fix:Add required check for customed type binding \n Required tag asso…

…cated with customed type is invalid in previous version. This pr solves this problem by adding required check for customed type binding. What's more, I find that custom type should not only use json tag, because it's useless. This should be pointed out in the document. \n Closes cloudwego#1007

pkg/app/server/binding/binder_test.go

@@ -580,6 +580,74 @@ func TestBind_CustomizedTypeDecodeForPanic(t *testing.T) {
 	})
 }
 
+func TestBind_Required_CustomizedTypeDecode1(t *testing.T) {
+	type Foo struct {
+		F ***CustomizedDecode `query:"a,required"`
+	}
+
+	bindConfig := &BindConfig{}
+	err := bindConfig.RegTypeUnmarshal(reflect.TypeOf(CustomizedDecode{}), func(req *protocol.Request, params param.Params, text string) (reflect.Value, error) {
+		q1 := req.URI().QueryArgs().Peek("a")
+		if len(q1) == 0 {
+			return reflect.Value{}, fmt.Errorf("can be nil")
+		}
+		val := CustomizedDecode{
+			A: string(q1),
+		}
+		return reflect.ValueOf(val), nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	binder := NewDefaultBinder(bindConfig)
+
+	req := newMockRequest().
+		SetRequestURI("http://foobar.com?b=2")
+	result := Foo{}
+	err = binder.Bind(req.Req, &result, nil)
+	if err == nil {
+		t.Fatal("expect an required error, but get nil")
+	}
+}
+
+// TestBind_Required_CustomizedTypeDecode2 is a test case for customized type decoder by json.
+// this case tells us that never only use json tag for customized type. There are two reasons:
+// 1. your customized decoder function will never be called.
+// 2. your customized type must meet json unmarshaler format or you will get an unmarshal error. Since it meet json unmarshaler format, you can use json tag directly.
+func TestBind_Required_CustomizedTypeDecode2(t *testing.T) {
+	type Foo struct {
+		S int              `json:"s"`
+		F CustomizedDecode `json:"f,required"`
+		D string           `json:"d"`
+		Q string           `query:"q"`
+	}
+
+	bindConfig := &BindConfig{}
+	err := bindConfig.RegTypeUnmarshal(reflect.TypeOf(CustomizedDecode{}), func(req *protocol.Request, params param.Params, text string) (reflect.Value, error) {
+		t.Log("CustomizedDecode")
+		q1 := req.URI().QueryArgs().Peek("a")
+		if len(q1) == 0 {
+			return reflect.Value{}, fmt.Errorf("can be nil")
+		}
+		val := CustomizedDecode{
+			A: string(q1),
+		}
+		return reflect.ValueOf(val), nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	binder := NewDefaultBinder(bindConfig)
+
+	req := newMockRequest().
+		SetRequestURI("http://foobar.com?q=dummy").SetJSONContentType().SetBody([]byte(`{"f":54, "d":"d", "s":1}`))
+	result := Foo{}
+	err = binder.Bind(req.Req, &result, nil)
+	if err == nil {
+		t.Fatal("expect an unUnmarshal error, but get nil")
+	}
+}
+
 func TestBind_JSON(t *testing.T) {
 	type Req struct {
 		J1 string    `json:"j1"`

pkg/app/server/binding/internal/decoder/customized_type_decoder.go

@@ -41,6 +41,7 @@
 package decoder
 
 import (
+	"fmt"
 	"reflect"
 
 	"github.com/cloudwego/hertz/pkg/protocol"
@@ -58,6 +59,7 @@ func (d *customizedFieldTextDecoder) Decode(req *protocol.Request, params param.
 	var text string
 	var exist bool
 	var defaultValue string
+	var err error
 	for _, tagInfo := range d.tagInfos {
 		if tagInfo.Skip || tagInfo.Key == jsonTag || tagInfo.Key == fileNameTag {
 			defaultValue = tagInfo.Default
@@ -66,8 +68,15 @@ func (d *customizedFieldTextDecoder) Decode(req *protocol.Request, params param.
 		text, exist = tagInfo.Getter(req, params, tagInfo.Value)
 		defaultValue = tagInfo.Default
 		if exist {
+			err = nil
 			break
 		}
+		if tagInfo.Required {
+			err = fmt.Errorf("'%s' field is a 'required' parameter, but the request does not have this parameter", d.fieldName)
+		}
+	}
+	if err != nil {
+		return err
 	}
 	if !exist {
 		return nil