refactor(form_mapping.go): mapping multipart request (#1829)

* refactor(form_mapping.go): mapping multipart request

* add checkers for a types to match with the setter interface

* form_mapping.go: rename method name on setter interface, add comments

* fix style of comments

binding/form.go

@@ -4,7 +4,11 @@
 
 package binding
 
-import "net/http"
+import (
+	"mime/multipart"
+	"net/http"
+	"reflect"
+)
 
 const defaultMemory = 32 * 1024 * 1024
 
@@ -53,13 +57,33 @@ func (formMultipartBinding) Bind(req *http.Request, obj interface{}) error {
 	if err := req.ParseMultipartForm(defaultMemory); err != nil {
 		return err
 	}
-	if err := mapForm(obj, req.MultipartForm.Value); err != nil {
+	if err := mappingByPtr(obj, (*multipartRequest)(req), "form"); err != nil {
 		return err
 	}
 
-	if err := mapFiles(obj, req); err != nil {
-		return err
+	return validate(obj)
+}
+
+type multipartRequest http.Request
+
+var _ setter = (*multipartRequest)(nil)
+
+var (
+	multipartFileHeaderStructType = reflect.TypeOf(multipart.FileHeader{})
+)
+
+// TrySet tries to set a value by the multipart request with the binding a form file
+func (r *multipartRequest) TrySet(value reflect.Value, field reflect.StructField, key string, opt setOptions) (isSetted bool, err error) {
+	if value.Type() == multipartFileHeaderStructType {
+		_, file, err := (*http.Request)(r).FormFile(key)
+		if err != nil {
+			return false, err
+		}
+		if file != nil {
+			value.Set(reflect.ValueOf(*file))
+			return true, nil
+		}
 	}
 
-	return validate(obj)
+	return setByForm(value, field, r.MultipartForm.Value, key, opt)
 }

binding/form_mapping.go

@@ -7,7 +7,6 @@ package binding
 import (
 	"errors"
 	"fmt"
-	"net/http"
 	"reflect"
 	"strconv"
 	"strings"
@@ -16,34 +15,6 @@ import (
 	"github.com/gin-gonic/gin/internal/json"
 )
 
-func mapFiles(ptr interface{}, req *http.Request) error {
-	typ := reflect.TypeOf(ptr).Elem()
-	val := reflect.ValueOf(ptr).Elem()
-	for i := 0; i < typ.NumField(); i++ {
-		typeField := typ.Field(i)
-		structField := val.Field(i)
-
-		t := fmt.Sprintf("%s", typeField.Type)
-		if string(t) != "*multipart.FileHeader" {
-			continue
-		}
-
-		inputFieldName := typeField.Tag.Get("form")
-		if inputFieldName == "" {
-			inputFieldName = typeField.Name
-		}
-
-		_, fileHeader, err := req.FormFile(inputFieldName)
-		if err != nil {
-			return err
-		}
-
-		structField.Set(reflect.ValueOf(fileHeader))
-
-	}
-	return nil
-}
-
 var errUnknownType = errors.New("Unknown type")
 
 func mapUri(ptr interface{}, m map[string][]string) error {
@@ -57,11 +28,29 @@ func mapForm(ptr interface{}, form map[string][]string) error {
 var emptyField = reflect.StructField{}
 
 func mapFormByTag(ptr interface{}, form map[string][]string, tag string) error {
-	_, err := mapping(reflect.ValueOf(ptr), emptyField, form, tag)
+	return mappingByPtr(ptr, formSource(form), tag)
+}
+
+// setter tries to set value on a walking by fields of a struct
+type setter interface {
+	TrySet(value reflect.Value, field reflect.StructField, key string, opt setOptions) (isSetted bool, err error)
+}
+
+type formSource map[string][]string
+
+var _ setter = formSource(nil)
+
+// TrySet tries to set a value by request's form source (like map[string][]string)
+func (form formSource) TrySet(value reflect.Value, field reflect.StructField, tagValue string, opt setOptions) (isSetted bool, err error) {
+	return setByForm(value, field, form, tagValue, opt)
+}
+
+func mappingByPtr(ptr interface{}, setter setter, tag string) error {
+	_, err := mapping(reflect.ValueOf(ptr), emptyField, setter, tag)
 	return err
 }
 
