upload_file respects multiple argument in fileInput (unlike browsers)

[TymekDev]

Context

Just recently I have learned that multiple = TRUE in fileInput is just a hint and is entirely enforced by the browser. For example, here is a short example of bypassing this limitation by dragging files:

CleanShot.2023-12-13.at.16.46.37.mp4

I have implemented a server-side validation to ensure that user uploads only a single file. If there is more than one file, then an error message is displayed. I want to write a test using {shinytest2} to check if a correct message is displayed.

Issue

Given a fileInput("f", multiple = FALSE) and the following {shinytest2} code only first file will make it to input$f during testing.

library(shinytest2)
app <- AppDriver$new()
app$upload_file(f = c("file1", "file2"))

However, if we provide multiple = TRUE, then both files will appear in input$f.

Reprex

tymek@maczek ~/w/r/reprex > Rscript test-shinytest2.R
Loading required package: testthat
   name size type datapath
1 file1    0             0

tymek@maczek ~/w/r/reprex > MULTIPLE=TRUE Rscript test-shinytest2.R
Loading required package: testthat
   name size type datapath
1 file1    0             0
2 file2    0             1

app.R

library(shiny)

shinyApp(
  tagList(
    fileInput("f", "", multiple = as.logical(Sys.getenv("MULTIPLE", FALSE))),
    verbatimTextOutput("t")
  ),
  function(input, output, session) {
    output$t <- renderPrint({
      print(input$f)
    })
  }
)

test-shinytest2.R

library(shinytest2)

app <- AppDriver$new(".")
app$upload_file(f = c("~/Documents/untitled folder/file1", "~/Documents/untitled folder/file2"))
print(app$get_value(input = "f"))