R Shiny: Analysing user data in deployed app - r

Question

I am finally trying to make a Shiny app. I am trying to upload a .xlsx file to the app, and then apply some analysis and download the output as a separate .xlsx file. The code for analysis and taking output works when run directly outside Shiny and I use it on daily, so I am simply trying to call it via source and save the duplicated work. Here is what I am trying with Shiny.
I was having problems in calling the file from the W2S.R script, while avoiding errors. I found a way to avoid the errors. The below code is a barebones model of that. However, now I cannot get the actual input to work (Output works fine, one table output on-screen and one XLSX output off-screen).
I am using W2S <- input$W2S1 inside W2S.R script, but it is not recognising the variable input, which it does if used in the server function directly. How do I get it to work inside the script? Or is there any other workaround?
library(shiny)
ui <- fluidPage(
titlePanel(h1("Goods In Transit Analysis", align="center")),
sidebarLayout(
sidebarPanel(
fileInput("W2S1", label="Select GIT W2S file")
),
mainPanel(
tableOutput("contents")
)
)
)
server <- function(input, output) {
output$contents <- renderTable(if(is.null(input$W2S1)){return(NULL)}
else{source("./W2S.R")})
}
shinyApp(ui = ui, server = server)
I will update once I get the input to work. Please help.
EDIT: Made some progress, as noted above. So updated the new code.

Answer 1

Finally nailed it. I needed an observe function and use the $datapath argument.
library(shiny)
ui <- fluidPage(
# Application title
titlePanel(h1("Goods In Transit Analysis", align="center")),
# Sidebar iputs
sidebarLayout(
sidebarPanel(
fileInput(inputId="W2S", label="Select GIT W2S file")
),
# On Screen output
mainPanel(
h3(textOutput("filePath")),
tableOutput("contents")
)
)
)
# Underlining code for output
server <- function(input, output) {
observe({
source("./Code/W2S.R")
W2S <- input$W2S
output$contents <- renderTable(if(is.null(W2S)){return(NULL)}
else{W2S_F(W2S$datapath)})
})
}
# Run the application
shinyApp(ui = ui, server = server)