structs: fix nil pointer including, fixes #20

structs.go

@@ -92,7 +92,6 @@ func (s *Struct) Map() map[string]interface{} {
 			// map[string]interface{} too
 			finalVal = Map(val.Interface())
 		} else {
-
 			finalVal = val.Interface()
 		}
 
@@ -400,12 +399,17 @@ func HasZero(s interface{}) bool {
 // IsStruct returns true if the given variable is a struct or a pointer to
 // struct.
 func IsStruct(s interface{}) bool {
-	t := reflect.TypeOf(s)
-	if t.Kind() == reflect.Ptr {
-		t = t.Elem()
+	v := reflect.ValueOf(s)
+	if v.Kind() == reflect.Ptr {
+		v = v.Elem()
 	}
 
-	return t.Kind() == reflect.Struct
+	// uninitialized zero value of a struct
+	if v.Kind() == reflect.Invalid {
+		return false
+	}
+
+	return v.Kind() == reflect.Struct
 }
 
 // Name returns the structs's type name within its package. It returns an

structs_test.go

@@ -773,3 +773,52 @@ func TestName(t *testing.T) {
 
 	Name([]string{})
 }
+
+func TestNestedNilPointer(t *testing.T) {
+	type Collar struct {
+		Engraving string
+	}
+
+	type Dog struct {
+		Name   string
+		Collar *Collar
+	}
+
+	type Person struct {
+		Name string
+		Dog  *Dog
+	}
+
+	person := &Person{
+		Name: "John",
+	}
+
+	personWithDog := &Person{
+		Name: "Ron",
+		Dog: &Dog{
+			Name: "Rover",
+		},
+	}
+
+	personWithDogWithCollar := &Person{
+		Name: "Kon",
+		Dog: &Dog{
+			Name: "Ruffles",
+			Collar: &Collar{
+				Engraving: "If lost, call Kon",
+			},
+		},
+	}
+
+	defer func() {
+		err := recover()
+		if err != nil {
+			fmt.Printf("err %+v\n", err)
+			t.Error("Internal nil pointer should not panic")
+		}
+	}()
+
+	_ = Map(person)                  // Panics
+	_ = Map(personWithDog)           // Panics
+	_ = Map(personWithDogWithCollar) // Doesn't panic
+}