v6 API: Missing ESM exports - broken module resolution

[ThePlenkov]

Description

The v6 API source code exists in fast-xml-parser@5.3.1 at src/v6/, but it cannot be imported due to broken ESM module resolution. The internal imports are missing .js file extensions, causing module resolution failures.

Steps to Reproduce

1. Install fast-xml-parser@5.3.1
2. Try to import v6 API as documented:

import XMLParser from 'fast-xml-parser/src/v6/XMLParser.js';
import OutputBuilder from 'fast-xml-parser/src/v6/OutputBuilders/JsObjBuilder.js';

const parser = new XMLParser({
  OutputBuilder: new OutputBuilder()
});

Error

With Node.js:

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/path/to/node_modules/fast-xml-parser/src/v6/valueParsers/trim' 
imported from /path/to/node_modules/fast-xml-parser/src/v6/OutputBuilders/ParserOptionsBuilder.js

With Bun:

SyntaxError: Export named 'JsObjOutputBuilder' not found in module

Root Cause

The v6 source files use imports without .js extensions:

// In src/v6/OutputBuilders/ParserOptionsBuilder.js
import {trim} from '../valueParsers/trim'; // ❌ Missing .js extension

Should be:

import {trim} from '../valueParsers/trim.js'; // ✅ Correct ESM syntax

Impact

• v6 API documentation (getting started guide) references code that doesn't work
• Users cannot use the v6 API features like JsObjOutputBuilder
• Forces users to fall back to v5 API

Workaround

Currently using v5 API with configuration options:

import { XMLParser } from 'fast-xml-parser';
const parser = new XMLParser({
  ignoreAttributes: false,
  attributeNamePrefix: '@_',
  // ... other options
});

Environment

• Package version: fast-xml-parser@5.3.1
• Node.js: v24.10.0
• Bun: v1.3.1
• OS: Linux (WSL2)

Suggestion

Either:

1. Fix ESM imports by adding .js extensions to all internal imports in src/v6/
2. Update package.json to properly export v6 API modules
3. Mark v6 as experimental/unstable in documentation until it's production-ready

---

🤖 AI-assisted via Claude Code
Generated: 2025-11-12T17:01:00Z

[amitguptagwl]

Thanks for highlighting. Just fixed and released.