js

js plugin

WASM custom_step plugin that runs a user JavaScript snippet in an embedded goja interpreter (pure Go, ES5.1 + much ES6). Use it for recipe glue logic that is awkward in shell: parsing, branching, shaping JSON for downstream steps.

The interpreter is sandboxed — scripts can only touch the narrow host API the plugin injects, gated by plugin.yaml.

Action run

plugin: {
	id:     "js"
	action: "run"
	config: {
		code:       "<javascript>"
		args:       {key: "value"}  // optional, bound to global `args`
		timeout_ms: 30000           // optional, default 30s
	}
}

The script's completion value becomes the step's stdout: a string passes through verbatim, anything else is JSON-encoded (so a script returning JSON.stringify(obj) and one returning obj produce the same output). undefined/null yields empty stdout. Consume it downstream with env_from / loop_from.

Host API exposed to scripts

Dry-run

Without --execute the script is still evaluated (catches syntax/logic errors) but side-effecting host calls are stubbed: host.remote_exec returns an empty changed result and kv.put is a no-op. kv.get still reads so logic can branch.

Build & install

GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared -o plugin.wasm .
mkdir -p ~/.config/honey/plugins/js
cp plugin.yaml plugin.wasm ~/.config/honey/plugins/js/

Enable plugins.enabled: true. See examples/recipe/js_step.cue.

Notes

• The wasm module is large (~19 MB) because it embeds a full JS engine; first instantiation per run is correspondingly slower than a tiny plugin.
• timeout_ms interrupts runaway scripts (e.g. while(true){}).
• Pure logic lives in the jsrun/ sub-package (host-testable); main.go is the thin wasm glue that bridges jsrun.HostAPI to honey host functions.