What does it mean when I see "ERROR CLIENT EXCEPTION" in the RStudio Workbench logs?

Question:

I am seeing a bunch of errors like the below, what does it mean?

[rserver] ERROR CLIENT EXCEPTION (rsession-xxxxxxx): (TypeError) : Cannot read property

Answer:

Client exception errors mean there's a problem on the front end (i.e. a bug or unexpected condition in the JavaScript for the IDE in the browser). These can have useful diagnostic information for troubleshooting problems happening in the browser. In general, if there are no other issues being experienced, these errors can be ignored but if there are problems in the IDE, these errors can tell the user what that problem might be and where to look for a solution.