Best way to apply custom filter to discussions/comments list?

Ser5

php flarum info

Flarum core: 1.8.9
PHP version: 8.3.14
MySQL version: 10.3.39-MariaDB-0ubuntu0.20.04.2
Loaded extensions: Core, date, libxml, openssl, pcre, zlib, filter, hash, json, pcntl, random, Reflection, SPL, session, standard, sodium, mysqlnd, PDO, xml, bcmath, calendar, ctype, curl, dom, mbstring, FFI, fileinfo, ftp, gd, gettext, iconv, imagick, intl, exif, msgpack, mysqli, pdo_mysql, Phar, posix, readline, shmop, SimpleXML, sockets, sysvmsg, sysvsem, sysvshm, tokenizer, xmlreader, xmlwriter, xsl, Zend OPcache, xdebug
+----------------------+------------+--------+
| Flarum Extensions    |            |        |
+----------------------+------------+--------+
| ID                   | Version    | Commit |
+----------------------+------------+--------+
| flarum-flags         | v1.8.2     |        |
| flarum-approval      | v1.8.2     |        |
| flarum-tags          | v1.8.3     |        |
| flarum-markdown      | v1.8.1     |        |
| flarum-suspend       | v1.8.4     |        |
| flarum-subscriptions | v1.8.1     |        |
| flarum-sticky        | v1.8.2     |        |
| flarum-statistics    | v1.8.1     |        |
| flarum-mentions      | v1.8.5     |        |
| flarum-lock          | v1.8.2     |        |
| flarum-likes         | v1.8.1     |        |
| flarum-lang-russian  | 1.40.0     |        |
| flarum-emoji         | v1.8.1     |        |
| flarum-bbcode        | v1.8.0     |        |
| askvortsov-rich-text | v2.1.7     |        |
| acme-hello-world     | dev-master |        |
+----------------------+------------+--------+
Base URL: http://forums.ser5lexx.ru/flarum
Installation path: /var/www/forums/htdocs/flarum
Queue driver: sync
Session driver: file
Mail driver: mail
Debug mode: off

For first take I tried to find some event that can be used to alter selection from database. But found only events that allow to handle posts submission, deletion, etc.

Then I found that the data for showing messages list is collected by \Flarum\Api\Controller\ShowDiscussionController::data() method. Tried to tune the dependency injection container inside root extend.php. Here I tried to write my register() method to see if it can initialize default ShowDiscussionController.

<?php
use Flarum\Extend;

use Flarum\Foundation\AbstractServiceProvider;
use Illuminate\Contracts\Container\Container;
use Flarum\Api\Controller\ShowDiscussionController;

class CustomServiceProvider extends AbstractServiceProvider {
    public function register () {
        //var_dump('register start');
        $this->container->resolving(ShowDiscussionController::class, function (Container $container) {
            var_dump('This line is never being reached'); exit();
            return new ShowDiscussionController(
                $container->make(\Flarum\Discussion\DiscussionRepository::class),
                $container->make(\Flarum\Post\PostRepository::class),
                $container->make(\Flarum\Http\SlugManager::class),
            );
        });
        //var_dump('register end'); exit();
    }
}

return [
    (new Extend\ServiceProvider())->register(CustomServiceProvider::class),
];

This way the discussion page breaks, in source code I can see a message like "Something went wrong trying to load full version of the site...", which can mean that something is changed. "register start" and "register end" works normally, but the line with exit() is never reached. Probably this means that $this->container->resolving() call is technically valid, but when the engine tries to access something in the container, it breaks.

Next, I tried to change routes, to change the controller responding to discussion. Found the routed in vendor/flarum/core/src/Forum/routes.php. Saw this line:

$map->get(
    '/d/{id:\d+(?:-[^/]*)?}[/{near:[^/]*}]',
    'discussion',
    $route->toForum(Content\Discussion::class)
);

It doesn't simply directs to a dedicated controller, but calls complex \Flarum\Http\RouteHandlerFactory::toForum() method. I tried to debug it, but quickly drown in container stuff, ton of callbacks, and other smart things.

So, what really is the right way to solve the task?

hf06

Ser5

Code (extend.php):

<?php

use Flarum\Extend;
use Flarum\Api\Controller\ShowDiscussionController;
use Illuminate\Database\Eloquent\Builder;

return [
    // Limit comments on discussion pages
    (new Extend\ApiController(ShowDiscussionController::class))
        ->prepareDataForSerialization(function ($controller, $data, $request) {
            $actor = $request->getAttribute('actor');

            // Apply restriction only for guests
            if ($actor->isGuest()) {
                // Fetch all posts in the discussion and limit them to the first 3
                $posts = $data->posts()->orderBy('created_at')->take(3);

                // Replace the full post relationship with the limited set
                $data->setRelation('posts', $posts->get());
            }
        }),
];

If you'd like to restrict the number of comments visible to guests on discussion pages while allowing logged-in users to see all comments, you can use the following code in your extend.php file.

This code limits the comments loaded on discussion pages to the first 3 for guests. It ensures that only a subset of comments is sent to the API, thus optimizing the page and protecting sensitive content. Logged-in users are not affected by this restriction.

