(The related problem is how best to actually run the Users module, and how it should react in the absence of a Permissions module on the back-end. It's in )

I've updated the <List> component so that it now emits a helpful warning before exploding – because that warning would have saved me two or three hours last night and today. But it still explodes when given a null list to render, because FEFO.

Meanwhile, I have made the Users module robust against making this call – it passes an empty list if `usersPermissions` is null. So the problem has gone away and we can now once more load full records in the Users module. But this exposes another problem, which I will document separately.

With that established, it becomes terribly easy to see what the problem is: line 118 of UserPermissions.js invokes:

But usersPermissions is null.

Two possible fixes: make the <List> component tolerant of begin passed a null list, or fix the Users module to pass an empty one instead. I think I prefer the latter: for the philosophical reason that it's good for <List> to help catch inadvertent invocations will a null list; and for the practical reason that then we don't need to make a new release of stripes-components.

Well, in the end I did yarn link @folio/stripes-components in stripes-core as well as stripes-sample-platform, though I didn't think it could be necessary. Then in desperation, I did it in ui-users as well, since that was the module that was directly provoking the problem. No dice. Finally, I panicked and yarn linked it in ui-items as well – and, bizarrely, that's what it took for me to get the "live" version of stripes-components running.

I really, really wish I understood NPM/Yarn; or even really that I was convinced it's even theoretically understandable.

List.js itself – the proximate cause of the error – is part of stripes-components, which should mean I can add instrumentation there to better understand what is going on. But for some reason, even though I {{yarn link}}ed stripes-components into my platform, it's using a version from the NPM repository. Still investigating.