rules: Add InputFromTextWithOptions for go users

This creates a helper function that creates an `Input` given a module as
a string in a given version of Rego. This is being added for the
rego-playground primarily.

Signed-off-by: Charlie Egan <charlie@styra.com>

pkg/rules/rules.go

@@ -132,6 +132,17 @@ func InputFromText(fileName, text string) (Input, error) {
 	return NewInput(map[string]string{fileName: text}, map[string]*ast.Module{fileName: mod}), nil
 }
 
+// InputFromTextWithOptions creates a new Input from raw Rego text while
+// respecting the provided options.
+func InputFromTextWithOptions(fileName, text string, opts ast.ParserOptions) (Input, error) {
+	mod, err := ast.ParseModuleWithOpts(fileName, text, opts)
+	if err != nil {
+		return Input{}, fmt.Errorf("failed to parse module: %w", err)
+	}
+
+	return NewInput(map[string]string{fileName: text}, map[string]*ast.Module{fileName: mod}), nil
+}
+
 func AllGoRules(conf config.Config) []Rule {
 	return []Rule{
 		NewOpaFmtRule(conf),

pkg/rules/rules_test.go

@@ -0,0 +1,40 @@
+package rules
+
+import (
+	"testing"
+
+	"github.com/open-policy-agent/opa/ast"
+)
+
+func TestInputFromTextWithOptions(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		Module      string
+		RegoVersion ast.RegoVersion
+	}{
+		"regov1": {
+			Module: `package test
+p if { true }`,
+			RegoVersion: ast.RegoV1,
+		},
+		"regov0": {
+			Module: `package test
+p { true }`,
+			RegoVersion: ast.RegoV0,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := InputFromTextWithOptions("p.rego", tc.Module, ast.ParserOptions{
+				RegoVersion: tc.RegoVersion,
+			})
+			if err != nil {
+				t.Errorf("Expected no error, got %v", err)
+			}
+		})
+	}
+}