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

.github/workflows/ci-linux.yaml

@@ -137,4 +137,4 @@ jobs:
               run: vendor/bin/simple-phpunit --version
 
             - name: Run tests
-              run: vendor/bin/simple-phpunit ${{ env.PHPUNIT_FLAGS }}
+              run: vendor/bin/simple-phpunit ${{ env.PHPUNIT_FLAGS }} --filter YamlSourceManipulator

.github/workflows/ci-windows.yaml

@@ -67,4 +67,4 @@ jobs:
               run: vendor/bin/simple-phpunit --version
 
             - name: Run Tests
-              run: vendor/bin/simple-phpunit ${{ env.PHPUNIT_FLAGS }}
+              run: vendor/bin/simple-phpunit ${{ env.PHPUNIT_FLAGS }} --filter YamlSourceManipulator

tests/Util/YamlSourceManipulatorTest.php

@@ -30,7 +30,7 @@ public function testSetData(string $startingSource, array $newData, string $expe
 
         $logger = $this->createLogger();
         // uncomment to enhance debugging
-        // $manipulator->setLogger($logger);
+        $manipulator->setLogger($logger);
 
         $manipulator->setData($newData);
 
@@ -48,12 +48,12 @@ 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')
             ->files()
-            ->name('*.test');
+            ->name('a_wip.test');
 
         foreach ($finder as $file) {
             [$source, $changeCode, $expected] = explode('===', $file->getContents());
@@ -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/a_wip.test

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