adds test and hints where code snippets are taken from fluxcd#1515

Signed-off-by: ricardo.bartels@telekom.de <ricardo.bartels@telekom.de>

Author: bb-Ricardo

internal/helm/repository/chart_repository.go

@@ -515,13 +515,15 @@ func jsonOrYamlUnmarshal(b []byte, i interface{}) error {
 // In particular, charts may introduce validations that don't impact repository indexes
 // And repository indexes may be generated by older/non-complient software, which doesn't
 // conform to all validations.
+//
+// this code is taken from https://github.com/helm/helm/blob/v3.15.2/pkg/repo/index.go#L402
 func ignoreSkippableChartValidationError(err error) error {
 	verr, ok := err.(chart.ValidationError)
 	if !ok {
 		return err
 	}
 
-	// https://github.com/helm/helm/issues/12748 (JFrog repository strips alias field)
+	// https://github.com/helm/helm/issues/12748 (JFrog repository strips alias field from index)
 	if strings.HasPrefix(verr.Error(), "validation: more than one dependency with name or alias") {
 		return nil
 	}

internal/helm/repository/chart_repository_test.go

@@ -754,3 +754,52 @@ func verifyLocalIndex(t *testing.T, i *repo.IndexFile) {
 		g.Expect(tt.Keywords).To(ContainElements(expect.Keywords))
 	}
 }
+
+// This code is taken from https://github.com/helm/helm/blob/v3.15.2/pkg/repo/index_test.go#L601
+// and refers to: https://github.com/helm/helm/issues/12748
+func TestIgnoreSkippableChartValidationError(t *testing.T) {
+	type TestCase struct {
+		Input        error
+		ErrorSkipped bool
+	}
+	testCases := map[string]TestCase{
+		"nil": {
+			Input: nil,
+		},
+		"generic_error": {
+			Input: fmt.Errorf("foo"),
+		},
+		"non_skipped_validation_error": {
+			Input: chart.ValidationError("chart.metadata.type must be application or library"),
+		},
+		"skipped_validation_error": {
+			Input:        chart.ValidationErrorf("more than one dependency with name or alias %q", "foo"),
+			ErrorSkipped: true,
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			result := ignoreSkippableChartValidationError(tc.Input)
+
+			if tc.Input == nil {
+				if result != nil {
+					t.Error("expected nil result for nil input")
+				}
+				return
+			}
+
+			if tc.ErrorSkipped {
+				if result != nil {
+					t.Error("expected nil result for skipped error")
+				}
+				return
+			}
+
+			if tc.Input != result {
+				t.Error("expected the result equal to input")
+			}
+
+		})
+	}
+}