fix(web): handle TypeCastError when building form validation messages (#40212)

Fixes https://github.com/go-gitea/gitea/issues/40210

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/web/binding/binding.go

@@ -28,10 +28,13 @@ import (
 )
 
 const (
+	// TODO: need to refactor the binding package, let the rules provide error message directly.
+	// Don't use the fragile Classification and useless&incorrect Message field in the future.
+
 	errContentType     = "ContentTypeError"
 	errDeserialization = "DeserializationError"
 	errTypeCast        = "TypeCastError"
-	errRule            = "RuleError"
+	ErrTypeCast        = errTypeCast
 
 	ErrRequired     = "RequiredError"
 	ErrAlphaDashDot = "AlphaDashDotError"

modules/web/middleware/binding.go

@@ -174,6 +174,8 @@ func BuildValidationErrorForUser(f any, l translation.Locale, bindingErrs valida
 		errorMessage = l.TrString("form.invalid_group_team_map_error", fieldDisplayName, bindingErrMsg)
 	case validation.ErrInvalidBadgeSlug:
 		errorMessage = l.TrString("form.invalid_slug_error", fieldDisplayName)
+	case binding.ErrTypeCast:
+		errorMessage = l.TrString("form.field_invalid_message", fieldDisplayName, bindingErrMsg)
 	default:
 		setting.PanicInDevOrTesting("unknown binding error classification for field %T.%s: %v, err: %s", f, errorFieldName, classification, bindingErrMsg)
 		var msg string

modules/web/middleware/binding_test.go

@@ -4,6 +4,9 @@
 package middleware
 
 import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
 	"testing"
 
 	"gitea.dev/modules/translation"
@@ -12,17 +15,28 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-type testRangeForm struct {
+type testBindingForm struct {
 	FormDefaultValidator
 	Hours int `binding:"Range(0,1000)"`
 }
 
 func TestBuildValidationErrorForUser(t *testing.T) {
-	// an out-of-range value must reach its own message instead of the panicking "default" branch
-	form := &testRangeForm{Hours: 2000}
-	errs := validation.Binder().Validate(t.Context(), form)
-	errorMessage, errorFieldName, fieldNames := BuildValidationErrorForUser(form, translation.MockLocale{}, errs)
-	assert.Equal(t, "form.range_error:form.Hours,0,1000", errorMessage)
-	assert.Equal(t, "Hours", errorFieldName)
-	assert.Equal(t, []string{"Hours"}, fieldNames)
+	t.Run("Range", func(t *testing.T) {
+		form := &testBindingForm{Hours: 2000}
+		errs := validation.Binder().Validate(t.Context(), form)
+		errorMessage, errorFieldName, fieldNames := BuildValidationErrorForUser(form, translation.MockLocale{}, errs)
+		assert.Equal(t, "form.range_error:form.Hours,0,1000", errorMessage)
+		assert.Equal(t, "Hours", errorFieldName)
+		assert.Equal(t, []string{"Hours"}, fieldNames)
+	})
+	t.Run("TypeCast", func(t *testing.T) {
+		req := httptest.NewRequest(http.MethodPost, "/", strings.NewReader("hours=abc"))
+		req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+		form := &testBindingForm{}
+		errs := validation.Binder().Bind(req, form)
+		errorMessage, errorFieldName, fieldNames := BuildValidationErrorForUser(form, translation.MockLocale{}, errs)
+		assert.Equal(t, "form.field_invalid_message:form.Hours,Value could not be parsed as integer", errorMessage)
+		assert.Equal(t, "Hours", errorFieldName)
+		assert.Equal(t, []string{"Hours"}, fieldNames)
+	})
 }