Ignore empty fragments. (#10)

When developing a test document, you might comment out some fragment,
but leave the YAML document separator in place. This should result in
an empty fragment rather than an invalid fragment, since the latter
just generates an annoying and unnecessary error.

Signed-off-by: James Peach <[email protected]>

pkg/doc/fragment.go

@@ -16,6 +16,7 @@ package doc
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 
@@ -38,6 +39,10 @@ const (
 	FragmentTypeObject
 	// FragmentTypeModule indicates this Fragment contains a Rego module.
 	FragmentTypeModule
+	// FragmentTypeEmpty indicates this is an empty fragment.
+	// Empty fragments decode as an empty YAML document and typically
+	// result from the user commenting out a chunk of YAML.
+	FragmentTypeEmpty
 )
 
 var _ error = &InvalidFragmentErr{}
@@ -65,6 +70,8 @@ func (t FragmentType) String() string {
 		return "Rego"
 	case FragmentTypeInvalid:
 		return "invalid"
+	case FragmentTypeEmpty:
+		return "empty"
 	default:
 		return "unknown"
 	}
@@ -118,6 +125,22 @@ func hasKindVersion(u *unstructured.Unstructured) bool {
 	return len(k.Version) > 0 && len(k.Kind) > 0
 }
 
+func decodeEmpty(data []byte) error {
+	buffer := bytes.NewReader(data)
+	decoder := yaml.NewYAMLOrJSONDecoder(buffer, buffer.Len())
+
+	into := map[string]interface{}{}
+	if err := decoder.Decode(&into); err != nil {
+		return err
+	}
+
+	if len(into) == 0 {
+		return nil
+	}
+
+	return errors.New("fragment is not empty YAML")
+}
+
 func decodeYAMLOrJSON(data []byte) (*unstructured.Unstructured, error) {
 	buffer := bytes.NewReader(data)
 	decoder := yaml.NewYAMLOrJSONDecoder(buffer, buffer.Len())
@@ -164,6 +187,14 @@ func (f *Fragment) Decode() (FragmentType, error) {
 			return f.Type, nil
 		}
 
+		// If it decoded as an empty YAML doc, that's OK.
+		// This improves the ergonomics of commenting out YAML
+		// chunks.
+		if err := decodeEmpty(f.Bytes); err == nil {
+			f.Type = FragmentTypeEmpty
+			return f.Type, nil
+		}
+
 		return FragmentTypeInvalid,
 			utils.ChainErrors(
 				&InvalidFragmentErr{Type: FragmentTypeObject},

pkg/doc/fragment_test.go

@@ -20,6 +20,7 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+// nolint(gocognit)
 func TestParseFragment(t *testing.T) {
 	type testcase struct {
 		Data string
@@ -69,6 +70,13 @@ func TestParseFragment(t *testing.T) {
 				if f.Rego() == nil {
 					t.Errorf("nil module for rego fragment")
 				}
+			case FragmentTypeEmpty:
+				if f.Object() != nil {
+					t.Errorf("non-nil object for empty fragment")
+				}
+				if f.Rego() != nil {
+					t.Errorf("non-nil module for empty fragment")
+				}
 			default:
 				t.Errorf("invalid fragment type %d", fragType)
 			}
@@ -128,4 +136,13 @@ metadata:
 		Data: `t { x := 42; y := 41; x > y }`,
 		Want: FragmentTypeModule,
 	})
+
+	run(t, "Empty fragment", testcase{
+		Data: `
+# commented: out
+# yaml: foo
+
+`,
+		Want: FragmentTypeEmpty,
+	})
 }

pkg/test/runner.go

@@ -386,8 +386,8 @@ func Run(testDoc *doc.Document, opts ...RunOpt) error {
 					tc.recorder.Update(checkResults...)
 				})
 
-		case doc.FragmentTypeUnknown:
-			// Ignore unknown fragments.
+		case doc.FragmentTypeUnknown, doc.FragmentTypeEmpty:
+			// Ignore unknown and empty fragments.
 
 		case doc.FragmentTypeInvalid:
 			// XXX(jpeach): We can't get here because