Cannot open browser from callr process

[wlandau]

callr::r(function() browseURL("https://github.com")) does not open a browser window even though browseURL("https://github.com") does. This is relevant for non-blocking Shiny apps, e.g. shiny::runApp(launch.browser = TRUE).

[wlandau]

Motivation: https://github.com/wlandau/targets/pull/248. My workaround is to launch the app in r_bg() and then call browseURL() from the parent process, but it is not perfect because the browser usually launches before the app can initialize. I am not sure how shiny::runApp() avoids this problem.

[gaborcsardi]

That is intentional:

callr/R/rcmd.R

Line 106 in 5cf65b9

R_BROWSER = "false",

For the early use cases we did not want subprocesses to open browsers. It is somewhat different nowadays, but probably too late to change.

Workaround:

callr::r(
  function() browseURL("https://github.com"), 
  env = c(R_BROWSER = Sys.getenv("R_BROWSER"))
)

[wlandau]

Thanks, @gaborcsardi. That's totally fair.

I actually figured out a different workaround that does not require R_BROWER:

• Child: pass the host and port to options in shinyApp().
• Parent: ping the port until it is up, then call browseURL().

Currently using this in targets::tar_watch() and proffer::serve_pprof().