Add new features to DiffReport and Diff (#48788)

* simplify String for Diff
* add IsAddOperation and IsDeleteOperation to Diff
* add method Paths to DiffReport

pkg/util/cmputil/reporter.go

@@ -78,6 +78,15 @@ func (r DiffReport) String() string {
 	return b.String()
 }
 
+// Paths returns the slice of paths of the current DiffReport
+func (r DiffReport) Paths() []string {
+	var result = make([]string, len(r))
+	for _, diff := range r {
+		result = append(result, diff.Path)
+	}
+	return result
+}
+
 type Diff struct {
 	// Path to the field that has difference separated by period. Array index and key are designated by square brackets.
 	// For example, Annotations[12345].Data.Fields[0].ID
@@ -87,15 +96,34 @@ type Diff struct {
 }
 
 func (d *Diff) String() string {
-	left := d.Left.String()
+	return fmt.Sprintf("%v:\n\t-: %+v\n\t+: %+v\n", d.Path, describeReflectValue(d.Left), describeReflectValue(d.Right))
+}
+
+func describeReflectValue(v reflect.Value) interface{} {
 	// invalid reflect.Value is produced when two collections (slices\maps) are compared and one misses value.
 	// This way go-cmp indicates that an element was added\removed from a list.
-	if !d.Left.IsValid() {
-		left = "<none>"
+	if !v.IsValid() {
+		return "<none>"
 	}
-	right := d.Right.String()
-	if !d.Right.IsValid() {
-		right = "<none>"
-	}
-	return fmt.Sprintf("%v:\n\t-: %+v\n\t+: %+v", d.Path, left, right)
+	return v
+}
+
+// IsAddOperation returns true when
+//  - Left does not have value and Right has
+//  - the kind of Left and Right is either reflect.Slice or reflect.Map and the length of Left is less than length of Right
+// In all other cases it returns false.
+// NOTE: this is applicable to diff of Maps and Slices only
+func (d *Diff) IsAddOperation() bool {
+	return !d.Left.IsValid() && d.Right.IsValid() || (d.Left.Kind() == d.Right.Kind() && // cmp reports adding first element to a nil slice as creation of one and therefore Left is valid and it is nil and right is a new slice
+		(d.Left.Kind() == reflect.Slice || d.Left.Kind() == reflect.Map) && d.Left.Len() < d.Right.Len())
+}
+
+// IsDeleteOperation returns true when
+//  - Right does not have value and Left has
+//  - the kind of Left and Right is either reflect.Slice or reflect.Map and the length of Right is less than length of Left
+// In all other cases it returns false.
+// NOTE: this is applicable to diff of Maps and Slices only
+func (d *Diff) IsDeleteOperation() bool {
+	return d.Left.IsValid() && !d.Right.IsValid() || (d.Left.Kind() == d.Right.Kind() &&
+		(d.Left.Kind() == reflect.Slice || d.Left.Kind() == reflect.Map) && d.Left.Len() > d.Right.Len())
 }