Partials (#3070)

* Remove GroupDMChannels

they sparked no joy

* Start partials for message deletion

* MessageUpdate partials

* Add partials as an opt-in client option

* Add fetch() to Message

* Message.author should never be undefined

* Fix channels being the wrong type

* Allow fetching channels

* Refactor and add reaction add partials

* Reaction remove partials

* Check for emoji first

* fix message fetching

janky

* User partials in audit logs

* refactor overwrite code

* guild member partials

* partials as a whitelist

* document GuildMember#fetch

* fix: check whether a structure is a partial, not whether cache is true

* typings: Updated for latest commit (#3075)

* partials: fix messageUpdate behaviour (now "old" message can be partial)

* partials: add warnings and docs

* partials: add partials to index.yml

* partials: tighten "partial" definitions

* partials: fix embed-only messages counting as partials

src/structures/GuildMember.js

@@ -28,7 +28,7 @@ class GuildMember extends Base {
      * The user that this guild member instance represents
      * @type {User}
      */
-    this.user = {};
+    if (data.user) this.user = client.users.add(data.user, true);
 
     /**
      * The timestamp the member joined the guild at
@@ -79,6 +79,14 @@ class GuildMember extends Base {
     return clone;
   }
 
+  /**
+   * Whether this GuildMember is a partial
+   * @type {boolean}
+   */
+  get partial() {
+    return !this.joinedTimestamp;
+  }
+
   /**
    * A collection of roles that are applied to this member, mapped by the role ID
    * @type {GuildMemberRoleStore<Snowflake, Role>}
@@ -355,6 +363,14 @@ class GuildMember extends Base {
     return this.guild.members.ban(this, options);
   }
 
+  /**
+   * Fetches this GuildMember.
+   * @returns {Promise<GuildMember>}
+   */
+  fetch() {
+    return this.guild.members.fetch(this.id, true);
+  }
+
   /**
    * When concatenated with a string, this automatically returns the user's mention instead of the GuildMember object.
    * @returns {string}