-func mapping(value reflect.Value, field reflect.StructField, form map[string][]string, tag string) (bool, error) {
+func mapping(value reflect.Value, field reflect.StructField, setter setter, tag string) (bool, error) {
 	var vKind = value.Kind()
 
 	if vKind == reflect.Ptr {
@@ -71,7 +60,7 @@ func mapping(value reflect.Value, field reflect.StructField, form map[string][]s
 			isNew = true
 			vPtr = reflect.New(value.Type().Elem())
 		}
-		isSetted, err := mapping(vPtr.Elem(), field, form, tag)
+		isSetted, err := mapping(vPtr.Elem(), field, setter, tag)
 		if err != nil {
 			return false, err
 		}
@@ -81,7 +70,7 @@ func mapping(value reflect.Value, field reflect.StructField, form map[string][]s
 		return isSetted, nil
 	}
 
-	ok, err := tryToSetValue(value, field, form, tag)
+	ok, err := tryToSetValue(value, field, setter, tag)
 	if err != nil {
 		return false, err
 	}
@@ -97,7 +86,7 @@ func mapping(value reflect.Value, field reflect.StructField, form map[string][]s
 			if !value.Field(i).CanSet() {
 				continue
 			}
-			ok, err := mapping(value.Field(i), tValue.Field(i), form, tag)
+			ok, err := mapping(value.Field(i), tValue.Field(i), setter, tag)
 			if err != nil {
 				return false, err
 			}
@@ -108,9 +97,14 @@ func mapping(value reflect.Value, field reflect.StructField, form map[string][]s
 	return false, nil
 }
 
-func tryToSetValue(value reflect.Value, field reflect.StructField, form map[string][]string, tag string) (bool, error) {
-	var tagValue, defaultValue string
-	var isDefaultExists bool
+type setOptions struct {
+	isDefaultExists bool
+	defaultValue    string
+}
+
+func tryToSetValue(value reflect.Value, field reflect.StructField, setter setter, tag string) (bool, error) {
+	var tagValue string
+	var setOpt setOptions
 
 	tagValue = field.Tag.Get(tag)
 	tagValue, opts := head(tagValue, ",")
@@ -132,25 +126,29 @@ func tryToSetValue(value reflect.Value, field reflect.StructField, form map[stri
 		k, v := head(opt, "=")
 		switch k {
 		case "default":
-			isDefaultExists = true
-			defaultValue = v
+			setOpt.isDefaultExists = true
+			setOpt.defaultValue = v
 		}
 	}
 
+	return setter.TrySet(value, field, tagValue, setOpt)
+}
+
+func setByForm(value reflect.Value, field reflect.StructField, form map[string][]string, tagValue string, opt setOptions) (isSetted bool, err error) {
 	vs, ok := form[tagValue]
-	if !ok && !isDefaultExists {
+	if !ok && !opt.isDefaultExists {
 		return false, nil
 	}
 
 	switch value.Kind() {
 	case reflect.Slice:
 		if !ok {
-			vs = []string{defaultValue}
+			vs = []string{opt.defaultValue}
 		}
 		return true, setSlice(vs, value, field)
 	case reflect.Array:
 		if !ok {
-			vs = []string{defaultValue}
+			vs = []string{opt.defaultValue}
 		}
 		if len(vs) != value.Len() {
 			return false, fmt.Errorf("%q is not valid value for %s", vs, value.Type().String())
@@ -159,7 +157,7 @@ func tryToSetValue(value reflect.Value, field reflect.StructField, form map[stri
 	default:
 		var val string
 		if !ok {
-			val = defaultValue
+			val = opt.defaultValue
 		}
 
 		if len(vs) > 0 {