valueIsScalar improvements

diff/diff.go

@@ -43,8 +43,8 @@ func Diff(lhs, rhs interface{}, opts ...ConfigOpt) (Differ, error) {
 }
 
 func diff(c config, lhs, rhs interface{}, visited *visited) (Differ, error) {
-	lhsVal := reflect.ValueOf(lhs)
-	rhsVal := reflect.ValueOf(rhs)
+	lhsVal, lhs := indirectValueOf(lhs)
+	rhsVal, rhs := indirectValueOf(rhs)
 
 	if d, ok := nilCheck(lhs, rhs); ok {
 		return d, nil
@@ -56,7 +56,7 @@ func diff(c config, lhs, rhs interface{}, visited *visited) (Differ, error) {
 		return types{lhs, rhs}, ErrCyclic
 	}
 
-	if valuesAreScalar(lhsVal, rhsVal) {
+	if valueIsScalar(lhsVal) && valueIsScalar(rhsVal) {
 		return scalar{lhs, rhs}, nil
 	}
 	if lhsVal.Kind() != rhsVal.Kind() {
@@ -75,15 +75,22 @@ func diff(c config, lhs, rhs interface{}, visited *visited) (Differ, error) {
 	return types{lhs, rhs}, &ErrUnsupported{lhsVal.Type(), rhsVal.Type()}
 }
 
-func valuesAreScalar(lhs, rhs reflect.Value) bool {
-	if lhs.Kind() == reflect.Struct || rhs.Kind() == reflect.Struct {
-		return false
+func indirectValueOf(i interface{}) (reflect.Value, interface{}) {
+	v := reflect.Indirect(reflect.ValueOf(i))
+	if !v.IsValid() || !v.CanInterface() {
+		return reflect.ValueOf(i), i
 	}
-	if lhs.Kind() == reflect.Array || rhs.Kind() == reflect.Array {
+
+	return v, v.Interface()
+}
+
+func valueIsScalar(v reflect.Value) bool {
+	switch v.Kind() {
+	default:
+		return v.Type().Comparable()
+	case reflect.Struct, reflect.Array, reflect.Ptr, reflect.Chan:
 		return false
 	}
-
-	return lhs.Type().Comparable() && rhs.Type().Comparable()
 }
 
 func nilCheck(lhs, rhs interface{}) (Differ, bool) {

diff/diff_test.go

@@ -2,6 +2,7 @@ package diff
 
 import (
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -1128,3 +1129,32 @@ func TestIsSlice(t *testing.T) {
 		t.Error("IsSlice(Diff(map{...}, map{...})) = false, expected true")
 	}
 }
+
+func TestValueIsScalar(t *testing.T) {
+	for _, test := range []struct {
+		In       interface{}
+		Expected bool
+	}{
+		{int(42), true},
+		{int8(23), true},
+		{"foo", true},
+		{true, true},
+		{float32(1.2), true},
+		{complex(5, -3), true},
+
+		{[]byte("foo"), false},
+		{struct{}{}, false},
+		{&struct{}{}, false},
+		{[]int{1, 2, 3}, false},
+		{[3]int{1, 2, 3}, false},
+		{map[string]int{"foo": 22}, false},
+		{func() {}, false},
+		{make(chan struct{}), false},
+	} {
+		v := reflect.ValueOf(test.In)
+		got := valueIsScalar(v)
+		if got != test.Expected {
+			t.Errorf("valueIsScalar(%T) = %v, expected %v", test.In, got, test.Expected)
+		}
+	}
+}