I've run into a problem with a fresh shiny install. Launching an app opens a browser window and returns an error from file.path. No information is in the logs and there is no traceback to show what caller is causing the problem.
Listening on http://127.0.0.1:7009
Warning: Error in file.path: cannot coerce type 'closure' to vector of type 'character'
[No stack trace available]
The server is a RHEL 8.2 box with Shiny 126.96.36.199 and the error appears with both R 4.0.1 and R 3.6.3.
My guess is that something on the system is misconfigured but I can't figure out what with so little information returned.