Allow using callbacks with load relations extender

src/Api/Controller/AbstractSerializeController.php

@@ -165,15 +165,20 @@ protected function getRelationsToLoad(): array
 
     /**
      * Eager loads the required relationships.
-     *
-     * @param Collection $models
-     * @param array $relations
-     * @return void
      */
-    protected function loadRelations(Collection $models, array $relations): void
+    protected function loadRelations(Collection $models, array $relations, ServerRequestInterface $request = null): void
     {
         $addedRelations = $this->getRelationsToLoad();
 
+        // Filter out callables
+        $callables = [];
+        foreach ($addedRelations as $name => $relation) {
+            if (is_callable($relation)) {
+                $addedRelations[$name] = $name;
+                $callables[$name] = $relation;
+            }
+        }
+
         if (! empty($addedRelations)) {
             usort($addedRelations, function ($a, $b) {
                 return substr_count($a, '.') - substr_count($b, '.');
@@ -194,6 +199,21 @@ protected function loadRelations(Collection $models, array $relations): void
 
         if (! empty($relations)) {
             $relations = array_unique($relations);
+        }
+
+        foreach ($relations as $k => $relation) {
+            if (isset($callables[$relation])) {
+                $load = $callables[$relation];
+
+                $relations[$relation] = function ($query) use ($load, $request) {
+                    $load($query, $request);
+                };
+
+                unset($relations[$k]);
+            }
+        }
+
+        if (! empty($relations)) {
             $models->loadMissing($relations);
         }
     }

src/Api/Controller/ListDiscussionsController.php

@@ -125,7 +125,7 @@ protected function data(ServerRequestInterface $request, Document $document)
 
         $results = $results->getResults();
 
-        $this->loadRelations($results, $include);
+        $this->loadRelations($results, $include, $request);
 
         if ($relations = array_intersect($include, ['firstPost', 'lastPost', 'mostRelevantPost'])) {
             foreach ($results as $discussion) {

src/Api/Controller/ListGroupsController.php

@@ -31,7 +31,7 @@ protected function data(ServerRequestInterface $request, Document $document)
 
         $results = Group::whereVisibleTo($actor)->get();
 
-        $this->loadRelations($results, []);
+        $this->loadRelations($results, [], $request);
 
         return $results;
     }

src/Api/Controller/ListNotificationsController.php

@@ -79,7 +79,7 @@ protected function data(ServerRequestInterface $request, Document $document)
 
         $notifications = $this->notifications->findByUser($actor, $limit + 1, $offset);
 
-        $this->loadRelations($notifications, array_diff($include, ['subject.discussion']));
+        $this->loadRelations($notifications, array_diff($include, ['subject.discussion']), $request);
 
         $notifications = $notifications->all();
 

src/Api/Controller/ListPostsController.php

@@ -108,7 +108,7 @@ protected function data(ServerRequestInterface $request, Document $document)
 
         $results = $results->getResults();
 
-        $this->loadRelations($results, $include);
+        $this->loadRelations($results, $include, $request);
 
         return $results;
     }

src/Api/Controller/ListUsersController.php

@@ -109,7 +109,7 @@ protected function data(ServerRequestInterface $request, Document $document)
 
         $results = $results->getResults();
 
-        $this->loadRelations($results, $include);
+        $this->loadRelations($results, $include, $request);
 
         return $results;
     }

src/Extend/ApiController.php

@@ -13,6 +13,8 @@
 use Flarum\Extension\Extension;
 use Flarum\Foundation\ContainerUtil;
 use Illuminate\Contracts\Container\Container;
+use Illuminate\Database\Query\Builder;
+use Psr\Http\Message\ServerRequestInterface;
 
 class ApiController implements ExtenderInterface
 {
@@ -298,7 +300,7 @@ public function setSort(array $sort, $callback = null): self
      * To force load the relationship, both levels have to be specified,
      * example: ['relation', 'relation.subRelation'].
      *
-     * @param string|string[] $relations
+     * @param string|string[]|array<string, callable(Builder, ServerRequestInterface|null): void> $relations
      * @return self
      */
     public function load($relations): self

tests/integration/extenders/ApiControllerTest.php

@@ -803,6 +803,127 @@ public function custom_second_level_relation_is_not_loaded_when_first_level_is_n
 
