XSLT Transformer & UBL Validator

A powerful VS Code extension for XML transformation and UBL 2.1 document validation with comprehensive business rules support.

Features

XSLT Transformation with Auto-Validation

• One-Click Transformation: Click the transform button in the editor title bar
• Easy File Selection: Popup dialogs to select your XML and XSLT files
• Flexible Output: View results in editor or save to file
• XSLT 1.0 & 2.0 Support: Uses bundled Saxon-HE (XSLT 2.0); falls back to system xsltproc when available
• Auto-Validation: When transform output is a UBL document, XSD + business rules validation runs automatically
• XSLT Error Tracing: Validation errors in the output link back to the exact line in your XSLT stylesheet that produces the problematic element (visible as "Related Information" in the Problems panel)
• Missing Element Quick Fix: Quick Fix suggestions on missing-element diagnostics to jump to the relevant XSLT template

UBL 2.1 Document Validation

• XSD Schema Validation: Validates against official OASIS UBL 2.1 schemas for all 65+ document types (Invoice, CreditNote, Order, etc.)
• EN16931 Business Rules: European e-invoicing standard compliance (for Invoice and CreditNote)
• Peppol BIS 3.0 Rules: OpenPEPPOL billing specification validation
• Inline Diagnostics: Errors and warnings appear directly on the problematic lines in VS Code's Problems panel
• Smart XPath Resolution: Precise line number mapping from Schematron validation results
• Element-Level Error Mapping: Validation errors are placed on the specific element in the output, not just the root tag

Usage

XSLT Transformation

1. Click the transform button in the editor title bar
2. Select your input XML file
3. Select your XSLT stylesheet
4. Choose to view result in editor or save to file
5. If the output is a UBL document, validation runs automatically and errors appear in the Problems panel with links back to your XSLT source

Or use Command Palette (Cmd+Shift+P): "XSLT: Transform XML"

UBL Validation

1. Open a UBL 2.1 XML document (Invoice, CreditNote, Order, etc.)
2. Click the validate button in the editor title bar or press Cmd+Shift+V (Mac) / Ctrl+Shift+V (Windows/Linux)
3. View validation results in the Problems panel

Commands:

• UBL: Validate Document - Full validation (XSD + EN16931 + Peppol)
• UBL: Validate XSD Only - Schema validation only
• UBL: Validate Business Rules Only - EN16931 + Peppol rules only

Quick Start

Step 1: Install Java (the only prerequisite)

macOS:

brew install openjdk

Ubuntu / Debian:

sudo apt update && sudo apt install default-jre -y

Fedora / RHEL:

sudo dnf install java-17-openjdk -y

Windows (PowerShell as Admin):

winget install EclipseAdoptium.Temurin.21.JRE

Or download the installer from adoptium.net.

Verify it works:

java -version

You should see output like openjdk version "17.0.x" or similar. Any version 8+ works.

Step 2: Install the Extension

Search for "UBL Validator" in VS Code Extensions (Cmd+Shift+X / Ctrl+Shift+X) and click Install. That's it — everything else is bundled.

Step 3: Use It

• Transform XML: Cmd+Shift+P > XSLT: Transform XML
• Validate UBL: Open an XML file and press Cmd+Shift+V (Mac) / Ctrl+Shift+V (Windows/Linux)

Requirements

System Dependencies

• VS Code: 1.74.0 or higher
• Java: 8 or higher — see Quick Start above for install commands

The extension will show a warning on startup if Java is not detected.

Optional Tools (used automatically when available)

These are not required — the extension works without them. When present, they're used as faster alternatives:

• xsltproc: For XSLT 1.0 transforms (pre-installed on macOS/Linux)
• xmllint: For XSD validation (pre-installed on macOS/Linux)

Bundled Components

The extension bundles everything else it needs — no extra downloads:

• Saxon-HE 10.9: XSLT 2.0 processor (MPL-2.0 license)
• XSD Validator: Built-in Java XSD validator
• UBL 2.1 XSD schemas (OASIS) - All 65+ document types
• EN16931 validation rules (European Commission, EUPL-1.2)
• Peppol BIS 3.0 rules (OpenPEPPOL, MPL-2.0)

Supported UBL Document Types

The extension validates all UBL 2.1 document types including:

• Invoice, CreditNote, DebitNote
• Order, OrderResponse, OrderChange, OrderCancellation
• DespatchAdvice, ReceiptAdvice
• Catalogue, CatalogueRequest, CataloguePricingUpdate
• Quotation, RequestForQuotation
• ApplicationResponse, Statement, RemittanceAdvice
• And 50+ more...

Examples

Valid UBL Invoice

<?xml version="1.0" encoding="UTF-8"?>
<Invoice xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2">
  <cbc:ID>INV-2025-001</cbc:ID>
  <cbc:IssueDate>2025-02-01</cbc:IssueDate>
  <!-- Full UBL structure -->
</Invoice>

Validation passes with no errors

Validation Results

• Errors appear as red squiggles on the specific line
• Warnings appear as yellow squiggles
• Rule IDs shown in brackets: [BR-01] Invoice must contain supplier name
• Click any issue to jump to the line

Release Notes

1.3.0

• Bundled Saxon-HE 10.9: no need to install Saxon separately
• Bundled Java XSD validator: xmllint is now optional
• xsltproc is now optional: falls back to bundled Saxon for XSLT transforms
• Java is the only required system dependency
• Non-blocking Java availability check on activation with install link

1.2.0

• Auto-validation after XSLT transform: when output is detected as UBL, XSD + EN16931 + Peppol validation runs automatically
• XSLT error tracing: validation errors link back to the exact element-producing line in your XSLT stylesheet
• Element-level error placement: errors appear on the specific UBL element in the output, not the root tag
• Rule ID coverage for 65+ EN16931 and Peppol root-level rules with static element mapping
• Missing element Quick Fix suggestions in the editor
• Cross-platform compatibility fixes (Windows path handling, CRLF line endings)

1.1.0

• Full UBL 2.1 validation support
• XSD schema validation for all 65+ UBL document types
• EN16931 European e-invoicing standard validation
• Peppol BIS 3.0 business rules
• Inline diagnostics with precise line numbers
• Keyboard shortcut: Cmd+Shift+V / Ctrl+Shift+V

1.0.0

• Initial XSLT transformation functionality

Support

If you find this extension useful, consider supporting development on Ko-fi

Contributing

Issues and pull requests welcome at GitHub

License

MIT License - Copyright (c) 2025 Andrei Vasilcin

Bundled validation artifacts have their own licenses:

• UBL 2.1 XSD: OASIS IPR Policy
• EN16931: EUPL-1.2
• Peppol BIS 3.0: MPL-2.0
• Saxon-HE 10.9: MPL-2.0

See validation-artifacts/README.md for details.