CLI: Fix normalize YAML block scalar newlines

Author: thim81

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## unreleased
 
+- CLI: Fix normalize YAML block scalar newlines (#202)
+
 ## [1.30.0] - 2026-03-16
 
 - Overlay: add OpenAPI Overlay 1.1.0 support

test/test.js

@@ -16,7 +16,7 @@ const tests = !localTesting
   ? fs.readdirSync(__dirname).filter(file => {
       return fs.statSync(path.join(__dirname, file)).isDirectory() && !file.startsWith('_');
     })
-  : ['yaml-filter-inverse-flags-stripFlags'];
+  : ['yaml-default-newline'];
 
 describe('openapi-format tests', () => {
   let consoleLogSpy, consoleWarnSpy;

test/yaml-default-newline/input.yaml

@@ -0,0 +1,4 @@
+openapi: 3.0.0
+info:
+  description: |2
+     Example

test/yaml-default-newline/options.yaml

@@ -0,0 +1,2 @@
+verbose: true
+output: output.yaml

test/yaml-default-newline/output.yaml

@@ -0,0 +1,4 @@
+openapi: 3.0.0
+info:
+  description: |2
+     Example

utils/file.js

@@ -28,7 +28,7 @@ async function parseString(str, options = {}) {
     try {
       const result = yaml.parseWithPointers(encodedContent, {attachComments: options?.keepComments || false});
       options.yamlComments = result.comments;
-      const obj = result.data;
+      const obj = normalizeYamlBlockScalarNewlines(result.data);
       if (typeof obj === 'object') {
         return obj;
       } else {
@@ -338,6 +338,35 @@ function addQuotesToRefInString(yamlString) {
   return yamlString.replace(/(\$ref:\s*)([^"'\s>]+)/g, '$1"$2"');
 }
 
+/**
+ * Normalize a parser artifact where block scalars with indentation indicators
+ * gain a spurious leading newline during YAML parsing.
+ * This keeps genuine blank first lines intact by only stripping a single
+ * leading newline when the string also has a trailing newline.
+ * @param {*} value - Parsed YAML value.
+ * @returns {*} Normalized value.
+ */
+function normalizeYamlBlockScalarNewlines(value) {
+  if (typeof value === 'string') {
+    if (value.startsWith('\n') && !value.startsWith('\n\n') && value.endsWith('\n')) {
+      return value.slice(1);
+    }
+    return value;
+  }
+
+  if (Array.isArray(value)) {
+    return value.map(item => normalizeYamlBlockScalarNewlines(item));
+  }
+
+  if (value && typeof value === 'object') {
+    for (const key of Object.keys(value)) {
+      value[key] = normalizeYamlBlockScalarNewlines(value[key]);
+    }
+  }
+
+  return value;
+}
+
 /**
  * Analyze the OpenAPI document.
  * @param {object} oaObj - The OpenAPI document as a JSON object.