[ysm] handle linebreak followed by an immediate root-level comment

src/Util/YamlSourceManipulator.php

@@ -915,6 +915,12 @@ private function advanceCurrentPosition(int $newPosition): void
             return;
         }
 
+        if (str_starts_with($advancedContent, "\n#") || str_starts_with($advancedContent, "\r\n#")) {
+            $this->log('A linebreak followed by a root-level comment, no indent changes');
+
+            return;
+        }
+
         if (str_contains($advancedContent, "\n")) {
             $lines = explode("\n", $advancedContent);
             if (!empty($lines)) {

tests/Util/YamlSourceManipulatorTest.php

@@ -48,7 +48,7 @@ public function testSetData(string $startingSource, array $newData, string $expe
         $this->assertSame($expectedSource, $actualContents);
     }
 
-    private function getYamlDataTests()
+    private function getYamlDataTests(): \Generator
     {
         $finder = new Finder();
         $finder->in(__DIR__.'/yaml_fixtures')
@@ -82,14 +82,14 @@ private function getYamlDataTests()
          */
     }
 
-    public function getYamlDataTestsUnixSlashes()
+    public function getYamlDataTestsUnixSlashes(): \Generator
     {
         foreach ($this->getYamlDataTests() as $key => $data) {
             yield 'unix_'.$key => $data;
         }
     }
 
-    public function getYamlDataTestsWindowsSlashes()
+    public function getYamlDataTestsWindowsSlashes(): \Generator
     {
         foreach ($this->getYamlDataTests() as $key => $data) {
             $data['source'] = str_replace("\n", "\r\n", $data['source']);

tests/Util/yaml_fixtures/new_line_with_root_level_comment.test

@@ -0,0 +1,13 @@
+security:
+  firewalls:
+#  main:
+===
+$data['security'] = [
+    'firewalls' => 'a firewall',
+    'providers' => 'a provider'
+];
+===
+security:
+  firewalls: 'a firewall'
+  providers: 'a provider'
+#  main: