anchor summary error to field for nested matrix "blocks"

src/controllers/ElementsController.php

@@ -22,6 +22,7 @@
 use craft\events\DefineElementEditorHtmlEvent;
 use craft\events\DraftEvent;
 use craft\fieldlayoutelements\BaseField;
+use craft\fieldlayoutelements\CustomField;
 use craft\fields\Matrix;
 use craft\helpers\ArrayHelper;
 use craft\helpers\Component;
@@ -1046,6 +1047,9 @@ private function _errorSummary(ElementInterface $element): string
  $errorItem .= $error;
  $errorItem .= Html::endTag('li');
  } else {
+ // is the error for multi-nested field (e.g. matrix in a matrix in a blocks mode)
+ $multiNested = substr_count($key, '.') > 1;
+
  // get tab uid for this error
  $tabUid = null;
  $bracketPos = strpos($key, '[');
@@ -1054,7 +1058,21 @@ private function _errorSummary(ElementInterface $element): string
  foreach ($tab->getElements() as $layoutElement) {
  if ($layoutElement instanceof BaseField && $layoutElement->attribute() === $fieldKey) {
  $tabUid = $tab->uid;
- continue 2;
+ if (!$multiNested) {
+ continue 2;
+ }
+ }
+ // if it's a multi-nested error key for matrix in blocks mode
+ // manipulate the key to only reference the matrix field, entry and inner field
+ if ($multiNested && $layoutElement instanceof CustomField) {
+ if (
+ $layoutElement->getField() instanceof Matrix &&
+ $layoutElement->getField()->viewMode === Matrix::VIEW_MODE_BLOCKS
+ ) {
+ $keyParts = explode('.', $key);
+ $key = implode('.', array_splice($keyParts, -2));
+ unset($keyParts);
+ }
  }
  }
  }