Support more types in encoder custom type zero comparison. (#98)

Fixes #97

Author: kisielk

encoder.go

@@ -40,6 +40,29 @@ func (e *Encoder) SetAliasTag(tag string) {
 	e.cache.tag = tag
 }
 
+func isZero(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Func:
+	case reflect.Map, reflect.Slice:
+		return v.IsNil() || v.Len() == 0
+	case reflect.Array:
+		z := true
+		for i := 0; i < v.Len(); i++ {
+			z = z && isZero(v.Index(i))
+		}
+		return z
+	case reflect.Struct:
+		z := true
+		for i := 0; i < v.NumField(); i++ {
+			z = z && isZero(v.Field(i))
+		}
+		return z
+	}
+	// Compare other types directly:
+	z := reflect.Zero(v.Type())
+	return v.Interface() == z.Interface()
+}
+
 func (e *Encoder) encode(v reflect.Value, dst map[string][]string) error {
 	if v.Kind() == reflect.Ptr {
 		v = v.Elem()
@@ -67,7 +90,7 @@ func (e *Encoder) encode(v reflect.Value, dst map[string][]string) error {
 		// Encode non-slice types and custom implementations immediately.
 		if encFunc != nil {
 			value := encFunc(v.Field(i))
-			if opts.Contains("omitempty") && v.Field(i).Interface() == reflect.Zero(reflect.TypeOf(v.Field(i).Interface())).Interface() {
+			if opts.Contains("omitempty") && isZero(v.Field(i)) {
 				continue
 			}
 

encoder_test.go

@@ -1,6 +1,7 @@
 package schema
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
 )
@@ -330,3 +331,28 @@ func TestEncoderWithOmitempty(t *testing.T) {
 	valNotExists(t, "f08", vals)
 	valsExist(t, "f09", []string{"test"}, vals)
 }
+
+func TestRegisterEncoderCustomArrayType(t *testing.T) {
+	type CustomInt []int
+	type S1 struct {
+		SomeInts CustomInt `schema:",omitempty"`
+	}
+
+	ss := []S1{
+		{},
+		{CustomInt{}},
+		{CustomInt{1, 2, 3}},
+	}
+
+	for s := range ss {
+		vals := map[string][]string{}
+
+		encoder := NewEncoder()
+		encoder.RegisterEncoder(CustomInt{}, func(value reflect.Value) string {
+			return fmt.Sprint(value.Interface())
+		})
+
+		encoder.Encode(s, vals)
+		t.Log(vals)
+	}
+}