Do not mask the render error with "Parent has not been set"

src/Attribute/Base.php

@@ -626,6 +626,30 @@ public function getDefaultRenderSettings()
         return new Simple(['template' => 'mm_attr_' . ($this->get('type') ?? '')]);
     }
 
+    /**
+     * Build the render setting to retry with when rendering with the passed setting has failed.
+     *
+     * The parent is only carried over when the passed setting has one - render settings created on the fly (see
+     * getDefaultRenderSettings()) do not have a parent and must not let the fallback fail with
+     * "Parent has not been set", which would mask the problem that made the rendering fail in the first place.
+     *
+     * @param ISimpleRenderSetting $objSettings The render setting that failed.
+     *
+     * @return ISimpleRenderSetting
+     */
+    protected function getFallbackRenderSetting($objSettings)
+    {
+        $objSettingsFallback = $this->getDefaultRenderSettings();
+
+        try {
+            $parent = $objSettings->getParent();
+        } catch (\RuntimeException) {
+            return $objSettingsFallback;
+        }
+
+        return $objSettingsFallback->setParent($parent);
+    }
+
     /**
      * {@inheritdoc}
      */
@@ -646,17 +670,21 @@ public function parseValue($arrRowData, $strOutputFormat = 'text', $objSettings
 
             // Text rendering is mandatory, try with the current setting,
             // upon exception, try again with the default settings, as the template name might have changed.
-            // if this fails again, we are definitely out of luck and bail the exception.
+            // if this fails again, we are definitely out of luck and bail the original exception.
             try {
                 $arrResult['text'] = $objTemplate->parse('text', true);
-            } catch (\Exception $e) {
-                // FIXME: this throws when no parent has been set - need to catch!
-                $objSettingsFallback = $this->getDefaultRenderSettings()->setParent($objSettings->getParent());
+            } catch (\Exception $exception) {
+                $objSettingsFallback = $this->getFallbackRenderSetting($objSettings);
 
                 $objTemplate = new Template($objSettingsFallback->get('template') ?? '');
                 $this->prepareTemplate($objTemplate, $arrRowData, $objSettingsFallback);
 
-                $arrResult['text'] = $objTemplate->parse('text', true);
+                try {
+                    $arrResult['text'] = $objTemplate->parse('text', true);
+                } catch (\Exception $fallbackException) {
+                    // Do not mask the real problem with the follow-up error of the fallback rendering.
+                    throw $exception;
+                }
             }
         } else {
             // Text rendering is mandatory, therefore render using default render settings.

tests/Attribute/BaseTest.php

@@ -22,6 +22,9 @@
 
 use MetaModels\Attribute\Base;
 use MetaModels\IMetaModel;
+use MetaModels\Render\Setting\ICollection;
+use MetaModels\Render\Setting\ISimple;
+use MetaModels\Render\Setting\Simple as RenderSetting;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -191,4 +194,56 @@ public function testGetFieldDefinition()
         self::assertEquals('some_widget_class', $fieldDefinition['eval']['tl_class']);
         self::assertEquals(true, $fieldDefinition['eval']['readonly']);
     }
+
+    /**
+     * The fallback render setting must not fail for render settings without parent.
+     *
+     * Settings created on the fly (getDefaultRenderSettings()) have no parent - obtaining it would throw and thereby
+     * mask the problem that made the rendering fail in the first place.
+     *
+     * @return void
+     */
+    public function testGetFallbackRenderSettingWithoutParent()
+    {
+        $attribute = $this->getAttribute();
+
+        $fallback = $this->getFallbackRenderSetting($attribute, new RenderSetting([]));
+
+        self::assertInstanceOf(RenderSetting::class, $fallback);
+        self::assertSame('mm_attr_base', $fallback->get('template'));
+    }
+
+    /**
+     * The parent of the failing render setting is carried over to the fallback when there is one.
+     *
+     * @return void
+     */
+    public function testGetFallbackRenderSettingKeepsParent()
+    {
+        $attribute = $this->getAttribute();
+        $parent    = $this->getMockForAbstractClass(ICollection::class);
+
+        $setting = new RenderSetting([]);
+        $setting->setParent($parent);
+
+        $fallback = $this->getFallbackRenderSetting($attribute, $setting);
+
+        self::assertSame($parent, $fallback->getParent());
+    }
+
+    /**
+     * Call the protected getFallbackRenderSetting method on the passed attribute.
+     *
+     * @param Base    $attribute The attribute to call the method on.
+     * @param ISimple $setting   The render setting that failed.
+     *
+     * @return ISimple
+     */
+    private function getFallbackRenderSetting($attribute, $setting)
+    {
+        $method = new \ReflectionMethod($attribute, 'getFallbackRenderSetting');
+        $method->setAccessible(true);
+
+        return $method->invoke($attribute, $setting);
+    }
 }