Shiny apps do not communicate with console

[JosiahParry]

Positron Version:

Positron Version: 2024.07.0 (Universal) build 21
Code - OSS Version: 1.90.0
Commit: 82b335e
Date: 2024-07-09T04:32:26.804Z
Electron: 29.4.0
Chromium: 122.0.6261.156
Node.js: 20.9.0
V8: 12.2.281.27-electron.0
OS: Darwin arm64 23.4.0

Steps to reproduce the issue:

1. Run any shiny app that communicates with the console
2. notice that nothing is being executed
3. Cancel the shiny app
4. notice that the console is still interrupting interrupt again
5. notice everything that was printed was finally printed to the console

What did you expect to happen?

console messages show as they appear

Were there any error messages in the output or Developer Tools console?

[juliasilge]

I think I would recommend either:

• using the Shiny extension (not bundled right now, but installable from OpenVSX) and the "play" button that it offers. That will serve the app from a separate R session and is what I prefer.
• running via shiny::runApp('app-dir') from the console. This is more like what RStudio does, and does behave the way RStudio does in the same situation.

Either one of these will use the Positron Viewer pane.

Can you try one of those out? Or is there a specific reason you are running the Shiny code in the console this way?

[JosiahParry]

Maybe the shiny extension can be helpful here. But I'd like to be a little vanilla with the experience if possible.

Running shiny::runApp() and pointing to the directory which contains the app.R file that I am editing feels somewhat circuitous. In all of the demo applications I've built and ran they've all had the shiny::shinyApp() line at the end

See the example at https://shiny.posit.co/r/getstarted/shiny-basics/lesson1/index.html#cb5

[juliasilge]

It's true that the treatment for running this code interactively line-by-line in the console is somewhat different in RStudio than in Positron so we will take a look.

As a workaround for now, I would recommend using the Shiny extension when developing Shiny apps and using the "Run Shiny App" command, perhaps via the UI and the "Play" button on your app file.

[emilopezcano]

Just in case this is useful: I use shiny modules and a package structure for my shiny apps. Each shiny module includes a function that runs an example application. I don't see the "play" button with this workflow, and the way I can see the prints is running that example app in the terminal:

Rscript -e 'devtools::load_all();intervention_controls_app()'

It would be great having the prints in the R console as in RStudio, though. Thank you all for your work!

[nteetor]

I ran into this problem recently. I created a small test shiny app in a scratch file. I created the ui object, the server object, ran shiny::shinyApp(ui, server) in the console, and saw none of the console output I expected. I thought I was going crazy until today the problem occurred again with an even simpler test app. I performed the same process in RStudio where the expected output appeared in the console.

I can confirm saving my test app to a file and running shiny::runApp(<path/file>) does produce output in the positron console.

I'm confused why the positron console is munching an app's output depending on how the app is launched. The silent nature of the bug(?) is unexpected and frustrating.