onix-wasm

WASM plugins for builtins.wasm in the onix CppNix fork.

Provides a Nickel evaluator, YAML parser, and INI parser that run inside the Nix evaluator via wasmtime. No IFD, no JSON round-trip.

Plugins

Plugin	Entry points	Description
nickel_plugin.wasm	evalNickel, evalNickelFile, evalNickelFileWith, evalNickelWith	Nickel evaluator with ForeignId passthrough
yaml_plugin.wasm	fromYAML, toYAML	YAML parser/serializer
ini_plugin.wasm	fromINI	INI parser

Nix wrapper

nix/wasm.nix exposes the plugins as regular Nix functions:

let wasm = onix-wasm.lib.${system}; in
{
  config = wasm.evalNickelFile ./config.ncl;
  data = wasm.evalNickelFileWith ./module.ncl { name = "world"; pkg = pkgs.hello; };
  parsed = builtins.head (wasm.fromYAML (builtins.readFile ./config.yaml));
}

ForeignId passthrough

Nix values that aren't simple data types (functions, paths, derivations) pass through the Nickel evaluator as opaque ForeignId handles. They're never serialized -- nickel_to_nix recovers the original Nix value via Value::from_raw(). String contexts are preserved.

Building

nix build  # produces .wasm files in result/

Requires the nickel-wasm-vendor input (vendored nickel-lang-core patched for wasm32).