getParseData returns NULL when published in a shiny app to Rstudio Connect

[aaron-horowitz]

Hi everyone,

I asked this question in Rstudio Support, but they were pointing me to standard help files and docs, which I've already gone through. I have a shiny app that parses the ui.R file and, along with getParseData and a bit of tidyverse magic, neatly turns the ui into a dataframe where I can store and use metadata like labels, defaults, etc.

When I run locally/in rstudio server, the function works great. However, when I publish to connect, it breaks my app as the getParseData function returns NULL. Reprex below

parse_ui <- function(.file = here::here("ui.R")){

  file_text <- readLines(.file)
  parsed_ui <- parse(text = file_text)
  parsed_ui_data <- utils::getParseData(parsed_ui, includeText = TRUE)
  print(paste("Is parsed UI NULL? : ",is.null(parsed_ui)))
  print(paste("Is parsed UI Data NULL? : ",is.null(parsed_ui_data)))

  return(parsed_ui_data)
}

I have a simple hack -- add an if else is.null to the function above such that when the file runs locally, write it to a feather file and when its published / returning NULL, read the last saved version instead, but that isn't a bulletproof solution.

Any ideas why this isn't working or better solutions would be appreciated!

Aaron

[andrie]

This probably happens because of the way sandboxing on Connect provides separation between processes and users.

Also, using parsing your source code to define configuration settings sounds like an anti-pattern to me. A better pattern would be to define all your metadata and settings in a configuration file, then let the shiny app itself adjust to the config file.

A great way to do this is to use the config package. See also the managing credentials section of https://db.rstudio.com/.

[cole]

Yes, I suspect the problem is the here::here() piece. If I remember correctly, I have seen the here package have some weird effects on Connect.

Why don't you try just using a relative path from the base of the Shiny application and see if that fixes the problem?

As a debugging step, I would add debugging statements like message(getwd()) and message(.file) to get a better picture of what is happening inside of Connect. As @andrie mentioned, the sandboxing process may be a part of the problem here... or perhaps something needs to be tweaked in the here package.

[aron]

The problem is with the keep.source option, which is not TRUE in all environments.

Running R standalone:

R --slave -e 'getOption("keep.source")'
# => [1] FALSE

You can either set the keep.source option:

  options(keep.source = TRUE)
  parsed_ui <- parse(text = file_text)

Or specify the keep.source argument:

  parsed_ui <- parse(text = file_text, keep.source = TRUE)