fix: description is not rendered if doesn't containt markdown headings

fixes #591

Author: RomanHotsiy

src/services/__tests__/models/ApiInfo.test.ts

@@ -0,0 +1,38 @@
+import { ApiInfoModel } from '../../models/ApiInfo';
+import { OpenAPIParser } from '../../OpenAPIParser';
+import { RedocNormalizedOptions } from '../../RedocNormalizedOptions';
+
+const opts = new RedocNormalizedOptions({});
+describe('Models', () => {
+  describe('ResponseModel', () => {
+    let parser: OpenAPIParser;
+
+    beforeEach(() => {
+      parser = new OpenAPIParser({ openapi: '3.0.0' } as any, undefined, opts);
+    });
+
+    test('should correctly populate description field without md headings', () => {
+      parser.spec = {
+        openapi: '3.0.0',
+        info: {
+          description: 'Test description',
+        },
+      } as any;
+
+      const info = new ApiInfoModel(parser);
+      expect(info.description).toEqual('Test description');
+    });
+
+    test('should correctly populate description up to the first md heading', () => {
+      parser.spec = {
+        openapi: '3.0.0',
+        info: {
+          description: 'Test description\nsome text\n## Heading\n test',
+        },
+      } as any;
+
+      const info = new ApiInfoModel(parser);
+      expect(info.description).toEqual('Test description\nsome text\n');
+    });
+  });
+});

src/services/models/ApiInfo.ts

@@ -14,7 +14,10 @@ export class ApiInfoModel implements OpenAPIInfo {
   constructor(private parser: OpenAPIParser) {
     Object.assign(this, parser.spec.info);
     this.description = parser.spec.info.description || '';
-    this.description = this.description.substring(0, this.description.search(/^##?\s+/m));
+    const firstHeadingLinePos = this.description.search(/^##?\s+/m);
+    if (firstHeadingLinePos > -1) {
+      this.description = this.description.substring(0, firstHeadingLinePos);
+    }
   }
 
   get downloadLink(): string | undefined {