.");
+        }
+    }
+}

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

@@ -17,7 +17,7 @@ namespace Discord.Rest
         /// <inheritdoc />
         public string Topic { get; private set; }
         /// <inheritdoc />
-        public int SlowModeInterval { get; private set; } 
+        public virtual int SlowModeInterval { get; private set; } 
         /// <inheritdoc />
         public ulong? CategoryId { get; private set; }