[#2763] fixed multipart/form-data array value bind

tools/rest/multi_binder.go

@@ -5,9 +5,11 @@ import (
 	"encoding/json"
 	"io"
 	"net/http"
+	"reflect"
 	"strings"
 
 	"github.com/labstack/echo/v5"
+	"github.com/spf13/cast"
 )
 
 // BindBody binds request body content to i.
@@ -28,10 +30,12 @@ func BindBody(c echo.Context, i interface{}) error {
 			return echo.NewHTTPErrorWithInternal(http.StatusBadRequest, err, err.Error())
 		}
 		return nil
-	default:
-		// fallback to the default binder
-		return echo.BindBody(c, i)
+	case strings.HasPrefix(ctype, echo.MIMEApplicationForm), strings.HasPrefix(ctype, echo.MIMEMultipartForm):
+		return bindFormData(c, i)
 	}
+
+	// fallback to the default binder
+	return echo.BindBody(c, i)
 }
 
 // CopyJsonBody reads the request body into i by
@@ -57,3 +61,69 @@ func CopyJsonBody(r *http.Request, i interface{}) error {
 
 	return err
 }
+
+// This is temp hotfix for properly binding multipart/form-data array values
+// when a map destination is used.
+//
+// It should be replaced with echo.BindBody(c, i) once the issue is fixed in echo.
+func bindFormData(c echo.Context, i interface{}) error {
+	if i == nil {
+		return nil
+	}
+
+	values, err := c.FormValues()
+	if err != nil {
+		return echo.NewHTTPErrorWithInternal(http.StatusBadRequest, err, err.Error())
+	}
+
+	if len(values) == 0 {
+		return nil
+	}
+
+	rt := reflect.TypeOf(i).Elem()
+
+	// map
+	if rt.Kind() == reflect.Map {
+		rv := reflect.ValueOf(i).Elem()
+
+		for k, v := range values {
+			if total := len(v); total == 1 {
+				rv.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(normalizeMultipartValue(v[0])))
+			} else {
+				normalized := make([]any, total)
+				for i, vItem := range v {
+					normalized[i] = vItem
+				}
+				rv.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(normalized))
+			}
+		}
+
+		return nil
+	}
+
+	// anything else
+	return echo.BindBody(c, i)
+}
+
+// In order to support more seamlessly both json and multipart/form-data requests,
+// the following normalization rules are applied for plain multipart string values:
+// - "true" is converted to the json `true`
+// - "false" is converted to the json `false`
+// - numeric (non-scientific) strings are converted to json number
+// - any other string (empty string too) is left as it is
+func normalizeMultipartValue(raw string) any {
+	switch raw {
+	case "true":
+		return true
+	case "false":
+		return false
+	default:
+		if raw[0] >= '0' && raw[0] <= '9' {
+			if v, err := cast.ToFloat64E(raw); err == nil {
+				return v
+			}
+		}
+
+		return raw
+	}
+}