XSLT Cannot Extract Namespaced Attributes in v3.4.0

[ThePlenkov]

XSLT Cannot Extract Namespaced Attributes (xslt-processor 3.4.0)

Summary

XSLT transformations cannot extract values from namespaced attributes in XML documents. All standard XPath methods for selecting namespaced attributes return empty strings.

Environment

• Package: xslt-processor
• Version: 3.4.0 (latest as of 2025-11-13)
• Node.js: v24.10.0
• Platform: Linux / WSL2

Minimal Reproducible Example

import xsltProcessor from 'xslt-processor';

const { XmlParser, Xslt } = xsltProcessor;

// Minimal XML with namespaced attribute
const xml = `<?xml version="1.0" encoding="UTF-8"?>
<root xmlns:ns="http://example.com/namespace">
  <element ns:attribute="TestValue" />
</root>`;

// XSLT attempting to extract namespaced attribute
const xslt = `<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:ns="http://example.com/namespace">
  
  <xsl:output method="text"/>
  
  <xsl:template match="/root/element">
    <xsl:text>Method 1 (@ns:attribute): </xsl:text>
    <xsl:value-of select="@ns:attribute"/>
    <xsl:text>&#10;</xsl:text>
    
    <xsl:text>Method 2 (local-name): </xsl:text>
    <xsl:value-of select="@*[local-name()='attribute']"/>
    <xsl:text>&#10;</xsl:text>
    
    <xsl:text>Method 3 (namespace-uri): </xsl:text>
    <xsl:value-of select="@*[local-name()='attribute' and namespace-uri()='http://example.com/namespace']"/>
    <xsl:text>&#10;</xsl:text>
  </xsl:template>
  
</xsl:stylesheet>`;

const xmlDoc = new XmlParser().xmlParse(xml);
const xsltDoc = new XmlParser().xmlParse(xslt);

const processor = new Xslt();
const result = await processor.xsltProcess(xmlDoc, xsltDoc);

console.log(result);
// Output: (completely empty - all three methods return nothing)

Expected Output

Method 1 (@ns:attribute): TestValue
Method 2 (local-name): TestValue
Method 3 (namespace-uri): TestValue

Actual Output

(empty output - all methods return empty strings)

Tested Methods

All standard XPath methods for selecting namespaced attributes fail:

1. Direct namespace prefix: @ns:attribute - ❌ Returns empty
2. local-name(): @*[local-name()='attribute'] - ❌ Returns empty
3. namespace-uri(): @*[local-name()='attribute' and namespace-uri()='...'] - ❌ Returns empty

Real-World Impact

This limitation makes xslt-processor unsuitable for processing XML documents with namespaced attributes, which is common in:

• SAP ADT (ABAP Development Tools) XML responses
• SOAP/XML Web Services
• Atom feeds
• Many enterprise XML formats

Workaround

Use alternative XSLT processors that properly support namespaces:

• Saxon-JS (2.7.0) - Full XSLT 3.0 support, handles namespaces correctly
• Server-side processors - libxslt, Saxon, Xalan

Files to Reproduce

Complete minimal example available at:

• minimal-example.mjs - Runnable test case
• package.json - Dependencies

To reproduce:

npm install
npm test

Related Issues

This appears to be a fundamental limitation in the XPath attribute selection implementation, not a configuration issue. The issue exists in both version 1.x and 3.x (latest).

Question

Is namespace-aware attribute selection intended to be supported in xslt-processor? If not, it would be helpful to document this limitation explicitly to help users choose appropriate alternatives for namespace-heavy XML processing.

[ThePlenkov]

Additional Finding: Output Order Bug with Namespaced Attributes in Named Templates

I've discovered that namespaced attributes can be selected, but there's a critical bug where output is deferred to the end when selecting namespaced attributes within named templates (<xsl:call-template>).

