fix virtual attributes

src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php

@@ -1637,7 +1637,13 @@ protected function mergeAttributesFromClassCasts()
     protected function mergeAttributesFromAttributeCasts()
     {
         foreach ($this->attributeCastCache as $key => $value) {
-            $callback = $this->{Str::camel($key)}()->set ?: function ($value) use ($key) {
+            $attribute = $this->{Str::camel($key)}();
+
+            if ($attribute->get && ! $attribute->set) {
+                continue;
+            }
+
+            $callback = $attribute->set ?: function ($value) use ($key) {
                 $this->attributes[$key] = $value;
             };
 

tests/Integration/Database/DatabaseEloquentModelAttributeCastingTest.php

@@ -177,6 +177,17 @@ public function testSettingRawAttributesClearsTheCastCache()
 
         $this->assertSame('117 Spencer St.', $model->address->lineOne);
     }
+
+    public function testCastsThatOnlyHaveGetterDoNotPeristAnythingToModelOnSave()
+    {
+        $model = new TestEloquentModelWithAttributeCast;
+
+        $model->virtual;
+
+        $model->getAttributes();
+
+        $this->assertTrue(empty($model->getDirty()));
+    }
 }
 
 class TestEloquentModelWithAttributeCast extends Model
@@ -253,6 +264,15 @@ public function password(): Attribute
             return hash('sha256', $value);
         });
     }
+
+    public function virtual(): Attribute
+    {
+        return new Attribute(
+            function () {
+                return collect();
+            }
+        );
+    }
 }
 
 class AttributeCastAddress