Code Explanation:

Targeting the Correct Controller:
The ShowDiscussionController handles the API requests for discussion pages. By modifying this controller, we ensure that the changes only affect the comments on these pages.

Guest Check:
Using $actor->isGuest(), we apply the restriction only for users who are not logged in.

Limiting the Comments:
The posts() relationship retrieves all comments for a discussion. By chaining orderBy('created_at') and take(3), we limit the query to only the first three comments.

Replacing the Full Comment Set:
The setRelation('posts', ...) method replaces the default full list of comments with the limited subset we just fetched. This ensures that the API response includes only the first 3 comments for guests.

How to Implement:

Add the provided code snippet to your extend.php file in the root of your Flarum installation.

Clear the Flarum cache with the following command:

php flarum cache:clear

Test the implementation by visiting a discussion page as a guest.

Now, only the first 3 comments will be visible to guests on discussion pages. Logged-in users will still see all comments as usual.

This approach is clean, efficient, and does not affect the database or the actual content stored in Flarum.

Note: Since I was in a hurry while writing the code and making this comment, I got help from artificial intelligence, but I tested it in a real forum and the code works without any problems.

flarum

Your question in theSupport tag seems to be missing the php flarum info output.

Providing this information in your initial request:

reduces back and forth asking for this information
can help us identify the root cause even when they're not apparent from your report
will result in more accurate answers to your request
allows us first-hand to identify the issue in case the Base URL is provided

Please consider editing your post and providing this output, see https://docs.flarum.org/troubleshoot for more information.

Thanks for your understanding.

[bot:require-info-command]

Ser5

Tried one more approach, as written in https://docs.flarum.org/extend/search

I supposed this test code will narrow down comments list to IDs 1-3:

<?php
use Flarum\Extend;
use Flarum\Filter\FilterState;
use Flarum\Query\QueryCriteria;
use Flarum\Post\Filter\PostFilterer;

class MyMutator {
    public function __invoke (FilterState $filterState, QueryCriteria $queryCriteria) {
        $filterState->getQuery()->where('posts.id', '<=', 3);
    }
}

return [
    (new Extend\Filter(PostFilterer::class))->addFilterMutator(MyMutator::class),
];

It works not where I expected - it doesn't apply to comments in a discussion, but to messages in a user profile.
Not there: /flarum/d/1-first
But there: /flarum/u/admin

How is that?

clarkwinkelmann

hf06 I believe your code is bypassing Flarum visibility scopes. It will leak posts that are supposed to be deleted, under validation or otherwise made private by extensions.

Ser5

hf06
Many thanks for the answer. May I know what AI you used? I tried to pester ChatGPT and chinese QWQ - from the former I got buggy code, the latter was mumbling weird philosophy.

clarkwinkelmann , hf06
My primary concern with the AI-proposed code is that it throws away the data that core already selected and then reselects another data from scratch - which isn't very good performance-wise.

That's why I initially was searching for some events that could help with altering WHERE of the query. Then tried to inject my own version of ShowDiscussionController into the container - but failed to inject even original ShowDiscussionController. It should be possible - this article https://docs.flarum.org/extend/search has text:

One key advantage of this split is that it allows searching to be implemented via an external service, such as ElasticSearch. For larger communities, this can be significantly more performant and accurate. There isn't a dedicated extender for this yet, so for now, replacing the default Flarum search driver requires overriding the container bindings of Searcher classes. This is a highly advanced use case; if you're interested in doing this, please reach out on our community forums.

I just not very good at Flarum and Laravel code.

Of course I also didn't know about shenanigans with Extend\ApiController::prepareDataForSerialization() - that is a really curious stuff, shedding more light on Flarum abilities.

hf06

clarkwinkelmann Certainly, you're absolutely right. I suspected that the approach he was trying to use almost worked, but he was progressing through the ListPostsController. This is because he mentioned that it worked on the member page but not on the discussion page. That's why I tried to see if I could proceed using the ShowDiscussionController.

In summary, I believe it was a piece of rushed code written with the help of AI. I'm just experimenting to understand Flarum's structure, and I shared the code in case it might be useful to someone.

Of course, I acknowledge that this is an experimental and somewhat amateurish code structure. Thank you for your warning ❤️

hf06

Ser5 I'm using ChatGPT-4. However, I trained it specifically with Flarum's framework, extensions, and documentation. Initially, even for simple tasks, the code it wrote would cause HTTP 500 errors.

I mentioned that I would share the code on a forum, it wrote the entire explanation for my previous comment on its own.

When I encountered HTTP 500 errors at the beginning, I would tell it where it went wrong and provide log files. Over time, it has improved significantly and continues to evolve 🎉

clarkwinkelmann

To go back to the original question, what you probably need is a visibility scoper

The See Past First Post extension might serve as an example clarkwinkelmann/flarum-ext-see-past-first-postblob/master/src/PostVisibilityScope.php

The filter mutator should also work. The main difference is that a filter mutator would only impact the results where the filterer is used (like the discussion list) whereas the visibility scope will apply everywhere (lists, direct access, email, reference through mentions, etc)