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/client/actions/Action.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const { PartialTypes } = require('../../util/Constants');
+
 /*
 
 ABOUT ACTIONS
@@ -20,6 +22,27 @@ class GenericAction {
   handle(data) {
     return data;
   }
+
+  getChannel(data) {
+    const id = data.channel_id || data.id;
+    return data.channel || (this.client.options.partials.includes(PartialTypes.CHANNEL) ?
+      this.client.channels.add({
+        id,
+        guild_id: data.guild_id,
+      }) :
+      this.client.channels.get(id));
+  }
+
+  getMessage(data, channel) {
+    const id = data.message_id || data.id;
+    return data.message || (this.client.options.partials.includes(PartialTypes.MESSAGE) ?
+      channel.messages.add({
+        id,
+        channel_id: channel.id,
+        guild_id: data.guild_id || (channel.guild ? channel.guild.id : null),
+      }) :
+      channel.messages.get(id));
+  }
 }
 
 module.exports = GenericAction;