Check for nil interface correctly

mongox/utils/isnil.go

@@ -0,0 +1,21 @@
+package utils
+
+import (
+	"unsafe"
+)
+
+// IsNil function evaluates the interface value to nil
+func IsNil(i interface{}) bool {
+
+	type iface struct {
+		_   *interface{}
+		ptr unsafe.Pointer
+	}
+
+	unpacked := (*iface)(unsafe.Pointer(&i))
+	if unpacked.ptr == nil {
+		return true
+	}
+
+	return *(*unsafe.Pointer)(unpacked.ptr) == nil
+}

mongox/utils/isnil_test.go

@@ -0,0 +1,32 @@
+package utils
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsNil(t *testing.T) {
+
+	testvalues := []struct {
+		i     interface{}
+		isnil bool
+	}{
+		{nil, true},
+		{(*string)(nil), true},
+		{([]string)(nil), true},
+		{(map[string]string)(nil), true},
+		{(func() bool)(nil), true},
+		{(chan func() bool)(nil), true},
+		{"", true},
+		{0, true},
+		{append(([]string)(nil), ""), false},
+		{[]string{}, false},
+		{1, false},
+		{"1", false},
+	}
+
+	for _, tt := range testvalues {
+		assert.Equal(t, tt.isnil, IsNil(tt.i))
+	}
+}