Add new plugin `converse-carbons`

Fixes a bug whereby carbons weren't being enabled because the listener
for `afterResourceBinding` was registered before `converse.initialize`
was called,(which means it was removed as soon as `cleanup` was called
inside `converse.initialize`).

This shows that event `api.listen` API calls can/should only be called
inside the `initialize` method of a plugin (or at least once plugins
have been initialized).

src/headless/converse-carbons.js

@@ -0,0 +1,48 @@
+/**
+ * @module converse-carbons
+ * @copyright The Converse.js contributors
+ * @license Mozilla Public License (MPLv2)
+ * @description Implements support for XEP-0280 Message Carbons
+ */
+
+import log from '@converse/headless/log';
+import { Strophe } from 'strophe.js/src/strophe';
+import { _converse, api, converse } from "./converse-core";
+
+
+/* Ask the XMPP server to enable Message Carbons
+ * See XEP-0280 https://xmpp.org/extensions/xep-0280.html#enabling
+ */
+function enableCarbons () {
+    if (!api.settings.get("message_carbons") || _converse.session?.get('carbons_enabled')) {
+        return;
+    }
+    const carbons_iq = new Strophe.Builder('iq', {
+        'from': _converse.connection.jid,
+        'id': 'enablecarbons',
+        'type': 'set'
+      })
+      .c('enable', {xmlns: Strophe.NS.CARBONS});
+
+    _converse.connection.addHandler((iq) => {
+        if (iq.querySelectorAll('error').length > 0) {
+            log.warn('An error occurred while trying to enable message carbons.');
+        } else {
+            _converse.session.save({'carbons_enabled': true});
+            log.debug('Message carbons have been enabled.');
+        }
+    }, null, "iq", null, "enablecarbons");
+    _converse.connection.send(carbons_iq);
+}
+
+
+converse.plugins.add('converse-carbons', {
+
+    initialize () {
+        api.settings.extend({
+            message_carbons: true
+        });
+
+        api.listen.on('afterResourceBinding', () => enableCarbons());
+    }
+});

src/headless/converse-core.js

@@ -82,13 +82,14 @@ const CORE_PLUGINS = [
     'converse-bookmarks',
     'converse-bosh',
     'converse-caps',
-    'converse-chatboxes',
+    'converse-carbons',
     'converse-chat',
+    'converse-chatboxes',
     'converse-disco',
     'converse-emoji',
+    'converse-headlines',
     'converse-mam',
     'converse-muc',
-    'converse-headlines',
     'converse-ping',
     'converse-pubsub',
     'converse-roster',
@@ -123,7 +124,6 @@ const DEFAULT_SETTINGS = {
         'gl', 'he', 'hi', 'hu', 'id', 'it', 'ja', 'nb', 'nl', 'mr', 'oc',
         'pl', 'pt', 'pt_BR', 'ro', 'ru', 'tr', 'uk', 'vi', 'zh_CN', 'zh_TW'
     ],
-    message_carbons: true,
     nickname: undefined,
     password: undefined,
     persistent_store: 'localStorage',
@@ -1339,33 +1339,6 @@ async function cleanup () {
 }
 
 
-function enableCarbons () {
-    /* Ask the XMPP server to enable Message Carbons
-     * See XEP-0280 https://xmpp.org/extensions/xep-0280.html#enabling
-     */
-    if (!api.settings.get("message_carbons") || !_converse.session || _converse.session.get('carbons_enabled')) {
-        return;
-    }
-    const carbons_iq = new Strophe.Builder('iq', {
-        'from': _converse.connection.jid,
-        'id': 'enablecarbons',
-        'type': 'set'
-      })
-      .c('enable', {xmlns: Strophe.NS.CARBONS});
-    _converse.connection.addHandler((iq) => {
-        if (iq.querySelectorAll('error').length > 0) {
-            log.warn('An error occurred while trying to enable message carbons.');
-        } else {
-            _converse.session.save({'carbons_enabled': true});
-            log.debug('Message carbons have been enabled.');
-        }
-    }, null, "iq", null, "enablecarbons");
-    _converse.connection.send(carbons_iq);
-}
-
-api.listen.on('afterResourceBinding', () => enableCarbons());
-
-
 function fetchLoginCredentials (wait=0) {
     return new Promise(
         debounce((resolve, reject) => {

src/headless/headless.js

@@ -6,15 +6,16 @@ import "./converse-adhoc";       // XEP-0050 Ad Hoc Commands
 import "./converse-bookmarks";   // XEP-0199 XMPP Ping
 import "./converse-bosh";        // XEP-0206 BOSH
 import "./converse-caps";        // XEP-0115 Entity Capabilities
+import "./converse-carbons";     // XEP-0280 Message Carbons
+import "./converse-chat";        // RFC-6121 Instant messaging
 import "./converse-chatboxes";
-import "./converse-chat";        // Support for one-on-one chats
 import "./converse-disco";       // XEP-0030 Service discovery
+import "./converse-headlines";   // Support for headline messages
 import "./converse-mam";         // XEP-0313 Message Archive Management
 import "./converse-muc";         // XEP-0045 Multi-user chat
-import "./converse-headlines";   // Support for headline messages
 import "./converse-ping";        // XEP-0199 XMPP Ping
 import "./converse-pubsub";      // XEP-0060 Pubsub
-import "./converse-roster";      // Contacts Roster
+import "./converse-roster";      // RFC-6121 Contacts Roster
 import "./converse-rsm";         // XEP-0059 Result Set management
 import "./converse-smacks";      // XEP-0198 Stream Management
 import "./converse-status";      // XEP-0199 XMPP Ping