Merge pull request #14 from vijtrip2/import-test

Correctly validate the nil check for interfaces.

Author: jaypipes

pkg/compare/nil.go

@@ -13,13 +13,37 @@
 
 package compare
 
+import (
+	"reflect"
+)
+
 // HasNilDifference returns true if the supplied subjects' nilness is
 // different
 func HasNilDifference(a, b interface{}) bool {
-	if a == nil || b == nil {
-		if (a == nil && b != nil) || (a != nil && b == nil) {
+	if isNil(a) || isNil(b) {
+		if (isNil(a) && isNotNil(b)) || (isNil(b) && isNotNil(a)) {
 			return true
 		}
 	}
 	return false
 }
+
+// isNil checks the passed interface argument for Nil value.
+// For interfaces, only 'i==nil' check is not sufficient.
+// https://tour.golang.org/methods/12
+// More details: https://mangatmodi.medium.com/go-check-nil-interface-the-right-way-d142776edef1
+func isNil(i interface{}) bool {
+	if i == nil {
+		return true
+	}
+
+	switch reflect.TypeOf(i).Kind() {
+	case reflect.Ptr, reflect.Map, reflect.Array, reflect.Chan, reflect.Slice:
+		return reflect.ValueOf(i).IsNil()
+	}
+	return false
+}
+
+func isNotNil(i interface{}) bool {
+	return !isNil(i)
+}

pkg/compare/nil_test.go

@@ -0,0 +1,46 @@
+package compare_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/aws-controllers-k8s/runtime/pkg/compare"
+)
+
+func TestNilDifference(t *testing.T) {
+	require := require.New(t)
+
+	sampleString := ""
+	var nullPtr *string
+	nonNullPtr := &sampleString
+	var nullMap map[string]string
+	nonNullMap := make(map[string]string)
+	var nullArray []string
+	nonNullArray := make([]string, 0)
+	var nullChan chan int
+	nonNullChan := make(chan int, 0)
+
+	require.False(compare.HasNilDifference(nil, nil))
+	require.False(compare.HasNilDifference("a", "b"))
+	require.True(compare.HasNilDifference(nil, "b"))
+	require.True(compare.HasNilDifference("a", nil))
+
+	//Pointer
+	require.False(compare.HasNilDifference(nullPtr, nil))
+	require.True(compare.HasNilDifference(nullPtr, nonNullPtr))
+
+	//Map
+	require.False(compare.HasNilDifference(nullMap, nil))
+	require.True(compare.HasNilDifference(nullMap, nonNullMap))
+
+	//Array or Slice
+	require.False(compare.HasNilDifference(nullArray, nil))
+	require.True(compare.HasNilDifference(nullArray, nonNullArray))
+
+	//Chan
+	require.False(compare.HasNilDifference(nullChan, nil))
+	require.True(compare.HasNilDifference(nullChan, nonNullChan))
+
+}
+