From AST JSON to Rego

main.go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"os"

	"github.com/open-policy-agent/opa/v1/ast"
	"github.com/open-policy-agent/opa/v1/format"
)

func main() {
	// Read AST JSON from stdin
	b, err := io.ReadAll(os.Stdin)
	if err != nil {
		panic(err)
	}

	// Unmarshal to *Module
	var module ast.Module
	if err = json.Unmarshal(b, &module); err != nil {
		panic(err)
	}

	// Format to Rego
	f := format.MustAstWithOpts(&module, format.Opts{RegoVersion: ast.RegoV1})

	fmt.Println(string(f))
}