diagnostics property
Where store read failures go, with stack traces, like in the rest of the library: usually the root's channel (RootLogger.diagnostics), so the handler set on the root also sees viewer failures. There is no default: the viewer is not attached to the root and cannot obtain the channel itself, and a forgotten parameter would silently send failures to the console. For a prototype pass DiagnosticReporter.console explicitly. The user sees the failure through loadError and loadMoreError.
Implementation
final DiagnosticReporter diagnostics;