ygot.FormatDiff

ygot/diff.go

@@ -24,6 +24,7 @@ import (
 	"github.com/openconfig/gnmi/errlist"
 	"github.com/openconfig/ygot/internal/yreflect"
 	"github.com/openconfig/ygot/util"
+	"google.golang.org/protobuf/encoding/prototext"
 	"google.golang.org/protobuf/proto"
 
 	gnmipb "github.com/openconfig/gnmi/proto/gnmi"
@@ -488,6 +489,41 @@ func Diff(original, modified GoStruct, opts ...DiffOpt) (*gnmipb.Notification, e
 	}
 }
 
+// FormatDiff formats the output of ygot.Diff as a multiline string. This
+// function is only intended for human consumption and ignores errors. Do not
+// depend on the output being stable. It may change over time across different
+// versions of the program.
+func FormatDiff(n *gnmipb.Notification) string {
+	if n == nil {
+		return "<nil> notification"
+	}
+	var build strings.Builder
+	for _, d := range n.Delete {
+		path, err := PathToString(d)
+		if err != nil {
+			path = prototext.Format(d)
+		}
+		if build.Len() != 0 {
+			build.WriteRune('\n')
+		}
+		build.WriteString(fmt.Sprintf("deleted: %s", path))
+	}
+	for _, u := range n.Update {
+		path, err := PathToString(u.GetPath())
+		if err != nil {
+			path = prototext.Format(u.GetPath())
+		}
+		if build.Len() != 0 {
+			build.WriteRune('\n')
+		}
+		build.WriteString(fmt.Sprintf("new/updated %s: %v", path, u.GetVal()))
+	}
+	if build.Len() == 0 {
+		return "no diff"
+	}
+	return build.String()
+}
+
 // DiffWithAtomic takes an original and modified GoStruct, which must be of the same
 // type and returns a slice of gNMI Notifications that represents the diff
 // between them in a way that can be used to update a local gNMI.Subscribe

ygot/diff_test.go

@@ -1576,6 +1576,9 @@ func TestDiff(t *testing.T) {
 		t.Run(tt.desc+"Diff", func(t *testing.T) {
 			got, err := Diff(tt.inOrig, tt.inMod, tt.inOpts...)
 			testDiffSingleNotif(t, "Diff", got, err)
+			if diffout := FormatDiff(got); diffout == "" {
+				t.Errorf("FormatDiff returned empty")
+			}
 		})
 		t.Run(tt.desc+"DiffWithAtomic", func(t *testing.T) {
 			var got *gnmipb.Notification
@@ -1589,6 +1592,9 @@ func TestDiff(t *testing.T) {
 				t.Fatalf("Got multiple Notifications for DiffWithAtomic: %d, this is not expected.", len(gots))
 			}
 			testDiffSingleNotif(t, "DiffWithAtomic", got, err)
+			if diffout := FormatDiff(got); diffout == "" {
+				t.Errorf("FormatDiff returned empty")
+			}
 		})
 	}
 }