Detecting opened Shiny code and show Run Shiny App button

[brb-arraytools]

RStudio automatically detects the currently opened .R file. If the file contains Shiny code, it shows a “Run App” button; if it’s a regular R script, it shows a “Run” button instead. It would be great if the extension could similarly detect the type of file that’s open and display the appropriate run button.

[gadenbuie]

It does! Could you describe the case where you didn't see this happening? It's all a bunch of heuristics (both in the Shiny extension and in RStudio) and they are slightly different. The Shiny VS Code extension convention is essentially:

1. An R or Python script that in the form app.R, app-*.R, app_*.R, *-app.R or *_app.R (same for .py files) or exactly ui.R or server.R.
2. The word shiny appears in the contents of the file.

[brb-arraytools]

Thank you for the reply. I was transferred from posit-dev/positron#11376.

1. If I rename my R Shiny code file to be app.R, the Positron run button on the up left will have the choice: Run Shiny App.
2. If I rename my R Shiny code file to be bug.R, the Positron run button on the up left will not have the choice: Run Shiny App. In the R file, the first line is library(shiny). It contains the word "shiny".

[gadenbuie]

Right, both conditions need to be true for the Shiny extension to decide that the file is a runnable Shiny app. It's slightly different than RStudio's handling of Shiny app files and it took me some time to get used to, too. But in the long run, I've found that it's a reasonable constraint, it's easy to rename the file to follow the conventions -- e.g. app-bug.R -- and it avoids edge cases where you wouldn't want the extension to engage.

[brb-arraytools]

I see and good to know that. Thanks for explaining.

[dataspun]

@gadenbuie the two conditions don't seem reliable. I have a file named shiny-run.R for which Positron renders the button in one app, and the exact same file in another app that doesn't render the button.

[gadenbuie]

It's possible that Positron has a different treatment for Shiny apps that kicks in where the Shiny extension doesn't

[juliasilge]

@gadenbuie I don't believe we do, no; we don't have any functionality for Shiny apps beyond what is in the extension.

[gadenbuie]

The play button should always be present, the Shiny VS Code extension just adds an option to "Run Shiny App" to the play button.

As shiny-run.R

As app-run.R

---

@dataspun I can't reproduce the problem I think you're describing, but if you could provide some more information about the differences between those files, we could look into it further.

[dataspun]

@gadenbuie here's the exact same file in a different app (both using R 4.5.1)

The button does not render; apparently some additional conditions are controlling it.

The app otherwise runs if line 3 is executed: shiny::runApp() which is fine but ideally the convenient little button would render reliably.

To your point about heuristics, a copy of the above file renamed app-run.R renders the button as expected but with only one option:

My hunch is there's a package issue -- hopefully this helps reveal what it is and the fix can be documented.

[gadenbuie]

Okay, this is definitely a Positron issue (or it's expected behavior). What you're seeing in the second screenshot is that the Shiny extension is working as expected -- the extension is adding the "Run Shiny App" command to the play button. In the first screenshot with shiny-run.R, the Shiny extension isn't engaging (which is expected behavior of the extension) but Positron itself isn't enabling the play button (that's either unexpected or expected because of other conditions in your workspace).

[juliasilge]

@dataspun can you say more about the workspace where you observe this problem? Is it an R package, with a DESCRIPTION file? We did purposefully hide the UI for the "play" button in posit-dev/positron#4567, because of the discussion in posit-dev/positron#1359.

Does that explain what you are seeing? You can still use the Shiny: Run Shiny App command from the command palette in such a situation.

[dataspun]

@juliasilge that's exactly the issue here. The workspace is an R Shiny app but it has an unused/unnecessary DESCRIPTION file. When I renamed that file to NODESCRIPTION the button renders with expected options. This is the missing condition... not to the ones @gadenbuie highlighted (for Run Shiny App) but to the related confusion around button rendering and options displayed. Cheers!

[juliasilge]

Glad to hear that! We'll keep an eye out for other feedback about whether it's the right call to not show that button in an R package.