R: The debug pane UX outside of debug sessions is confusing

[lionel-]

The R debugger works differently than the usual debugging experience in VS Code in that the debug session is initiated by R itself rather than by the frontend. This makes usage very smooth but it also means the contents of the debug pane can be confusing, outside of a debug session. There is a big "Run and debug" button that requests the user to find an appropriate extension, leading them on a wrong path. See for instance https://twitter.com/axiomsofxyz/status/1806582669154869580

We should at least provide a launch.json file to hook that "Run and debug" button to display help about debugger usage.

Screen.Recording.2024-06-28.at.09.10.06.mov

[coatless]

@lionel- thanks for the help! I think this was a new addition recently as it was MIA on the last private beta build?

[lionel-]

hmm we've had debug pane support for quite a while. I think if we change the default setting of debug.showInStatusBar to openOnSessionStart this functionality will be much more obvious:

[strengejacke]

How does debugging actually work? When I try to debug a function, Positron says I need to install an extension. When I try to install the R Debugger extension, it says it cannot be installed due to conflicts with Positron built-in features.

[coatless]

@strengejacke the session debug needs to start with a browser() call. Do not use Debug and Run menu directly. You can see an example here: https://youtu.be/p_4ZS-nnQ2Q?t=53

[strengejacke]

How do I use this inside packages? I added browser() into the package function where I wanted to debug, then I ran

library(datawizard)

data(efc, package = "datawizard")
dat <- na.omit(efc)
dat$e42dep <- factor(dat$e42dep)
dat$c172code <- factor(dat$c172code)

debugonce(degroup)
degroup(
  dat,
  select = "c12hour",
  by = c("e42dep", "c172code"),
  suffix_demean = "_within"
)

And got this screen:

[strengejacke]

Nevermind, found it out. I just use browser() too seldom.

[lionel-]

In R packages with C/C++ code, we should provide a launch configuration for clangd that attaches to the pid of the currently running ark session. This would remove the run and debug button for this specific case.

[DanChaltiel]

I am also a bit confused.

I'll use browser() as indicated, but I'm used to breakpoints in RStudio.
I tried all the "breakpoint" menu items in the "run" menu but I couldn't make any of them work, is that intended?
For instance, with an R file opened, I'd hit Run > New breakpoint > Inline breakpoint, and nothing happens, not even an error message.
Are they usable?

[lionel-]

Sorry they are not usable yet.

[DanChaltiel]

@lionel- no problem, but I think it would be better to hide the UI for features that are not usable. Or at least show an error message telling the user about it. I spent some time clicking again and again without understanding 😅