Fix an issue where the same mediaCollections could be registered mult…

…iple times. (#3598)

src/InteractsWithMedia.php

@@ -508,7 +508,7 @@ public function addMediaCollection(string $name): MediaCollection
     {
         $mediaCollection = MediaCollection::create($name);
 
-        $this->mediaCollections[] = $mediaCollection;
+        $this->mediaCollections[$name] = $mediaCollection;
 
         return $mediaCollection;
     }

tests/MediaCollections/GetRegisteredMediaCollections.php

@@ -0,0 +1,24 @@
+<?php
+
+use Spatie\MediaLibrary\Tests\TestSupport\TestModels\TestModelWithConversion;
+
+it('calling getRegisteredMediaCollections multiple times should return the same result', function () {
+    $testModel = new class() extends TestModelWithConversion
+    {
+        public function registerMediaCollections(): void
+        {
+            $this->addMediaCollection('images')
+                ->useDisk('secondMediaDisk');
+        }
+    };
+
+    $result = $testModel->getRegisteredMediaCollections();
+    ray($result);
+
+    expect($result)->toHaveCount(1);
+
+    $result = $testModel->getRegisteredMediaCollections();
+    ray($result);
+
+    expect($result)->toHaveCount(1);
+});