fix: ignore empty json strings for locale

pkg/oidc/types.go

@@ -82,6 +82,9 @@ func (l *Locale) MarshalJSON() ([]byte, error) {
 // 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 {
+	if len(data) == 0 || string(data) == "\"\"" {
+		return nil
+	}
 	err := json.Unmarshal(data, &l.tag)
 	if err == nil {
 		return nil

pkg/oidc/types_test.go

@@ -217,6 +217,30 @@ func TestLocale_UnmarshalJSON(t *testing.T) {
 		want    dst
 		wantErr bool
 	}{
+		{
+			name:    "value not present",
+			input:   `{}`,
+			wantErr: false,
+			want: dst{
+				Locale: nil,
+			},
+		},
+		{
+			name:    "null",
+			input:   `{"locale": null}`,
+			wantErr: false,
+			want: dst{
+				Locale: nil,
+			},
+		},
+		{
+			name:    "empty, ignored",
+			input:   `{"locale": ""}`,
+			wantErr: false,
+			want: dst{
+				Locale: &Locale{},
+			},
+		},
 		{
 			name:  "afrikaans, ok",
 			input: `{"locale": "af"}`,
@@ -237,16 +261,17 @@ func TestLocale_UnmarshalJSON(t *testing.T) {
 			wantErr: true,
 		},
 	}
-
 	for _, tt := range tests {
-		var got dst
-		err := json.Unmarshal([]byte(tt.input), &got)
-		if tt.wantErr {
-			require.Error(t, err)
-			return
-		}
-		require.NoError(t, err)
-		assert.Equal(t, tt.want, got)
+		t.Run(tt.name, func(t *testing.T) {
+			var got dst
+			err := json.Unmarshal([]byte(tt.input), &got)
+			if tt.wantErr {
+				require.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			assert.Equal(t, tt.want, got)
+		})
 	}
 }