Refactor `fetchDevices` to make it smaller and simpler to read

src/converse-omemo.js

@@ -950,11 +950,7 @@ converse.plugins.add('converse-omemo', {
                 this.fetchDevices();
             },
 
-            fetchDevices () {
-                if (_.isUndefined(this._devices_promise)) {
-                    this._devices_promise = new Promise(resolve => {
-                        this.devices.fetch({
-                            'success': async collection => {
+            async onDevicesFound (collection) {
                 if (collection.length === 0) {
                     let ids;
                     try {
@@ -963,16 +959,19 @@ converse.plugins.add('converse-omemo', {
                         _converse.log(`Could not fetch devices for ${this.get('jid')}`);
                         _converse.log(e, Strophe.LogLevel.ERROR);
                         this.destroy();
-                                        return resolve(e);
                     }
+                    if (this.get('jid') === _converse.bare_jid) {
                         await this.publishCurrentDevice(ids);
                     }
-                                resolve();
-                            },
-                            'error': e => {
-                                _converse.log(e, Strophe.LogLevel.ERROR);
-                                resolve(e);
                 }
+            },
+
+            fetchDevices () {
+                if (_.isUndefined(this._devices_promise)) {
+                    this._devices_promise = new Promise(resolve => {
+                        this.devices.fetch({
+                            'success': _.flow(c => this.onDevicesFound(c), resolve),
+                            'error': _.flow(_.partial(_converse.log, _, Strophe.LogLevel.ERROR), resolve)
                         });
                     });
                 }
@@ -981,8 +980,7 @@ converse.plugins.add('converse-omemo', {
 
             async publishCurrentDevice (device_ids) {
                 if (this.get('jid') !== _converse.bare_jid) {
-                    // We only publish for ourselves.
-                    return
+                    return // We only publish for ourselves.
                 }
                 await restoreOMEMOSession();
                 let device_id = _converse.omemo_store.get('device_id');