feat: more informative error message on xml validation errors

Author: adamzero1

lib/internal/Magento/Framework/Config/Dom.php

@@ -121,15 +121,16 @@ public function __construct(
      * Retrieve array of xml errors
      *
      * @param string $errorFormat
+     * @param \DOMDocument|null $dom
      * @return string[]
      */
-    private static function getXmlErrors($errorFormat)
+    private static function getXmlErrors($errorFormat, $dom = null)
     {
         $errors = [];
         $validationErrors = libxml_get_errors();
         if (count($validationErrors)) {
             foreach ($validationErrors as $error) {
-                $errors[] = self::_renderErrorMessage($error, $errorFormat);
+                $errors[] = self::_renderErrorMessage($error, $errorFormat, $dom);
             }
         } else {
             $errors[] = 'Unknown validation error';
@@ -380,7 +381,7 @@ public static function validateDomDocument(
         try {
             $result = $dom->schemaValidate($schema);
             if (!$result) {
-                $errors = self::getXmlErrors($errorFormat);
+                $errors = self::getXmlErrors($errorFormat, $dom);
             }
         } catch (\Exception $exception) {
             $errors = self::getXmlErrors($errorFormat);
@@ -398,10 +399,11 @@ public static function validateDomDocument(
      *
      * @param \LibXMLError $errorInfo
      * @param string $format
+     * @param \DOMDocument|null $dom
      * @return string
      * @throws \InvalidArgumentException
      */
-    private static function _renderErrorMessage(\LibXMLError $errorInfo, $format)
+    private static function _renderErrorMessage(\LibXMLError $errorInfo, $format, $dom = null)
     {
         $result = $format;
         foreach ($errorInfo as $field => $value) {
@@ -424,6 +426,14 @@ private static function _renderErrorMessage(\LibXMLError $errorInfo, $format)
                 }
             }
         }
+        if ($dom) {
+            $xml = explode(PHP_EOL, $dom->saveXml());
+            $lines = array_slice($xml, max(0, $errorInfo->line - 5), 10, true);
+            $result .= 'The xml was: '.PHP_EOL;
+            foreach ($lines as $lineNumber => $line) {
+                $result .= $lineNumber.':'.$line.PHP_EOL;
+            }
+        }
         return $result;
     }