[Feature Request] Allow to pass URL parameters to runApp() and/or shinyApp()

[ColinFay]

Context

I have a shiny app that behaves differently based on url parameters passed to it

Pain point

When building this app, every time I relaunch the app, I need to refresh the browser with the url parameters included (either manually, or via a development widget built just for that purpose).

Feature Request

I'd love to be able to do something like:

runApp( urlParams = c(x = "xyz", a = "abcd") )

From reading the source code, it seems that this can be done here in runApp:

appUrl <- paste("http://", browseHost, ":", port, sep = "")

with something like

appUrl <- paste("http://", browseHost, ":", port, sep = "")
if (!is.null(urlParams){
appUrl <- paste(
  appUrl, 
  "?",
	paste(
      names(urlParams),
      urlParams, 
      sep = "=", 
      collapse = "&"
    )
}

Let me know what you think, happy to do a PR!

Edit: this might be better to have it inside shinyApp() instead of runApp()

[jcheng5]

Hmmm, I was going to suggest shiny::devmode(TRUE) which enables autoreload (browser automatically reloads when you save .R file)... but I assume you're using golem and probably autoreload doesn't work with packages?

[ismirsehregal]

I recently gave a related answer here.

I think using updateQueryString would be an option:

library(shiny)

ui <- fluidPage(
  selectInput("selection", "Selection", choices = LETTERS[1:3], selected = "A")
)

server <- function(input, output, session) {
  observeEvent(input$selection, {
    newURI <- paste0(
      session$clientData$url_protocol,
      "//",
      session$clientData$url_hostname,
      ":",
      session$clientData$url_port,
      session$clientData$url_pathname,
      "#",
      input$selection
    )
    updateQueryString(newURI, mode = "replace", session)
  })
}

shinyApp(ui, server)

[ismirsehregal]

Another option is to pass a custom function to launch.browser - from ?runApp:

launch.browser
If true, the system's default web browser will be launched automatically after the app is started. Defaults to true in interactive sessions only. This* value of this parameter can also be a function to call with the application's URL.

*typo in the docs

An example:

library(shiny)

ui <- fluidPage(uiOutput("queryString"))

server <- function(input, output, session) {
  output$queryString <- renderUI({
    HTML(paste0(
      parseQueryString(session$clientData$url_search),
      collapse = "<br>"
    ))
  })
}

app <- shinyApp(ui, server)

runApp(
  appDir = app,
  port = 3838,
  launch.browser = function(appUrl) {
    url <- paste0(appUrl, "/?param1=val1&param2=val2#hash")
    invisible(.Call("rs_shinyviewer", url, getwd(), "browser", NULL, PACKAGE = "(embedding)"))
    # utils::browseURL(url) # alternative
  },
  host = "0.0.0.0"
)

Nevertheless, a more user-friendly way to do this would be highly appreciated.