Text to be written must be a length-one character vector

Question

After installing the new version of shiny (1.4.0) package, I face a strange error message

> Warning: Error in writeImpl: Text to be written must be a length-one
> character vector   [No stack trace available]

I do not really understand what has been changed? And how to fix this issue?

Any idea would be highly appreciated!

The Trace looks as follows:

13: execCallbacks(timeoutSecs, all, loop$id)
12: force(expr)
11: with_loop(loop, invisible(execCallbacks(timeoutSecs, all, loop$id)))
10: run_now(timeoutMs/1000, all = FALSE)
9: service(timeout)
8: serviceApp()
7: ..stacktracefloor..(serviceApp())
6: withCallingHandlers(expr, error = doCaptureStack)
5: domain$wrapSync(expr)
4: promises::with_promise_domain(createStackTracePromiseDomain(), 
       expr)
3: captureStackTraces({
       while (!.globals$stopped) {
           ..stacktracefloor..(serviceApp())
       }
   })
2: ..stacktraceoff..(captureStackTraces({
       while (!.globals$stopped) {
           ..stacktracefloor..(serviceApp())
       }
   }))
1: runApp("Projects/Bomboleo")

No traceback available 

Answer 1

One line in my codes is, c("text/csv","text/comma-separated-values,text/plain",".csv") It creates the same problem, because it passes the three text arguments.
Thus, I just rewrite it looking like c(".csv"), now it passes one text only! No more error now in my Shiny App!!

This error happens on UI part only.

Answer 2

I had the same problem, but after playing around with removing the spaces behind some of the commas it finally worked for me! So my advise is to restructure your code, R probably doesn't recognize it due to some spaces at the end of a line of code