Customui Errors
CustomUiParseError
class
Thrown when a customUI ribbon-customisation part (customUI/customUI.xml or customUI/customUI14.xml) is present but cannot be parsed into a CustomUiDocument: malformed XML, a missing or unrecognised <customUI> root namespace, or nesting deep enough to look hostile. A workbook with no ribbon customisation never produces this: Workbook.customUI is an empty array instead.
The parser treats the part as hostile input (a spreadsheet library parses untrusted files), so a malformed structure fails closed with this error rather than yielding a half-built tree.
ts
class CustomUiParseError extends XlsxError {
override readonly name = 'CustomUiParseError';
override readonly code = 'malformed-input';
}