Copy tutorial folder to temp folder when calling `run_tutorial`

[schloerke]

See rstudio/rstudio#6583

Paraphrasing...

learnr attempts to render the learnr document directly in the installed package's folder. We need to check for write permissions and instead copy + run within the R temporary directory (since learnr + learnr-using packages might be installed into an R library that the running user doesn't have write access to)

cc @kevinushey @trestletech

[bhogan-mitre]

Could this be as simple as passing render_args <- list(output_dir = tempdir()) as argument to rmarkdown::run?

Here's a commit that does that.

For example, with run_tutorial("slidy", "learnr"), that produces:

Output created: /tmp/RtmpYSUQAT/slidy.html

[bhogan-mitre]

Actually this needs a bit more work in the intended environment (system library with unprivileged user).

Error in file(con, "w") : cannot open the connection In addition: Warning message: In file(con, "w") : cannot open file 'slidy.knit.md': Permission denied

I will try to clean it up and submit a PR if I can confirm it's working properly.

[bhogan-mitre]

Okay, I did get this to work as intended as an unprivileged user with learnr in the system library.

processing file: slidy.Rmd
...

output file: /tmp/RtmpOj37CC/slidy.knit.md
...

Output created: /tmp/RtmpOj37CC/slidy.html

PR forthcoming with the patch, if you're open to it. Thanks in advance for considering.

[schloerke]

@bhogan-mitre Thank you for looking into this error!

One thing that we will want to try to do is maintain the current save location as it will exist after R shuts down / computer restart. By always storing it as a temp file, then a lot of shiny-prerendered functionality is turned into a standard Rmd file.

If we could check that we have write privileges in the expected location, we should leave the Rmd output as is. If we do not have write privileges, setting the output to a temp dir is a great solution.

PRs are always welcome!!

[jcheng5]

Hmmm, is it ever a good idea to write into a package library (other than, like, actually installing/updating/removing a package)? Seems wrong somehow!

[homerhanumat]

How is this coming along? (For now I suppose just ask students to install the tutorial-endowed package into their User Library and use learnr:run_tutorial() in the Console.)

[schloerke]

@homerhanumat Unfortunately stalled for the moment.

---

Update on approach: Use a cache disk location and copy the tutorial directory, then compile in there.

Ex tutorial directory: file.path(rappdirs::user_data_dir(), "R", "learnr", "tutorial", "package") similar to

learnr/R/storage.R

Line 277 in 9dfe4a9

file.path(rappdirs::user_data_dir(), "R", "learnr", "tutorial", "storage")

with the file location being something like

`rappdirs::user_data_dir()`/R/learnr/tutorial/package/learnr/hello/*

This would allow for tutorial output to persist between R sessions and not build them in the installed folder.

This cache folder could be checked for being able to write and could failover to the temp folder.