facet

facet provides reflection for Rust: it gives types a SHAPE associated const with details on the layout, fields, doc comments, attributes, etc.

It can be used for many things, from (de)serialization to pretty-printing, rich debuggers, CLI parsing, reflection in templating engines, code generation, etc.

See https://facet.rs for details.

Workspace contents

The main facet crate re-exports symbols from:

• facet-core, which defines the main components:
  • The Facet trait and implementations for foreign types (mostly libstd)
  • The Shape struct along with various vtables and the whole Def tree
  • Type-erased pointer helpers like PtrUninit, PtrConst, and Opaque
  • Autoderef specialization trick needed for facet-macros
• facet-macros, which implements the Facet derive attribute as a fast/light proc macro powered by unsynn

For struct manipulation and reflection, we have:

• facet-reflect, allows building values of arbitrary shapes in safe code, respecting invariants. It also allows peeking at existing values.

Internal crates include:

• facet-testhelpers a simple log logger and color-backtrace configured with the lightweight btparse backend

Ecosystem

Various crates live under the https://github.com/facet-rs umbrella, and their repositories are kept somewhat-consistent through facet-dev.

Crates are in various states of progress, buyer beware!

In terms of data formats, we have:

• facet-json: JSON format support
• facet-toml: TOML format support
• facet-yaml: YAML format support
• facet-msgpack: MessagePack deserialization
• facet-asn1: ASN.1 format support
• facet-xdr: XDR format support
• facet-kdl: KDL format support (non-functional so far)

Still adjacent to serialization/deserialization, we have:

• facet-urlencoded: URL-encoded form data deserialization
• facet-args: CLI arguments (a-la clap)

As far as utilities go:

• facet-pretty is able to pretty-print Facet types.
• facet-serialize provides generic iterative serialization facilities
• facet-deserialize provides generic iterative deserialization facilities

And the less developed:

• facet-inspect: Provide utilities to inspect the content of a Facet object.
• facet-diff: Provides diffing capabilities for Facet types.

Extended cinematic universe

Some crates are developed completely independently from the facet org:

• facet-v8 provides an experimental Facet/v8 integration
• facet-openapi (experimental) Generates OpenAPI definitions from types that implement Facet
• facet_generate reflects Facet types into Java, Swift and TypeScript
• multi-array-list provides an experimental MultiArrayList type

Sponsors

Thanks to all individual sponsors:

...along with corporate sponsors:

...without whom this work could not exist.

Special thanks

The facet logo was drawn by Misiasart.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.