Get imputed URL for current app/session

[hadley]

Code original written by @jcheng5 for r-lib/gargle#157, but I think it makes the most sense for it to live in Shiny, given that y'all know the most about how to derive this url. I have zero clue how to test this. I made the following simple app, but then couldn't think how to deploy it + dev shiny in such away that it would run on shinyapps or RSC.

library(shiny)
ui <- fluidPage(
  textOutput("url")
)
server <- function(input, output, session) {
  output$url <- renderText(session$getUrl())
}
shinyApp(ui, server)

[jcheng5]

There's actually (more reliable?) data available on clientData, as it's basically the browser telling the server what it's got in the URL bar:

shiny/srcts/src/shiny/init.ts

Lines 460 to 466 in 7e4248b

	initialValues[".clientdata_url_protocol"] = window.location.protocol;
	initialValues[".clientdata_url_hostname"] = window.location.hostname;
	initialValues[".clientdata_url_port"] = window.location.port;
	initialValues[".clientdata_url_pathname"] = window.location.pathname;
	// Send initial URL search (query string) and update it if it changes
	initialValues[".clientdata_url_search"] = window.location.search;

library(shiny)

ui <- fluidPage(
  textOutput("url")
)

server <- function(input, output, session) {
  output$url <- renderText({
    paste0(
      session$clientData$url_protocol,
      "//",
      session$clientData$url_hostname,
      ":",
      session$clientData$url_port,
      session$clientData$url_pathname,
      if (nzchar(session$clientData$url_search)) "?",
      session$clientData$url_search
    )
  })
}

shinyApp(ui, server)

I think I did not use this for gargle because I needed the URL while handling an HTTP request (i.e. in the UI), not from the server function.

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