Turn the collection into a base collection if mapWithKeys loses models (

#35129)

src/Illuminate/Database/Eloquent/Collection.php

@@ -258,6 +258,23 @@ public function map(callable $callback)
         }) ? $result->toBase() : $result;
     }
 
+    /**
+     * Run an associative map over each of the items.
+     *
+     * The callback should return an associative array with a single key / value pair.
+     *
+     * @param  callable  $callback
+     * @return \Illuminate\Support\Collection|static
+     */
+    public function mapWithKeys(callable $callback)
+    {
+        $result = parent::mapWithKeys($callback);
+
+        return $result->contains(function ($item) {
+            return ! $item instanceof Model;
+        }) ? $result->toBase() : $result;
+    }
+
     /**
      * Reload a fresh model instance from the database for all the entities.
      *

tests/Database/DatabaseEloquentCollectionTest.php

@@ -228,6 +228,35 @@ public function testMappingToNonModelsReturnsABaseCollection()
         $this->assertEquals(BaseCollection::class, get_class($c));
     }
 
+    public function testMapWithKeys()
+    {
+        $one = m::mock(Model::class);
+        $two = m::mock(Model::class);
+
+        $c = new Collection([$one, $two]);
+
+        $key = 0;
+        $cAfterMap = $c->mapWithKeys(function ($item) use (&$key) {
+            return [$key++ => $item];
+        });
+
+        $this->assertEquals($c->all(), $cAfterMap->all());
+        $this->assertInstanceOf(Collection::class, $cAfterMap);
+    }
+
+    public function testMapWithKeysToNonModelsReturnsABaseCollection()
+    {
+        $one = m::mock(Model::class);
+        $two = m::mock(Model::class);
+
+        $key = 0;
+        $c = (new Collection([$one, $two]))->mapWithKeys(function ($item) use (&$key) {
+            return [$key++ => 'not-a-model'];
+        });
+
+        $this->assertEquals(BaseCollection::class, get_class($c));
+    }
+
     public function testCollectionDiffsWithGivenCollection()
     {
         $one = m::mock(Model::class);