Daemon mode breaks RSelenium's navigate() method

[cpsievert]

For animint, we've been using servr and RSelenium to test whether plots are rendered in the browser the way we expect. Plot rendering requires a file server, so before I discovered the new daemon support, I did something like:

library(servr)
library(RSelenium)
cmd <- "R -e \'cat(Sys.getpid(), file=\"pid.txt\"); servr::httd(dir=system.file(\"examples/make1\", package=\"servr\"), port=4848, browser=FALSE)\'"
system(cmd, wait = FALSE)
# start selenium server, open firefox, and navigate to file server on localhost
checkForServer(dir=system.file("bin", package = "RSelenium"))
startServer()
remDr <- remoteDriver(browserName = "firefox")
remDr$open(silent = TRUE)
remDr$navigate("http://localhost:4848/")
# kill the file server
tools::pskill(readLines("pid.txt", warn = F))

However, I run into problems if I use daemon=TRUE

res <- httd(dir = system.file("examples/make1", package = "servr"), 
            daemon = TRUE, port = 4848, browser = FALSE)
# The line below freezes firefox & the R session. However, it works if I _manually_ navigate there
# I can also use other methods like `remDr$getPageSource()`
remDr$navigate("http://localhost:4848/")

Any ideas why the daemon approach might cause this problem? Is there a somewhat simple explanation of the difference between the two approaches? Maybe @johndharrison could help? I don't think it's a browser issue as I've also tested this with phantomjs.

[yihui]

I'm in China this month, and I'm behind the Great Fire Wall. It's inconvenient for me to download Selenium, so I have no idea here.

[cpsievert]

No worries. I can always go with the first approach. Enjoy China!

[johndharrison]

This seems to be an issue when RStudio is used as an IDE. Using the RGui or command line R I don't seem to encounter this issue.

library(RSelenium)
library(servr)
remDr <- remoteDriver(browserName = "chrome")
remDr$open(silent = TRUE)
res <- httd(dir = system.file("examples/make1", package = "servr"), 
            daemon = TRUE, port = 4848, browser = FALSE)

remDr$navigate("http://localhost:4848/")

The navigate method completes for me in the background what I observe is RStudio "R Session Aborted".