Reproduction

import xsltProcessor from 'xslt-processor';
const { XmlParser, Xslt } = xsltProcessor;

const xml = `<pak:root xmlns:pak="http://test" pak:attr="VALUE"/>`;

const xslt = `<?xml version="1.0"?>
<xsl:stylesheet version="1.0" 
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:pak="http://test">
  <xsl:output method="text"/>
  <xsl:template match="/">
    <xsl:text>A|</xsl:text>
    <xsl:apply-templates select="pak:root"/>
    <xsl:text>|C</xsl:text>
  </xsl:template>
  
  <xsl:template match="pak:root">
    <xsl:text>B|</xsl:text>
    <xsl:call-template name="get-value"/>
    <xsl:text>|D</xsl:text>
  </xsl:template>
  
  <xsl:template name="get-value">
    <xsl:value-of select="@pak:attr"/>
  </xsl:template>
</xsl:stylesheet>`;

const parser = new XmlParser();
const xmlDoc = await parser.xmlParse(xml);
const xsltDoc = await parser.xmlParse(xslt);
const xsltProc = new Xslt();
const result = await xsltProc.xsltProcess(xmlDoc, xsltDoc);

console.log('Expected: A|B|VALUE|D|C');
console.log('Actual:  ', result);

Result

Expected: A|B|VALUE|D|C
Actual:   A|B||D|CVALUE

The VALUE is output at the END instead of in the correct position!

Additional Issues Found

1. ❌ Missing <xsl:strip-space>: Not implemented (throws "not implemented: strip-space")
2. ❌ Output order bug: Namespaced attribute values deferred when selected in named templates
3. ✅ Attributes ARE parsed: They exist in the DOM as child nodes (nodeType: 2)
4. ✅ Simple selection works: Direct <xsl:value-of select="/@ns:attr"/> works in root template

Impact

This makes xslt-processor unsuitable for any real-world XSLT that:

• Uses modular templates (common practice)
• Processes namespace-heavy XML (SAP, SOAP, Atom, etc.)
• Needs to generate structured output formats (like JSON)

Workaround

Use DOM APIs with @xmldom/xmldom instead:

import { DOMParser } from '@xmldom/xmldom';
const doc = new DOMParser().parseFromString(xml, 'text/xml');
const value = doc.documentElement.getAttributeNS('http://test', 'attr');

This is reliable and has no ordering bugs.

[ThePlenkov]

Additional Finding: xml-to-json() Function Also Affected

The namespace attribute extraction issue also impacts the xml-to-json() function, which is available in xslt-processor v3.4.0 but produces empty/whitespace-only output when processing XML with namespaced attributes.

Test Case

import xsltProcessor from 'xslt-processor';
const { XmlParser, Xslt } = xsltProcessor;

// SAP ADT XML with namespaced attributes
const xml = `<?xml version="1.0" encoding="utf-8"?>
<pak:package
        adtcore:responsible="PPLENKOV"
        adtcore:name="$ABAPGIT_EXAMPLES"
        xmlns:pak="http://www.sap.com/adt/packages"
        xmlns:adtcore="http://www.sap.com/adt/core">
    <pak:attributes pak:packageType="development" />
</pak:package>`;

// XSLT using xml-to-json()
const xslt = `<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="text"/>
    <xsl:template match="/">
        <xsl:value-of select="xml-to-json(.)"/>
    </xsl:template>
</xsl:stylesheet>`;

const xmlDoc = new XmlParser().xmlParse(xml);
const xsltDoc = new XmlParser().xmlParse(xslt);
const result = await new Xslt().xsltProcess(xmlDoc, xsltDoc);

console.log(result); // Output: "\n    \n" (just whitespace)

Expected Output

{
  "pak:package": {
    "@adtcore:responsible": "PPLENKOV",
    "@adtcore:name": "$ABAPGIT_EXAMPLES",
    "pak:attributes": {
      "@pak:packageType": "development"
    }
  }
}

Actual Output

"\n    \n"

(Only whitespace/newlines - no actual JSON structure)

Impact

This makes xml-to-json() unusable for:

• Converting namespace-heavy XML to JSON for processing
• SAP ADT responses (all attributes are namespaced)
• SOAP/Web Service responses
• Atom feeds
• Any XML format using namespaced attributes

Root Cause

The xml-to-json() function appears to rely on the same XPath attribute selection mechanism that's broken for namespaced attributes. When it cannot extract namespaced attributes, it produces empty output.

Confirmation

The function exists and is callable (no errors thrown), but the output is effectively useless for namespaced XML:

• ✅ Function is available: xml-to-json() is recognized
• ❌ Output is empty: Returns only whitespace for namespaced XML
• ✅ Works with non-namespaced XML: Simple XML without namespaces produces valid JSON

Test Files

Complete test case available:

• xml-to-json-test.mjs - Demonstrates the issue
• Uses real SAP ADT XML structure

Recommendation

Document that xml-to-json() is not suitable for XML with namespaced attributes until the underlying namespace attribute extraction is fixed.