Fix lazy bindToMany relation caching to match eager-loaded collections

src/Phaseolies/Database/Entity/Model.php

@@ -1019,6 +1019,7 @@ public function __get($name)
 
                         case 'bindToMany':
                             $relatedModel = app($this->getLastRelatedModel());
+                            $relatedModelClass = get_class($relatedModel);
                             $pivotColumns = app('db')->getTableColumns($this->getLastPivotTable());
                             $pivotTable = $this->getLastPivotTable();
                             $pivotSelects = array_map(function ($column) use ($pivotTable) {
@@ -1050,7 +1051,11 @@ public function __get($name)
                                 $result->pivot = $pivotObj;
                                 $grouped[$pivot[$this->getLastForeignKey()]][] = $result;
                             }
-                            $this->setRelation($name, $grouped);
+
+                            $this->setRelation(
+                                $name,
+                                new Collection($relatedModelClass, $grouped[$this->getKey()] ?? [])
+                            );
 
                             return $results;
                     }

tests/Model/Query/EntityModelQueryBehavior.php

@@ -2563,12 +2563,15 @@ public function testPostTagRelateMethod()
         $post = MockPost::find(1);
         $post->tags()->relate([1, 2, 3]);
         $this->assertEquals([1, 2, 3], $post->tags->pluck('id')->sort()->values()->toArray());
-        $this->assertCount(1, $post->tags);
+        $this->assertCount(3, $post->tags);
 
         $changes = $post->tags()->relate([1, 2, 4]);
         $this->assertEquals([4], array_keys($changes['attached']));
-        $this->assertEquals([2], array_keys($changes['detached']));
+        $this->assertEquals([3], array_values($changes['detached']));
         $this->assertEquals([], $changes['updated']);
+
+        $post = MockPost::find(1);
+        $this->assertEquals([1, 2, 4], $post->tags->pluck('id')->sort()->values()->toArray());
     }
 
     public function testRepairMethodFetchingRecords()

tests/Model/Query/EntityRelationshipBehavior.php

@@ -228,6 +228,24 @@ public function testBindToManyLazyLoadSingleTag(): void
         $this->assertEquals('Database', $tags[0]->name);
     }
 
+    /**
+     * Re-reading a lazy bindToMany relation should return the cached collection,
+     * not the internal grouped array keyed by the pivot foreign key.
+     */
+    public function testBindToManyLazyLoadCachesCollectionForRepeatedAccess(): void
+    {
+        $post = MockPost::find(1);
+
+        $firstRead = $post->tags;
+        $secondRead = $post->tags;
+
+        $this->assertInstanceOf(Collection::class, $firstRead);
+        $this->assertInstanceOf(Collection::class, $secondRead);
+        $this->assertCount(2, $secondRead);
+        $this->assertEquals('PHP', $secondRead[0]->name);
+        $this->assertEquals(1, $secondRead[0]->pivot->post_id);
+    }
+
     /**
      * Inverse: Tag 1 (PHP) belongs to many Posts.
      */