[9.x] Fix inconsistent results of firstOrNew() when using withCasts()

src/Illuminate/Database/Eloquent/Model.php

@@ -493,7 +493,7 @@ public function newInstance($attributes = [], $exists = false)
         // This method just provides a convenient way for us to generate fresh model
         // instances of this current model. It is particularly useful during the
         // hydration of new objects via the Eloquent query builder instances.
-        $model = new static((array) $attributes);
+        $model = new static;
 
         $model->exists = $exists;
 
@@ -505,6 +505,8 @@ public function newInstance($attributes = [], $exists = false)
 
         $model->mergeCasts($this->casts);
 
+        $model->fill((array) $attributes);
+
         return $model;
     }
 

tests/Database/DatabaseEloquentWithCastsTest.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace Illuminate\Tests\Database;
+
+use Illuminate\Database\Capsule\Manager as DB;
+use Illuminate\Database\Eloquent\Model as Eloquent;
+use PHPUnit\Framework\TestCase;
+
+class DatabaseEloquentWithCastsTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $db = new DB;
+
+        $db->addConnection([
+            'driver'   => 'sqlite',
+            'database' => ':memory:',
+        ]);
+
+        $db->bootEloquent();
+        $db->setAsGlobal();
+
+        $this->createSchema();
+    }
+
+    protected function createSchema()
+    {
+        $this->schema()->create('times', function ($table) {
+            $table->increments('id');
+            $table->time('time');
+            $table->timestamps();
+        });
+    }
+
+    public function testWithFirstOrNew()
+    {
+        $time1 = Time::query()->withCasts(['time' => 'string'])
+            ->firstOrNew(['time' => '07:30']);
+
+        Time::query()->insert(['time' => '07:30']);
+
+        $time2 = Time::query()->withCasts(['time' => 'string'])
+            ->firstOrNew(['time' => '07:30']);
+
+        $this->assertSame('07:30', $time1->time);
+        $this->assertSame($time1->time, $time2->time);
+    }
+
+    public function testWithFirstOrCreate()
+    {
+        $time1 = Time::query()->withCasts(['time' => 'string'])
+            ->firstOrCreate(['time' => '07:30']);
+
+        $time2 = Time::query()->withCasts(['time' => 'string'])
+            ->firstOrCreate(['time' => '07:30']);
+
+        $this->assertSame($time1->id, $time2->id);
+    }
+
+    /**
+     * Get a database connection instance.
+     *
+     * @return \Illuminate\Database\Connection
+     */
+    protected function connection()
+    {
+        return Eloquent::getConnectionResolver()->connection();
+    }
+
+    /**
+     * Get a schema builder instance.
+     *
+     * @return \Illuminate\Database\Schema\Builder
+     */
+    protected function schema()
+    {
+        return $this->connection()->getSchemaBuilder();
+    }
+}
+
+class Time extends Eloquent
+{
+    protected $guarded = [];
+
+    protected $casts = [
+        'time' => 'datetime',
+    ];
+}