exit flag to return non-zero exit status on differences

cmd/root.go

@@ -1,6 +1,7 @@
 package cmd
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"runtime/debug"
@@ -27,16 +28,28 @@ func Execute() {
 	}
 }
 
+var exitOnDifference = false
+
 func run(cmd *cobra.Command, args []string) error {
 	diffCtx, err := diff.NewDiffContext(args[0], args[1])
 	if err != nil {
 		return err
 	}
 	diffs := diffCtx.Diffs()
-	fmt.Printf("%s\n", diffs)
+
+	fmt.Fprintf(cmd.OutOrStdout(), "%s", diffs)
+
+	if exitOnDifference && diffs.HasDifference() {
+		return errors.New("yaml files have difference(s)")
+	}
+
 	return nil
 }
 
+func init() {
+	rootCmd.Flags().BoolVarP(&exitOnDifference, "exit", "e", false, "returns non-zero exit status if there is a difference between yaml files")
+}
+
 // buildVersion is set by ldflags
 var buildVersion string
 

diff/yaml.go

@@ -177,6 +177,10 @@ func (d FileDiffs) String() string {
 	return strings.Join(docDiffsStrings, "\n---\n")
 }
 
+func (d FileDiffs) HasDifference() bool {
+	return len(d) > 0
+}
+
 func NewFileDiffs(ln, rn *ast.File) FileDiffs {
 	var docDiffs = make(FileDiffs, max(len(ln.Docs), len(rn.Docs)))
 	for i := 0; i < len(docDiffs); i++ {

diff/yaml_test.go

@@ -27,3 +27,11 @@ func TestDiffContextDiffs(t *testing.T) {
 	docDiffs := fileDiffs[0]
 	assert.Len(t, docDiffs, 5)
 }
+
+func TestFileDiffsHasDifference(t *testing.T) {
+	diffCtx, err := NewDiffContext(dataFile, dataNewFile)
+	assert.NoError(t, err)
+
+	fileDiffs := diffCtx.Diffs()
+	assert.True(t, fileDiffs.HasDifference())
+}