[7.x] Fix not being able to set component attributes from inside class (#31676)

* Made attributes merge instead of overwrite

* Added test for attribute merging

Author: ryangjchandler

src/Illuminate/View/Component.php

@@ -214,7 +214,7 @@ public function withAttributes(array $attributes)
     {
         $this->attributes = $this->attributes ?: new ComponentAttributeBag;
 
-        $this->attributes->setAttributes($attributes);
+        $this->attributes = $this->attributes->merge($attributes);
 
         return $this;
     }

tests/View/ViewComponentTest.php

@@ -45,6 +45,17 @@ public function testPublicMethodsWithNoArgsAreEagerlyInvokedAndNotCached()
         $component->data();
         $this->assertEquals(3, $component->counter);
     }
+
+    public function testAttributesAreMergedNotOverwritten()
+    {
+        $component = new TestDefaultAttributesComponent;
+
+        $this->assertEquals('text-red-500', $component->attributes->get('class'));
+
+        $component->withAttributes(['class' => 'bg-blue-100']);
+
+        $this->assertEquals('bg-blue-100 text-red-500', $component->attributes->get('class'));
+    }
 }
 
 class TestViewComponent extends Component
@@ -99,3 +110,16 @@ private function privateHello()
         $this->counter++;
     }
 }
+
+class TestDefaultAttributesComponent extends Component
+{
+    public function __construct()
+    {
+        $this->withAttributes(['class' => 'text-red-500']);
+    }
+
+    public function render()
+    {
+        return $this->attributes->get('id');
+    }
+}