Try to validate configuration file against all known schema definitio…

…ns before attempting migration

src/TextUI/Command.php

@@ -840,7 +840,16 @@ private function migrateConfiguration(string $filename): void
     {
         $this->printVersionString();
 
-        if (!(new SchemaDetector)->detect($filename)->detected()) {
+        $result = (new SchemaDetector)->detect($filename);
+
+        if (!$result->detected()) {
+            print $filename . ' does not validate against any know schema.' . PHP_EOL;
+
+            exit(TestRunner::EXCEPTION_EXIT);
+        }
+
+        /** @psalm-suppress MissingThrowsDocblock */
+        if ($result->version() === Version::series()) {
             print $filename . ' does not need to be migrated.' . PHP_EOL;
 
             exit(TestRunner::EXCEPTION_EXIT);

src/Util/Xml/SchemaDetector.php

@@ -26,7 +26,9 @@ public function detect(string $filename): SchemaDetectionResult
             true,
         );
 
-        foreach (['9.2', '8.5'] as $candidate) {
+        $schemaFinder = new SchemaFinder;
+
+        foreach ($schemaFinder->available() as $candidate) {
             $schema = (new SchemaFinder)->find($candidate);
 
             if (!(new Validator)->validate($document, $schema)->hasValidationErrors()) {

tests/end-to-end/migration/_files/unsupported-schema/phpunit.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/0.0/phpunit.xsd"
+>
+    <foo>bar</foo>
+</phpunit>

tests/end-to-end/migration/unsupported-schema.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Configuration migration is not possible when the configuration file does not validate against any known schema
+--FILE--
+<?php declare(strict_types=1);
+$_SERVER['argv'][] = '--do-not-cache-result';
+$_SERVER['argv'][] = '--migrate-configuration';
+
+chdir(sys_get_temp_dir());
+copy(__DIR__ . '/_files/unsupported-schema/phpunit.xml', 'phpunit.xml');
+
+require_once __DIR__ . '/../../bootstrap.php';
+
+PHPUnit\TextUI\Command::main();
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+%sphpunit.xml does not validate against any know schema.
+--CLEAN--
+<?php declare(strict_types=1);
+unlink(sys_get_temp_dir() . '/phpunit.xml');
+unlink(sys_get_temp_dir() . '/phpunit.xml.bak');