Revert "fix: ignore all unmarshal errors from locale (#673)"

This reverts commit fbf009fe75.

pkg/oidc/types.go

@@ -3,6 +3,7 @@ package oidc
 import (
 	"database/sql/driver"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"reflect"
 	"strings"
@@ -77,18 +78,24 @@ func (l *Locale) MarshalJSON() ([]byte, error) {
 }
 
 // UnmarshalJSON implements json.Unmarshaler.
-// All unmarshal errors for are ignored.
+// When [language.ValueError] is encountered, the containing tag will be set
-// When an error is encountered, the containing tag will be set
 // to an empty value (language "und") and no error will be returned.
 // This state can be checked with the `l.Tag().IsRoot()` method.
 func (l *Locale) UnmarshalJSON(data []byte) error {
 	err := json.Unmarshal(data, &l.tag)
-	if err != nil {
+	if err == nil {
-		l.tag = language.Tag{}
-	}
 		return nil
 	}
 
+	// catch "well-formed but unknown" errors
+	var target language.ValueError
+	if errors.As(err, &target) {
+		l.tag = language.Tag{}
+		return nil
+	}
+	return err
+}
+
 type Locales []language.Tag
 
 // ParseLocales parses a slice of strings into Locales.

pkg/oidc/types_test.go

@@ -234,9 +234,7 @@ func TestLocale_UnmarshalJSON(t *testing.T) {
 		{
 			name:    "bad form, error",
 			input:   `{"locale": "g!!!!!"}`,
-			want: dst{
+			wantErr: true,
-				Locale: &Locale{},
-			},
 		},
 	}