fix: sticky posts in tags are not pinned to top

composer.json

@@ -53,7 +53,8 @@
             },
             "optional-dependencies": [
                 "fof/byobu",
-                "fof/follow-tags"
+                "fof/follow-tags",
+                "flarum/sticky"
             ]
         },
         "flagrow": {
@@ -70,7 +71,8 @@
         "fof/byobu": "*",
         "fof/follow-tags": "*",
         "flarum/testing": "^1.0.0",
-        "flarum/phpstan": "*"
+        "flarum/phpstan": "*",
+        "flarum/sticky": "*"
     },
     "autoload-dev": {
         "psr-4": {

extend.php

@@ -46,6 +46,9 @@
         ->patch('/fof/discussion-language/{id}', 'fof.discussion-language.update', Api\Controllers\UpdateLanguageController::class)
         ->delete('/fof/discussion-language/{id}', 'fof.discussion-language.delete', Api\Controllers\DeleteLanguageController::class),
 
+    (new Extend\ServiceProvider())
+        ->register(Provider\LanguageFilterProvider::class),
+
     (new Extend\Middleware('forum'))
         ->add(Middleware\AddLanguageFilter::class),
 

src/Middleware/AddLanguageFilter.php

@@ -115,7 +115,7 @@ protected function addQueryParams(ServerRequestInterface $request, array $params
         return $request->withQueryParams($newParams);
     }
 
-    protected function isDiscussionListPath($request)
+    protected function isDiscussionListPath(ServerRequestInterface $request)
     {
         $path = $request->getAttribute('originalUri')->getPath();
 

src/Provider/LanguageFilterProvider.php

@@ -0,0 +1,35 @@
+<?php
+
+/*
+ * This file is part of fof/discussion-language.
+ *
+ * Copyright (c) FriendsOfFlarum.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FoF\DiscussionLanguage\Provider;
+
+use Flarum\Discussion\Filter\DiscussionFilterer;
+use Flarum\Foundation\AbstractServiceProvider;
+use Flarum\Sticky\PinStickiedDiscussionsToTop;
+use FoF\DiscussionLanguage\Sticky\PinStickiedDiscussionsToTop as CustomPinStickiedDiscussionsToTop;
+
+class LanguageFilterProvider extends AbstractServiceProvider
+{
+    public function register()
+    {
+        $this->container->extend('flarum.filter.filter_mutators', function ($mutators) {
+            if (isset($mutators[DiscussionFilterer::class]) && is_array($mutators[DiscussionFilterer::class])) {
+                foreach ($mutators[DiscussionFilterer::class] as $key => $mutator) {
+                    if ($mutator === PinStickiedDiscussionsToTop::class) {
+                        $mutators[DiscussionFilterer::class][$key] = CustomPinStickiedDiscussionsToTop::class;
+                    }
+                }
+            }
+
+            return $mutators;
+        });
+    }
+}

src/Sticky/PinStickiedDiscussionsToTop.php

@@ -0,0 +1,79 @@
+<?php
+
+/*
+ * This file is part of fof/discussion-language.
+ *
+ * Copyright (c) FriendsOfFlarum.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FoF\DiscussionLanguage\Sticky;
+
+use Flarum\Filter\FilterState;
+use Flarum\Query\QueryCriteria;
+use Flarum\Tags\Query\TagFilterGambit;
+
+class PinStickiedDiscussionsToTop
+{
+    public function __invoke(FilterState $filterState, QueryCriteria $criteria)
+    {
+        if ($criteria->sortIsDefault) {
+            $query = $filterState->getQuery();
+
+            // If we are viewing a specific tag, then pin all stickied
+            // discussions to the top no matter what.
+            $filters = $filterState->getActiveFilters();
+
+            if (count($filters) > 0) {
+                // Use array_filter to check if any of the filters is an instance of TagFilterGambit
+                $tagFilterGambits = array_filter($filters, function ($filter) {
+                    return $filter instanceof TagFilterGambit;
+                });
+
+                // Check if there is at least one TagFilterGambit instance
+                if (count($tagFilterGambits) > 0) {
+                    if (!is_array($query->orders)) {
+                        $query->orders = [];
+                    }
+
+                    array_unshift($query->orders, ['column' => 'is_sticky', 'direction' => 'desc']);
+                }
+
+                return;
+            }
+
+            // Otherwise, if we are viewing "all discussions", only pin stickied
+            // discussions to the top if they are unread. To do this in a
+            // performant way we create another query which will select all
+            // stickied discussions, marry them into the main query, and then
+            // reorder the unread ones up to the top.
+            $sticky = clone $query;
+            $sticky->where('is_sticky', true);
+            unset($sticky->orders);
+
+            $query->union($sticky);
+
+            $read = $query->newQuery()
+                ->selectRaw('1')
+                ->from('discussion_user as sticky')
+                ->whereColumn('sticky.discussion_id', 'id')
+                ->where('sticky.user_id', '=', $filterState->getActor()->id)
+                ->whereColumn('sticky.last_read_post_number', '>=', 'last_post_number');
+
+            // Add the bindings manually (rather than as the second
+            // argument in orderByRaw) for now due to a bug in Laravel which
+            // would add the bindings in the wrong order.
+            $query->orderByRaw('is_sticky and not exists ('.$read->toSql().') and last_posted_at > ? desc')
+                ->addBinding(array_merge($read->getBindings(), [$filterState->getActor()->marked_all_as_read_at ?: 0]), 'union');
+
+            $query->unionOrders = array_merge($query->unionOrders, $query->orders);
+            $query->unionLimit = $query->limit;
+            $query->unionOffset = $query->offset;
+
+            $query->limit = $sticky->limit = $query->offset + $query->limit;
+            unset($query->offset, $sticky->offset);
+        }
+    }
+}