example_test.go

// Copyright 2016 The OPA Authors.  All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.

package ast_test

import (
	"fmt"

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

func ExampleCompiler_Compile() {

	// Define an input module that will be compiled.
	exampleModule := `package opa.example

import data.foo
import input.bar

p[x] { foo[x]; not bar[x]; x >= min_x }
min_x = 100 { true }`

	// Parse the input module to obtain the AST representation.
	mod, err := ast.ParseModule("my_module", exampleModule)
	if err != nil {
		fmt.Println("Parse error:", err)
	}

	// Create a new compiler instance and compile the module.
	c := ast.NewCompiler()

	mods := map[string]*ast.Module{
		"my_module": mod,
	}

	if c.Compile(mods); c.Failed() {
		fmt.Println("Compile error:", c.Errors)
	}

	fmt.Println("Expr 1:", c.Modules["my_module"].Rules[0].Body[0])
	fmt.Println("Expr 2:", c.Modules["my_module"].Rules[0].Body[1])
	fmt.Println("Expr 3:", c.Modules["my_module"].Rules[0].Body[2])
	fmt.Println("Expr 4:", c.Modules["my_module"].Rules[0].Body[3])

	// Output:
	//
	// Expr 1: data.foo[x]
	// Expr 2: not input.bar[x]
	// Expr 3: __local0__ = data.opa.example.min_x
	// Expr 4: gte(x, __local0__)
}

func ExampleQueryCompiler_Compile() {

	// Define an input module that will be compiled.
	exampleModule := `package opa.example

import data.foo
import input.bar

p[x] { foo[x]; not bar[x]; x >= min_x }
min_x = 100 { true }`

	// Parse the input module to obtain the AST representation.
	mod, err := ast.ParseModule("my_module", exampleModule)
	if err != nil {
		fmt.Println("Parse error:", err)
	}

	// Create a new compiler instance and compile the module.
	c := ast.NewCompiler()

	mods := map[string]*ast.Module{
		"my_module": mod,
	}

	if c.Compile(mods); c.Failed() {
		fmt.Println("Compile error:", c.Errors)
	}

	// Obtain the QueryCompiler from the compiler instance. Note, we will
	// compile this query within the context of the opa.example package and
	// declare that a query input named "queryinput" must be supplied. The
	// QueryContext will include the input value so.
	qc := c.QueryCompiler().
		WithContext(
			// Note, the ast.MustParse<X> functions are meant for test
			// purposes only. They will panic if an error occurs. Prefer the
			// ast.Parse<X> functions that return meaningful error messages
			// instead.
			ast.NewQueryContext().
				WithPackage(ast.MustParsePackage(`package opa.example`)).
				WithImports(ast.MustParseImports("import input.query_arg")),
		)

	// Parse the input query to obtain the AST representation.
	query, err := ast.ParseBody(`p[x]; x < query_arg`)
	if err != nil {
		fmt.Println("Parse error:", err)
	}

	compiled, err := qc.Compile(query)
	if err != nil {
		fmt.Println("Compile error:", err)
	}

	fmt.Println("Compiled:", compiled)

	// Output:
	//
	// Compiled: data.opa.example.p[x]; __localq0__ = input.query_arg; lt(x, __localq0__)
}