describeThrowable function
Footer-safe rendering of error: its runtime type, then its
credential-scrubbed message clipped to kMaxDetailLength.
Never returns an empty string — a footer that says harness_error must
always say WHY, including when nothing was recorded.
Implementation
String describeThrowable(Object? error) {
if (error == null) return 'unclassified: no exception recorded';
final String message = scrubCredentials(error.toString());
final String clipped = message.length > kMaxDetailLength
? '${message.substring(0, kMaxDetailLength)}…'
: message;
return '${error.runtimeType}: $clipped';
}