Download uploaded PDFs from Shiny App and delete files on close - r

Question

I have a shiny app that uploads pdfs to do some checks on them and write a report to a table for the user to see. One of the requirements is to create a link to the document that downloads the initial uploaded pdf. Is there a way to access the temp directory files for download and put that download link in a DT datatable? I've tried coping files to www and they can be accessed that way but when the session ends the files are not deleted.
library(shiny)
library(DT)
ui <- fluidPage(
fileInput('pdfFile',
'Upload PDF',
multiple = TRUE,
accept = c('.pdf')),
DTOutput('Table')
)
server <- function(input, output) {
output$Table <- renderDT({
pdfTable <- cbind(input$pdfFile,
pdflink = sprintf('%s',
input$pdfFile$datapath,
input$pdfFile$name,
input$pdfFile$name),
stringsAsFactors = FALSE)
datatable(pdfTable,escape = FALSE)
})
}
shinyApp(ui = ui, server = server)

Answer 1

You can use session$onSessionEnded to execute some code after the client has disconnected (I confess I never tried):
server <- function(input, output, session) {
session$onSessionEnded(function(){
file.remove(......)
})
output$Table <- renderDT({
pdfTable <- cbind(input$pdfFile,
pdflink = sprintf('%s',
input$pdfFile$datapath,
input$pdfFile$name,
input$pdfFile$name),
stringsAsFactors = FALSE)
datatable(pdfTable, escape = FALSE)
})
}

Answer 2

I wasn't able to get the downloadButton to appear in the table, but the otherwise I believe the following meets your requirements. The basic idea is to copy the uploaded file to a new tempfile whose location gets saved in a reactiveVal until needed.
library(shiny)
library(tidyverse)
library(DT)
ui <- fluidPage(
fileInput('pdfFile',
'Upload PDF',
multiple = TRUE,
accept = c('.pdf')),
downloadButton("download_button", "Download Selected File"),
DTOutput('Table')
)
server <- function(input, output) {
output$Table <- renderDT({
uploaded_df() %>%
select(-temp) %>%
datatable(selection = "single")
})
uploaded_df <- reactiveVal(tibble(name = character(), temp = character()))
observeEvent(input$pdfFile,{
temp_file_location <- tempfile(fileext = ".pdf")
file.copy(input$pdfFile$datapath, temp_file_location)
tibble(name = input$pdfFile$name,
temp = temp_file_location) %>%
bind_rows(uploaded_df(), .) %>%
uploaded_df()
})
output$download_button <- downloadHandler(
filename <- function() {
req(input$Table_rows_selected)
uploaded_df()$name[[input$Table_rows_selected]]
},
content <- function(file) {
file.copy(uploaded_df()$temp[[input$Table_rows_selected]], file)
}
)
}
shinyApp(ui = ui, server = server)