[8.x] Fix clone() on EloquentBuilder (#36924)

* Support clone() on EloquentBuilder

* Update Builder.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Database/Eloquent/Builder.php

@@ -1608,6 +1608,16 @@ protected static function registerMixin($mixin, $replace)
         }
     }
 
+    /**
+     * Clone the Eloquent query builder.
+     *
+     * @return static
+     */
+    public function clone()
+    {
+        return clone $this;
+    }
+
     /**
      * Force a clone of the underlying query builder when cloning.
      *

tests/Database/DatabaseEloquentBuilderTest.php

@@ -1497,6 +1497,18 @@ public function testWithCastsMethod()
         $builder->withCasts(['foo' => 'bar']);
     }
 
+    public function testClone()
+    {
+        $query = new BaseBuilder(m::mock(ConnectionInterface::class), new Grammar, m::mock(Processor::class));
+        $builder = new Builder($query);
+        $builder->select('*')->from('users');
+        $clone = $builder->clone()->where('email', 'foo');
+
+        $this->assertNotSame($builder, $clone);
+        $this->assertSame('select * from "users"', $builder->toSql());
+        $this->assertSame('select * from "users" where "email" = ?', $clone->toSql());
+    }
+
     protected function mockConnectionForModel($model, $database)
     {
         $grammarClass = 'Illuminate\Database\Query\Grammars\\'.$database.'Grammar';