Backport: Guild#createChannel (#2145)

* Backport: Guild#createChannel

* this should not return a buffer

src/client/ClientDataResolver.js

@@ -11,6 +11,7 @@ const Channel = require('../structures/Channel');
 const GuildMember = require('../structures/GuildMember');
 const Emoji = require('../structures/Emoji');
 const ReactionEmoji = require('../structures/ReactionEmoji');
+const Role = require('../structures/Role');
 
 /**
  * The DataResolver identifies different objects and tries to resolve a specific piece of information from them, e.g.
@@ -101,6 +102,27 @@ class ClientDataResolver {
     return guild.members.get(user.id) || null;
   }
 
+  /**
+   * Data that can be resolved to a Role object. This can be:
+   * * A Role
+   * * A Snowflake
+   * @typedef {Role|Snowflake} RoleResolvable
+   */
+
+  /**
+    * Resolves a RoleResolvable to a Role object.
+    * @param {GuildResolvable} guild The guild that this role is part of
+    * @param {RoleResolvable} role The role resolvable to resolve
+    * @returns {?Role}
+    */
+  resolveRole(guild, role) {
+    if (role instanceof Role) return role;
+    guild = this.resolveGuild(guild);
+    if (!guild) return null;
+    if (typeof role === 'string') return guild.roles.get(role);
+    return null;
+  }
+
   /**
    * Data that can be resolved to give a Channel object. This can be:
    * * A Channel object

src/client/rest/RESTMethods.js

@@ -253,7 +253,30 @@ class RESTMethods {
   }
 
   createChannel(guild, channelName, channelType, overwrites, reason) {
-    if (overwrites instanceof Collection) overwrites = overwrites.array();
+    if (overwrites instanceof Collection || overwrites instanceof Array) {
+      overwrites = overwrites.map(overwrite => {
+        let allow = overwrite.allow || overwrite._allowed;
+        let deny = overwrite.deny || overwrite._denied;
+        if (allow instanceof Array) allow = Permissions.resolve(allow);
+        if (deny instanceof Array) deny = Permissions.resolve(deny);
+
+        const role = this.client.resolver.resolveRole(this, overwrite.id);
+        if (role) {
+          overwrite.id = role.id;
+          overwrite.type = 'role';
+        } else {
+          overwrite.id = this.client.resolver.resolveUserID(overwrite.id);
+          overwrite.type = 'member';
+        }
+
+        return {
+          allow,
+          deny,
+          type: overwrite.type,
+          id: overwrite.id,
+        };
+      });
+    }
     return this.rest.makeRequest('post', Endpoints.Guild(guild).channels, true, {
       name: channelName,
       type: Constants.ChannelTypes[channelType.toUpperCase()],