Add TypeScript type definitions for saxonjs-he

[ThePlenkov]

Feature Request: TypeScript Type Definitions

Summary

The saxonjs-he package currently lacks TypeScript type definitions, which causes type errors when using the library in TypeScript projects.

Current Error

Could not find a declaration file for module 'saxonjs-he'. 
'/node_modules/.bun/saxonjs-he@3.0.0-beta2/node_modules/saxonjs-he/SaxonJS3N.js' 
implicitly has an 'any' type.

Try `npm i --save-dev @types/saxonjs-he` if it exists or add a new declaration 
(.d.ts) file containing `declare module 'saxonjs-he';` [ts(7016)]

Use Case

We're building a universal XML ↔ JSON transformer package (xmlt) that relies on Saxon-JS for XSLT transformations. TypeScript type definitions would:

1. Improve developer experience - Enable IDE autocompletion and inline documentation
2. Catch errors at compile time - Detect incorrect API usage before runtime
3. Better integration - Seamless integration with TypeScript projects without type workarounds
4. Self-documenting API - Types serve as living documentation

Example Usage

import SaxonJS from 'saxonjs-he';

// Would love to have proper types here!
const result = await SaxonJS.transform({
  stylesheetInternal: compiledStylesheet,
  sourceText: xmlString,
  destination: 'serialized'
}, 'async');

Proposed Solution

Options for adding TypeScript support:

1. Include .d.ts files in the package - Ship type definitions alongside the JavaScript code
2. Publish @types/saxonjs-he - Create a DefinitelyTyped package
3. Rewrite in TypeScript - Full TypeScript rewrite (most comprehensive but requires more effort)

Workaround

Currently using:

// Temporary workaround - loses all type safety
declare module 'saxonjs-he';

Additional Context

• Package: saxonjs-he@3.0.0-beta2
• Node.js: v24.10.0
• TypeScript: Latest
• Project: Open-source universal XSLT transformer

Saxon-JS is an excellent XSLT processor, and TypeScript definitions would make it even better for modern JavaScript/TypeScript development! 🚀

Would the team be open to adding TypeScript support? Happy to contribute if guidance is provided.

[ndw]

We're investigating what the options are for better TypeScript support. Nothing to report at the moment.

I'm not going to transfer this issue to our tracker, but I encourage you to create future issues there.