How to get the Domino Username of a Shiny App Viewer

Prerequisite

An App framework that can access proxied HTTP headers. This is supported by Flask and Dash by default, but is only supported by Shiny if using Server Pro.

Usage: 

Is there a workaround to extract username of R shiny App Viewer if not using Server Pro? 

Resolution:

To extract username from document.cookie in JavaScript and sending that as an input value to Shiny with Shiny.setInputValue, https://shiny.rstudio.com/articles/communicating-with-js.html 

Sample JavaScript snippet other customer used to obtain the username and send it to the R Shiny app. 

var req = new XMLHttpRequest()
// Handle HTTP GET response event
req.addEventListener("load", function() {
// If the HTTP GET failed, log and exit event handler early
if (this.status !== 200) {
console.error("Failed to retrive username with HTTP code", this.status)
// Maybe set a default username?
Shiny.setInputValue('username', 'anonymous')
return
}
// Parse the returned JSON and retrive the username
var response = JSON.parse(this.responseText)
var username = response.canonicalName
console.log("Your username is:", username)
// Send username to Shiny
// https://shiny.rstudio.com/articles/communicating-with-js.html
Shiny.setInputValue('username', username)
})
// Send the HTTP GET request
req.open('GET', '/v4/auth/principal')
req.send()