Validation: use lang.Default if no lang option provided

Author: System-Glitch

lang/default.go

@@ -207,6 +207,11 @@ var enUS = &Language{
 	},
 }
 
+// Default language used if no language is provided in a feature's options.
+// By default, equals to the built-in "en-US" language.
+// Although it can be replaced, writing to this variable is not concurrently safe.
+var Default = enUS
+
 // SetDefaultLine set the language line identified by the given key in the
 // default "en-US" language.
 // Values set this way can be overridden by language files.

validation/validator.go

@@ -114,7 +114,10 @@ type Options struct {
 	// To avoid allocating when assigning to an `interface{}`, context keys often have
 	// concrete type `struct{}`. Alternatively, exported context key variables' static
 	// type should be a pointer or interface.
-	Extra    map[any]any
+	Extra map[any]any
+
+	// Language used for translating validation error messages.
+	// Defaults to `lang.Default`.
 	Language *lang.Language
 	DB       *gorm.DB
 	Config   *config.Config
@@ -275,6 +278,9 @@ func Validate(options *Options) (*Errors, []error) {
 	if options.Extra == nil {
 		options.Extra = map[any]any{}
 	}
+	if options.Language == nil {
+		options.Language = lang.Default
+	}
 
 	rules := options.Rules.AsRules()
 	for _, field := range rules {

validation/validator_test.go

@@ -890,6 +890,23 @@ func TestValidate(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "no_language_provided_in_options",
+			options: &Options{
+				Data: map[string]any{"property": nil},
+				Rules: RuleSet{
+					{Path: "property", Rules: List{Required()}},
+				},
+			},
+			wantValidationErrors: &Errors{
+				Fields: FieldsErrors{
+					"property": &Errors{
+						Errors: []string{"The property is required."}, // Translated message (using lang.Default)
+					},
+				},
+			},
+			wantData: map[string]any{},
+		},
 	}
 
 	for _, c := range cases {