Using RStudio with Github Classroom - long version

Classroom

For those that want to know more about the capabilities of Github Classroom, I recommend you start here.

As soon as I knew about it, I felt that I should use it. Don’t ask me why. But, as I mainly use R for working, I quickly realized that RStudio was not one of the ‘off the shelf’ options for Online IDE. I was even surprised that one of the options is MS MakeCode.

Using RStudio

So that’s why I had to find a way thru this.

First, I tried to find a way to integrate RStudio Cloud with Github Classroom. No deal. RStudio Cloud has no API that can trigger a New Project. It requires you to copy the link and fill the form:

The current solution uses mybinder.org as the cloud service that will create our RStudio session. If someone finds out how to use RStudio Cloud automatically, please, send me a message. I’m looking forward to using that.

Before coming out with the current solution, I just put a binder badge on assignment README and realize that mybinder also needs a hand to figure out the repository we want to use.

Then I started to look at how to change the README programmatically when the student forks the assignment. The first thing that came into my mind was GitHub’s actions. The first attempt failed. My bad.

Then I found that CloudFlare had something I could use: Workers.

Essentially, I get a static link, and the user is redirected to the custom link in mybinder.org. I had to take leverage on the referer header to work out. Here was the code:

const base = "https://mybinder.org/v2/gh"
const postfix = "/master?urlpath=rstudio"
const statusCode = 302

async function handleRequest(request) {

  const url = new URL(request.headers.get('referer'))

  const { pathname, search, hash } = url

  const destinationURL = base + pathname + postfix

  return Response.redirect(destinationURL, statusCode)
}

addEventListener("fetch", async event => {
  event.respondWith(handleRequest(event.request))
})

It worked fine. Did the job. But I had another problem: speed.

Every time the student clicks on the mybinder badge, mybinder started to build the environment from scratch. One of the suggestions from mybinder howto is “Ensure your repository gets a lot of clicks”. Sure. That works because after the environment is built, the next launch is fast. But the students need to push changes in the code to check if the answer is right (considering Github’s auto-grading).

Digging here, digging there, I found a nice Github Action called repo2docker that deserves to be mentioned. It does the following: pre-build the docker in Github’s realm and caches it on mybinder that finishes the build. This action is triggered as soon as the student forks the assessment or pushes any change. This action is still being used in my current solution, but not in the assignment itself.

Another suggestion from mybinder howto was “Use two repositories: one for the environment, one for your content”. That I missed entirely on the first time, but not in the second. Clever! So I moved all the mybinder code from the assessment itself and built a template just for the RStudio environment. Once I push (rarely) some change to that repository, it triggers the build, and it’s done.

But now I had another problem. This new setup leverages on nbgitpuller that pulls the assessment repository into the mybinder session just before the session launch. First thing, the assessment repository must be public since I could not find a way to give credentials to nbgitpuller (anybody?). Second, the link that was generated by the nbgitpuller website is adorable. So I had to (again) try the CloudFlare hack to make it work.

Finally, I went again to the Github Actions topic to learn more about it, and I found that what I was doing with CloudFlare could be done with Github Actions.

My first attempt was using the Action Dynamic Readme, which did the job pretty well. But I realized I would like to have some in-house code to deal with this matter. Don’t get me wrong, but my problem was that the current action was too big for what I needed. It depends on another action to expose several variables, and the main code was done using the Docker approach and, to my surprise, PHP. This fellow actually did a great job creating an action-toolkit for PHP. Well, there was too much code for me to keep track of security issues, then I did it. Yes, I did code my own action. Here is the link. It’s JavaScript, simple, basic, unsophisticated, ordinary, but does the job, fast.

And now we can start with the tutorial:

<a href="https://mybinder.org/v2/gh/YOUR_USERNAME/YOUR_FORK/main?urlpath=git-pull%3Frepo%3Dhttps%253A%252F%252Fgithub.com%252F${REPOSITORY_ACCOUNT}%252F${REPOSITORY_SLUG}%26targetPath%3DYOUR_CLASSROOM%26urlpath%3Drstudio%252F%26branch%3Dmain">
  <img src="https://mybinder.org/badge_logo.svg" alt="Launch Binder"/>
</a>

if: contains(github.event.head_commit.message, 'Classroom')

echo "Running tests..."

if Rscript --vanilla .assets/scripts/test.R ; then
 echo "Pass: Program exited zero"
else
 echo "Fail: Program did not exit zero"
 exit 1
fi

echo "All tests passed."

exit 0