I'm not familiar with the planning behind how this API matches the Python classes, but this functionality has been removed from <perspective-viewer> which now only supports the load() method (as described in #1231). I would think this should also be removed from@finos/perspective-jupyterlab, as well as ultimately from the Python PerspectiveViewer API. Because there's no repro or explanation, I'm not sure what is calling update() on the uninitialized TypeScript PerspectiveViewer, whether this is just how the Python PerspectiveViewer code wraps it's constructor initializer, etc..

I understand you've encountered a bug but this Issue is not useful for tracking or planning. Since the tests pass and the /examples I have seem to work, I'm closing it for now. If you have a fix in mind and just want to call out that it is broken, just open a PR and save the indignity for the PR description; or a Draft PR if you just have a failing test case. If you want other developers to help, or to just track and document the problem for later, please open a new Issue with at least some details, so we can collaborate and ultimately fix it.

Its pretty clear, we call viewer.update here and here. That hits this line, but viewer has no default table so this.viewer.table is undefined since document.createElement("perspective-viewer") doesn't create a table. That triggers the error TypeError: this.viewer.table is undefined.

I don't think theres tests around this, but the usual examples were not run as they include loading up a csv or json as demoed in the original PR. Regardless, it is fixed on #1294 which guards the PerspectiveWidget to create a client table if this.viewer.table is undefined.