Xantham

The Xantham repository is a collection of .NET and Fable F# libraries and projects that provide a pipeline for encoding TypeScript type information into a JSON schema, and decoding that schema into F# types.

|- src/
    |- Xantham.Common/
    |- Xantham.Fable/
    |- Xantham.Fable.Core/
    |- Xantham.Decoder/
    |- Xantham.Generator/

Xantham Pipeline

The Xantham pipeline is a two phase process of encoding ts information into a json internal representation (IR) via Fable, and then decoding the IR into .NET for use in generators.

// == Encoding Phase ==          == Decoding Phase ==
TypeScript -> Fable -> | IR Json | -> Decoder -> .NET

Common

This project is not built/packaged; the Encoder and Decoder projects include the src/Xantham.Common/Common.Types.fs file directly into their builds instead.

src/Xantham.Common is a mono-file project that provides the communication scheme between the two phases.

Fable

src/Xantham.Fable is the encoding library and/or CLI tool which produces the json IR for consumption by the decoder.

The core functionality is quite generic usage of the TypeScript compiler API, but provides high level interfaces and abstractions for a stack-based iterative approach to traversing the type hierarchies using signals to propagate changes, with the ability to trace type nodes through the pipeline for debugging if required.

The type hierarchy is then encoded using Thoth.Json manual encoders.

The section for Xantham.Fable documents the main API, usage, and development of the library/tool.

Decoder

src/Xantham.Decoder is a .NET library responsible for decoding the JSON schema emitted by Xantham.Fable into strongly-typed F# structures.

It provides the utility layer for convenient generator consumption and handles the conversion from JSON data structures into F# types that can be used by generators.

Generator

The Xantham.Generator project is an example implementation of a consumer of the Xantham.Decoder library. It is suitable for use, and can be extended or changed to fit the needs of your own projects.

src/Xantham.Generator contains the core rendering logic that consumes the decoded schema and generates F# bindings. It provides a foundation for implementing custom generators using the decoded type information from Xantham.Decoder.

Fable.Core

src/Xantham.Fable.Core is a small Fable utility library that provides F# representations of TypeScript type-system idioms that have no direct equivalent in standard F#. All types are erased at runtime — they exist only for the compiler and carry zero overhead in the emitted JavaScript.

It provides utilities for working with keyof type, indexed access types, and heterogeneous property unions that are necessary for complete TypeScript type system support in F#.

The key components in this library are:

• keyof<'T> - TypeScript keyof T
• typekeyof<'T, 'ReturnType> - TypeScript keyof T with value-type retention
• proptypekey<'T, 'ReturnType> and proptypelock<'T> - TypeScript T[keyof T] (union of all property value types)
• PropertyRecord<'T, 'K> - index-signature objects

This library enables more accurate TypeScript to F# translation by handling complex type constructs.