[Mentions] URL generated use cached domain instead of current request domain, breaking multi-domain setups

[huoxin233]

Current Behavior

When using multiple domain setup in config.php:
'url' => 'https://' . \Illuminate\Support\Arr::get($_SERVER, 'HTTP_HOST', 'flarum1.local'),
User mentions and post mentions show incorrect domain (e.g. flarum1.local instead of flarum2.local), while other URLs correctly use the current request domain (e.g. avatar links). You can also see that PostPreview uses relative path which I think can be a fix of this issue.

Steps to Reproduce

1. Setup multiple domain in config.php 'url' => 'https://' . \Illuminate\Support\Arr::get($_SERVER, 'HTTP_HOST', 'your.domain'),
2. Access the website using your first domain (e.g. flarum1.local) and make a post that mention a user or post
3. Access the post using another domain that you had setup (e.g. flarum2.local)
4. The link is still showing the previous domain
5. If you clear cache and refresh, then the link will change to the second domain (flarum2.local)

Expected Behavior

URLs generated by Mentions should respect the current request domain context

Screenshots

No response

Environment

• Flarum version: 1.8.10
• Webserver: nginx
• PHP version: 8.2.7
• Mentions extension version: 1.8.5

Output of php flarum info

Flarum core: 1.8.10
PHP version: 8.2.7
MySQL version: 8.0.35
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, gmp, iconv, imap, exif, mysqli, pdo_mysql, Phar, posix, readline, shmop, SimpleXML, soap, sockets, sysvmsg, sysvsem, sysvshm, tokenizer, xmlreader, xmlrpc, xmlwriter, xsl, zip, Zend OPcache
+--------------------------------+------------+------------------------------------------+
| Flarum Extensions | | |
+--------------------------------+------------+------------------------------------------+
| ID | Version | Commit |
+--------------------------------+------------+------------------------------------------+
| flarum-flags | v1.8.2 | |
| flarum-likes | v1.8.1 | |
| flarum-approval | v1.8.2 | |
| antoinefr-money | v1.3.1 | |
| flarum-tags | v1.8.4 | |
| flarum-subscriptions | v1.8.1 | |
| flarum-suspend | v1.8.4 | |
| ziiven-daily-check-in | v0.3.7 | |
| yannisme-oxotheme | 2.1.8 | |
| ramesh-dada-bbcode-alerts | 6.21 | |
| pipecraft-id-slug | v1.1.0 | |
| ianm-synopsis | 1.3.7 | |
| huoxin-auto-follow-discussion | dev-master | de044890b0d0328bae39407e518e8e1bdca5bab5 |
| glowingblue-null-driver | 1.0.0 | |
| fof-links | 1.3.0 | |
| fof-linguist | 1.1.5 | |
| fof-byobu | 1.4.1 | |
| fof-best-answer | 1.6.4 | |
| flarum-sticky | v1.8.2 | |
| flarum-statistics | v1.8.1 | |
| flarum-nicknames | v1.8.2 | |
| flarum-mentions | v1.8.5 | |
| flarum-markdown | v1.8.1 | |
| flarum-lock | v1.8.2 | |
| flarum-lang-english | v1.8.0 | |
| flarum-lang-chinese-simplified | v1.6.0 | |
| flarum-extension-manager | v1.0.7 | |
| flarum-emoji | v1.8.1 | |
| flarum-bbcode | v1.8.0 | |
| datlechin-usercard-uid | v0.1.1 | |
| clarkwinkelmann-status | 1.0.0 | |
| clarkwinkelmann-circle-groups | 1.0.1 | |
| askvortsov-moderator-warnings | v0.6.3 | |
| afrux-forum-widgets-core | v0.1.7 | |
+--------------------------------+------------+------------------------------------------+

Possible Solution

Use relative path instead of abusolute url for mentions
('/u/admin' instead of 'https://my.domain/u/admin')

Additional Context

No response

[luceos]

I personally don't think that this ought to be in core. If you want to use relative paths to support multi tenancy, you might want to use to listen to the Post Saving event and replace all URL's matching the domain to be relative instead.

[huoxin233]

@luceos But I see that post and user mentions are stored in XML format in the database, I cant do any replacement here

Such replacement can only be done to normal links or image url posted by user

[luceos]

@luceos But I see that post and user mentions are stored in XML format in the database, I cant do any replacement here

Such replacement can only be done to normal links or image url posted by user

That's why you use event observers. While the post is being saved, the content property contains the rendered format. Do a link replacement there from absolute to relative and it should work just fine. I can draft an example if you want, just lmk.

[huoxin233]

That's why you use event observers. While the post is being saved, the content property contains the rendered format. Do a link replacement there from absolute to relative and it should work just fine. I can draft an example if you want, just lmk.

@luceos I tired to listen to Flarum\Post\Event\Saving (not sure if this is the event observer you are refering to), and I dont see any absolute url from mentions
An example will be appreciated

[aral-matrix]

I personally don't think that this ought to be in core. If you want to use relative paths to support multi tenancy, you might want to use to listen to the Post Saving event and replace all URL's matching the domain to be relative instead.

Having seen the issue symptoms, I disagree. I don't know the technical details of the implementation, but the workaround you suggest is not a reasonable solution - also because it could break with any update. It would be great if you could still consider to fix this in "core".

[huoxin233]

I personally don't think that this ought to be in core. If you want to use relative paths to support multi tenancy, you might want to use to listen to the Post Saving event and replace all URL's matching the domain to be relative instead.

Having seen the issue symptoms, I disagree. I don't know the technical details of the implementation, but the workaround you suggest is not a reasonable solution - also because it could break with any update. It would be great if you could still consider to fix this in "core".

Created a workaround for this issue: https://github.com/huoxin233/flarum-ext-relative-url
Feel free to try it out

[aral-matrix]

Having seen the issue symptoms, I disagree. I don't know the technical details of the implementation, but the workaround you suggest is not a reasonable solution - also because it could break with any update. It would be great if you could still consider to fix this in "core".

Created a workaround for this issue: https://github.com/huoxin233/flarum-ext-relative-url Feel free to try it out

I am not in a position to try this out, as I am only a user of the Codeberg resources where the issue is occurring - but also, my appeal to @luceos stands - I think that a relative link in a website should be compatible with whatever URL or IP the web site is being loaded via - so if it is loaded from localhost, the relative link can point to a localhost resource, but if it is loaded from myurl.tld, then surely the relative link should not point to localhost.