[TASK] Do not render `typo3-formengine-updater` if linked field is hidden

TYPO3's TCA type field is rendered in the FormEngine along with a
`<typo3-formengine-updater>` element that listens on changes on the
linked type field.

This is a rare case: if FormEngine is programmatically rendered via an
own controller and the value of the `type` field is hardcoded via
`overrideValues` in the FormEngine compiler, the field itself is not rendered.

However, the `<typo3-formengine-updater>` element is still there,
leaving an "empty" field group.

This patch now checks whether something is available for rendering
before rendering the `<typo3-formengine-updater>` element.

Resolves: #103449
Releases: main
Change-Id: I708b49665dfaa5b836954e40e99cbcb9ed44ec03
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83554


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>

typo3/sysext/backend/Classes/Form/Container/SingleFieldContainer.php

@@ -130,18 +130,19 @@ class SingleFieldContainer extends AbstractContainer
             $options['renderType'] = $parameterArray['fieldConf']['config']['type'];
         }
         $resultArray = $this->nodeFactory->create($options)->render();
-
-        // Render a custom HTML element which will ask the user to save/update the form due to changing the element.
-        // This is used for eg. "type" fields and others configured with "onChange"
-        // (https://docs.typo3.org/m/typo3/reference-tca/main/en-us/Columns/Properties/OnChange.html)
-        $requestFormEngineUpdate =
-            (!empty($this->data['processedTca']['ctrl']['type']) && $fieldName === $typeField)
-            || (isset($parameterArray['fieldConf']['onChange']) && $parameterArray['fieldConf']['onChange'] === 'reload');
-        if ($requestFormEngineUpdate) {
-            $askForUpdate = $backendUser->jsConfirmation(JsConfirmation::TYPE_CHANGE);
-            $requestMode = $askForUpdate ? 'ask' : 'enforce';
-            $fieldSelector = sprintf('[name="%s"]', $parameterArray['itemFormElName']);
-            $resultArray['html'] .= '<typo3-formengine-updater mode="' . htmlspecialchars($requestMode) . '" field="' . htmlspecialchars($fieldSelector) . '"></typo3-formengine-updater>';
+        if ($resultArray['html'] !== '') {
+            // Render a custom HTML element which will ask the user to save/update the form due to changing the element.
+            // This is used for e.g. "type" fields and others configured with "onChange"
+            // (https://docs.typo3.org/m/typo3/reference-tca/main/en-us/Columns/Properties/OnChange.html)
+            $requestFormEngineUpdate =
+                (!empty($this->data['processedTca']['ctrl']['type']) && $fieldName === $typeField)
+                || (isset($parameterArray['fieldConf']['onChange']) && $parameterArray['fieldConf']['onChange'] === 'reload');
+            if ($requestFormEngineUpdate) {
+                $askForUpdate = $backendUser->jsConfirmation(JsConfirmation::TYPE_CHANGE);
+                $requestMode = $askForUpdate ? 'ask' : 'enforce';
+                $fieldSelector = sprintf('[name="%s"]', $parameterArray['itemFormElName']);
+                $resultArray['html'] .= '<typo3-formengine-updater mode="' . htmlspecialchars($requestMode) . '" field="' . htmlspecialchars($fieldSelector) . '"></typo3-formengine-updater>';
+            }
         }
         return $resultArray;
     }