BUG#AC-3157: Grouped product with tax throws exception with PHP 8.1

Author: glo80326

app/code/Magento/Tax/Pricing/Render/Adjustment.php

@@ -185,6 +185,6 @@ public function getDataPriceType(): string
     {
         return $this->amountRender->getPriceType() === 'finalPrice'
             ? 'basePrice'
-            : 'base' . ucfirst($this->amountRender->getPriceType());
+            : 'base' . ucfirst($this->amountRender->getPriceType() ?? '');
     }
 }

app/code/Magento/Tax/Test/Unit/Pricing/Render/AdjustmentTest.php

@@ -54,6 +54,11 @@ class AdjustmentTest extends TestCase
      */
     protected $model;
 
+    /**
+     * @var AmountRenderInterface
+     */
+    protected $amountRender;
+
     /**
      * Init mocks and model
      */
@@ -350,4 +355,26 @@ public function testGetHtmlBoth()
 
         $this->model->render($amountRender, $arguments);
     }
+
+    /**
+     * test for method getDataPriceType
+     */
+    public function testGetDataPriceType(): void
+    {
+        $amountRender = $this->getMockBuilder(Amount::class)
+            ->addMethods(['getPriceType'])
+            ->disableOriginalConstructor()
+            ->getMock();
+        $amountRender->expects($this->atLeastOnce())
+            ->method('getPriceType')
+            ->willReturn('finalPrice');
+        $this->model->render($amountRender, []);
+        $this->assertEquals('basePrice', $this->model->getDataPriceType());
+        $amountRender->expects($this->atLeastOnce())
+            ->method('getPriceType')
+            ->willReturn('anythingElse');
+        $this->model->render($amountRender, []);
+        //no exception thrown
+        $this->assertIsString($this->model->getDataPriceType());
+    }
 }