Merge branch '13.1'

* 13.1:
  Closes #6590

Author: sebastianbergmann

src/TextUI/Configuration/Xml/Loader.php

@@ -123,6 +123,14 @@ public function load(string $filename): LoadedFromFileConfiguration
 
         $validationResult = (new Validator)->validate($document, $xsdFilename);
 
+        if ($validationResult->hasValidationErrors()) {
+            $this->ensureConfigurationValidatesAgainstAtLeastOneSchema(
+                $document,
+                $configurationFileRealpath,
+                $validationResult,
+            );
+        }
+
         try {
             return new LoadedFromFileConfiguration(
                 $configurationFileRealpath,
@@ -1312,4 +1320,37 @@ private function element(DOMXPath $xpath, string $element): ?DOMElement
 
         return null;
     }
+
+    /**
+     * @throws Exception
+     */
+    private function ensureConfigurationValidatesAgainstAtLeastOneSchema(DOMDocument $document, string $configurationFile, ValidationResult $validationResult): void
+    {
+        if ($document->documentElement->localName === 'phpunit') {
+            return;
+        }
+
+        $schemaFinder = new SchemaFinder;
+        $validator    = new Validator;
+
+        foreach ($schemaFinder->available() as $version) {
+            try {
+                $xsdFilename = $schemaFinder->find($version);
+            } catch (CannotFindSchemaException) {
+                continue;
+            }
+
+            if (!$validator->validate($document, $xsdFilename)->hasValidationErrors()) {
+                return;
+            }
+        }
+
+        throw new Exception(
+            sprintf(
+                'XML configuration file %s does not validate against any supported PHPUnit schema:' . PHP_EOL . '%s',
+                $configurationFile,
+                $validationResult->asString(),
+            ),
+        );
+    }
 }

tests/_files/configuration_invalid_root_element.xml

@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<invalid>
+</invalid>

tests/unit/TextUI/Configuration/Xml/LoaderTest.php

@@ -72,6 +72,15 @@ public function testExceptionIsThrownForNotExistingConfigurationFile(): void
         $this->configuration('not_existing_file.xml');
     }
 
+    public function testExceptionIsThrownForConfigurationFileThatDoesNotValidateAgainstAnySupportedSchema(): void
+    {
+        $this->expectException(Exception::class);
+        $this->expectExceptionMessage('does not validate against any supported PHPUnit schema');
+
+        /* @noinspection UnusedFunctionResultInspection */
+        $this->configuration('configuration_invalid_root_element.xml');
+    }
+
     public function testShouldReadColorsWhenTrueInConfigurationFile(): void
     {
         $phpunit = $this->configuration('configuration.colors.true.xml')->phpunit();