         $this->assertTrue($users->pluck('firstLevelRelation')->filter->relationLoaded('secondLevelRelation')->isEmpty());
     }
+
+    /**
+     * @test
+     */
+    public function custom_callable_first_level_relation_is_loaded_if_added()
+    {
+        $users = null;
+
+        $this->extend(
+            (new Extend\Model(User::class))
+                ->hasOne('firstLevelRelation', Post::class, 'user_id'),
+            (new Extend\ApiController(ListUsersController::class))
+                ->load(['firstLevelRelation' => function ($query, $request) {}])
+                ->prepareDataForSerialization(function ($controller, $data) use (&$users) {
+                    $users = $data;
+
+                    return [];
+                })
+        );
+
+        $this->send(
+            $this->request('GET', '/api/users', [
+                'authenticatedAs' => 1,
+            ])
+        );
+
+        $this->assertFalse($users->filter->relationLoaded('firstLevelRelation')->isEmpty());
+    }
+
+    /**
+     * @test
+     */
+    public function custom_callable_second_level_relation_is_loaded_if_added()
+    {
+        $users = null;
+
+        $this->extend(
+            (new Extend\Model(User::class))
+                ->hasOne('firstLevelRelation', Post::class, 'user_id'),
+            (new Extend\Model(Post::class))
+                ->belongsTo('secondLevelRelation', Discussion::class),
+            (new Extend\ApiController(ListUsersController::class))
+                ->load(['firstLevelRelation', 'firstLevelRelation.secondLevelRelation' => function ($query, $request) {}])
+                ->prepareDataForSerialization(function ($controller, $data) use (&$users) {
+                    $users = $data;
+
+                    return [];
+                })
+        );
+
+        $this->send(
+            $this->request('GET', '/api/users', [
+                'authenticatedAs' => 1,
+            ])
+        );
+
+        $this->assertFalse($users->pluck('firstLevelRelation')->filter->relationLoaded('secondLevelRelation')->isEmpty());
+    }
+
+    /**
+     * @test
+     */
+    public function custom_callable_second_level_relation_is_not_loaded_when_first_level_is_not()
+    {
+        $users = null;
+
+        $this->extend(
+            (new Extend\Model(User::class))
+                ->hasOne('firstLevelRelation', Post::class, 'user_id'),
+            (new Extend\Model(Post::class))
+                ->belongsTo('secondLevelRelation', Discussion::class),
+            (new Extend\ApiController(ListUsersController::class))
+                ->load(['firstLevelRelation.secondLevelRelation' => function ($query, $request) {}])
+                ->prepareDataForSerialization(function ($controller, $data) use (&$users) {
+                    $users = $data;
+
+                    return [];
+                })
+        );
+
+        $this->send(
+            $this->request('GET', '/api/users', [
+                'authenticatedAs' => 1,
+            ])
+        );
+
+        $this->assertTrue($users->pluck('firstLevelRelation')->filter->relationLoaded('secondLevelRelation')->isEmpty());
+    }
+
+    /**
+     * @test
+     */
+    public function custom_callable_second_level_relation_is_loaded_when_first_level_is()
+    {
+        $users = null;
+
+        $this->extend(
+            (new Extend\Model(User::class))
+                ->hasOne('firstLevelRelation', Post::class, 'user_id'),
+            (new Extend\Model(Post::class))
+                ->belongsTo('secondLevelRelation', Discussion::class),
+            (new Extend\ApiController(ListUsersController::class))
+                ->load([
+                    'firstLevelRelation' => function ($query, $request) {},
+                    'firstLevelRelation.secondLevelRelation' => function ($query, $request) {}
+                ])
+                ->prepareDataForSerialization(function ($controller, $data) use (&$users) {
+                    $users = $data;
+
+                    return [];
+                })
+        );
+
+        $this->send(
+            $this->request('GET', '/api/users', [
+                'authenticatedAs' => 1,
+            ])
+        );
+
+        $this->assertTrue($users->pluck('firstLevelRelation')->filter->relationLoaded('secondLevelRelation')->isNotEmpty());
+    }
 }
 
 class CustomDiscussionSerializer extends DiscussionSerializer