webr::global_prompt_install() not working with webR.evalR()

[christianp]

The WebR support package has a function webr::global_prompt_install() which will interactively prompt you to install a package before loading it.
Is there a way of getting WebR to automatically install packages without a prompt? Or could I write my own shim round library() to do this?

[georgestagg]

The webr::global_prompt_install() command takes an argument show_menu. When this is set to FALSE, webR should skip the menu and just attempt to download the package instead.

[christianp]

Ah, thanks!

[georgestagg]

[..] install packages in an allowed list [...]

Ah, I just saw this part of the question! There's no support for an allow-list, I think you'd have to implement that yourself.

You might be able to use renv::dependencies() as an alternative to shimming require() and library(), then once you have your list filter it down and use webr::install() in R or webR.installPackages().

[christianp]

Hrm: when I run that, I get "WebRWorkerError: should not be called with handlers on the stack".
Here's a minimal page that just loads webR and tries to run webr::global_prompt_install(): https://darkened-opalescent-asphalt.glitch.me/
Clearly I'm doing something wrong, but what?

[georgestagg]

Ah yes, there's a gap in documentation here, sorry. To install the new global error handler we have to temporarily turn off webR's other built-in error and warning capturing handlers.

Try with:

await webR.evalRVoid(`webr::global_prompt_install(FALSE)`, { withHandlers: false });

I'll reopen this to remind me to document it.

[georgestagg]

I've done some experimentation, and I can't seem to get this working with evalR(), though I'm sure it worked at some point. Possibly it breaks when using the PostMessage channel since that implements a limited version of the built-in R REPL.

It does seem to work when using writeConsole() and pumping .read() for output. But with that method, you can't get R object references back, just output messages.

  const webR = await new WebR();
  await webR.init();
  await webR.evalRVoid(`webr::global_prompt_install(FALSE)`, { withHandlers: false });
  await webR.writeConsole(`library(dplyr)`);
  for (;;) {
    const output = await webR.read();
    switch (output.type) {
      case 'stdout':
        console.log(output.data)
        break;
      case 'stderr':
        console.log(output.data);
        break;
      case 'prompt':
        console.log(output.data);
        break;
      default:
        console.error(`Unimplemented output type: ${output.type}`);
        console.error(output.data);
    }
  }

(https://terrific-coordinated-parrot.glitch.me/)

EDIT: yes, this is clearly not working right. Even here two invocations of library(dplyr) are needed to actually load the package.

Probably it's best to stick with your own method around shimming library() to run webr::install() for now, and I'll take a look at this when I can. It's likely we'll have to replace the global handler method with a shimming method instead.

[georgestagg]

For completeness, something like this should allow you to shim library() for the moment,

const webR = await new WebR();
await webR.init();
await webR.evalRVoid(`
  .e <- new.env()
  .e[["library"]] <- function (pkg, ...) {
    package <- as.character(substitute(pkg))
    if (!require(package)) webr::install(package)
    base::library(package, character.only = TRUE, ...)
  }
  attach(.e, name = "library_shim", warn.conflicts = FALSE)
`);
await webR.evalR(`library(dplyr)\nprint(starwars)`);

(https://southern-parallel-form.glitch.me/)