Handle comparisons of boolean values correctly

Add special logic to ensure that the various supported boolean value
representations are treated the same. Closes #334

pkg/dyff/compare_test.go

@@ -88,6 +88,16 @@ some:
 				Expect(result[0]).To(BeSameDiffAs(singleDiff("/some/yaml/structure/name", dyff.MODIFICATION, 1, 2)))
 			})
 
+			It("should return that different representations of true are treated as the same", func() {
+				from := yml("---\nkey: true")
+
+				to := yml("---\nkey: True")
+
+				result, err := compare(from, to)
+				Expect(err).To(BeNil())
+				Expect(result).To(BeNil())
+			})
+
 			It("should return that a float was modified", func() {
 				from := yml(`---
 some:

pkg/dyff/core.go

@@ -212,6 +212,9 @@ func (compare *compare) nonNilSameKindNodes(path ytbx.Path, from *yamlv3.Node, t
 		case "!!null":
 			// Ignore different ways to define a null value
 
+		case "!!bool":
+			diffs, err = compare.boolValues(path, from, to)
+
 		default:
 			if from.Value != to.Value {
 				diffs, err = []Diff{{
@@ -607,6 +610,48 @@ func (compare *compare) nodeValues(path ytbx.Path, from *yamlv3.Node, to *yamlv3
 	return result, nil
 }
 
+func (compare *compare) boolValues(path ytbx.Path, from *yamlv3.Node, to *yamlv3.Node) ([]Diff, error) {
+	boolFrom, err := toBool(from.Value)
+	if err != nil {
+		return nil, err
+	}
+	boolTo, err := toBool(to.Value)
+	if err != nil {
+		return nil, err
+	}
+	result := make([]Diff, 0)
+	if boolFrom != boolTo {
+		result = append(result, Diff{
+			&path,
+			[]Detail{{
+				Kind: MODIFICATION,
+				From: from,
+				To:   to,
+			}},
+		})
+	}
+
+	return result, nil
+}
+
+// this uses the various values mentioned in https://yaml.org/type/bool.html
+var trueValues = [...]string{"y", "Y", "yes", "Yes", "YES", "true", "True", "TRUE", "on", "On", "ON"}
+var falseValues = [...]string{"n", "N", "no", "No", "NO", "false", "False", "FALSE", "off", "Off", "OFF"}
+
+func toBool(input string) (bool, error) {
+	for _, t := range trueValues {
+		if input == t {
+			return true, nil
+		}
+	}
+	for _, f := range falseValues {
+		if input == f {
+			return false, nil
+		}
+	}
+	return false, fmt.Errorf("not a valid boolean value: '%s'", input)
+}
+
 func (compare *compare) findOrderChangesInSimpleList(fromCommon, toCommon []*yamlv3.Node) []Detail {
 	// Try to find order changes ...
 	if len(fromCommon) == len(toCommon) {