Notification sent multiple times/for each followed tag

[mfuerni]

Bug Report

Current Behavior
If someone posts to a discussion that is assigned to multiple tags, users that follow multiple of those tags, get the notification multiple times. This even applies if a discussion is assigned to a single tag that has a parent tag, since flarum assigns the parent and the child tag individually to the discussion.

Steps to Reproduce

1. Create a main tag and a sub tag, where the main tag is the parent of the sub tag.
2. Follow/lurk both tags, the main tag and the sub tag.
3. As another user, create a new discussion with the sub tag assigned, or reply to such a discussion.
4. The first user receives two emails with exactly the same content.

Expected Behavior
Per post only a single notification should be sent.

Environment

• Flarum version: 1.8.9
• Extension version: 1.2.7

Flarum core: 1.8.9
PHP version: 8.3.15
MySQL version: 10.5.26-MariaDB-0+deb11u2
Loaded extensions: Core, date, libxml, openssl, pcre, zlib, filter, hash, json, pcntl, random, Reflection, SPL, session, standard, sodium, mysqlnd, PDO, xml, calendar, ctype, curl, dom, mbstring, FFI, fileinfo, ftp, gd, gettext, iconv, imagick, exif, mysqli, pdo_mysql, Phar, posix, readline, shmop, SimpleXML, sockets, sysvmsg, sysvsem, sysvshm, tokenizer, xmlreader, xmlwriter, xsl, zip, Zend OPcache, xdebug
+--------------------------+---------+--------+
| Flarum Extensions        |         |        |
+--------------------------+---------+--------+
| ID                       | Version | Commit |
+--------------------------+---------+--------+
| flarum-flags             | v1.8.2  |        |
| flarum-tags              | v1.8.3  |        |
| flarum-approval          | v1.8.2  |        |
| flarum-mentions          | v1.8.5  |        |
| flarum-subscriptions     | v1.8.1  |        |
| fof-follow-tags          | 1.2.7   |        |
| flarum-suspend           | v1.8.4  |        |
| flarum-sticky            | v1.8.2  |        |
| flarum-statistics        | v1.8.1  |        |
| flarum-markdown          | v1.8.1  |        |
| flarum-lock              | v1.8.2  |        |
| flarum-likes             | v1.8.1  |        |
| flarum-lang-english      | v1.8.0  |        |
| flarum-extension-manager | v1.0.6  |        |
| flarum-emoji             | v1.8.1  |        |
| flarum-bbcode            | v1.8.0  |        |
| askvortsov-categories    | v3.1.0  |        |
+--------------------------+---------+--------+
Base URL: http://localhost:80
Installation path: /mnt/t/flarumTest
Queue driver: sync
Session driver: file
Mail driver: smtp
Debug mode: off

Possible solution(s)
The database queries in src/Jobs/SendNotificationWhen...*.php should add a distinct-filter. Currently, users appear multiple times because of the join with tag_user. I'm not confident with Eloquent, so I leave the coding to others.

Relevant lines:

follow-tags/src/Jobs/SendNotificationWhenDiscussionIsStarted.php

Line 52 in 9b2052f

$notify = User::select('users.*')

follow-tags/src/Jobs/SendNotificationWhenDiscussionIsReTagged.php

Line 59 in 9b2052f

$notify = User::select('users.*')

follow-tags/src/Jobs/SendNotificationWhenReplyIsPosted.php

Line 58 in 9b2052f

$notify = $this->post->discussion->readers()