Check for R installations in `/opt/R`

[fmichonneau]

I have:

• searched the issue tracker for similar issues
• installed the latest version of Quarto CLI
• formatted my issue following the Bug Reports guide

Bug description

For our professional products, we recommend having R installed in /opt/R/x.y.z so it's easier to have multiple versions living side-by-side.

When running, quarto check, when R is installed there, it doesn't get detected:

[✓] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/

Would it make sense to also check the /opt directory for a possible R installation?

PS: the same could also probably be done for Python which we also recommend installing in /opt but the system version (in /usr/bingets detected).

Quarto check output

Quarto 1.9.14
[✓] Checking environment information...
      Quarto cache location: /home/ubuntu/.cache/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.6.3: OK
      Dart Sass version 1.87.0: OK
      Deno version 2.4.5: OK
      Typst version 0.13.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.9.14
      Path: /opt/quarto/1.9.14/bin

[✓] Checking tools....................OK
      TinyTeX: (not installed)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Tex:  (not detected)

[✓] Checking Chrome Headless....................OK
      Chrome:  (not detected)

[✓] Checking basic markdown render....OK

[✓] Checking R installation...........(None)

      Unable to locate an installed version of R.
      Install R from https://cloud.r-project.org/

[✓] Checking Python 3 installation....OK
      Version: 3.12.3
      Path: /usr/bin/python3
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with python3 -m pip install jupyter

[✓] Checking Julia installation...

[cderv]

For our professional products, we recommend having R installed in /opt/R/x.y.z so it's easier to have multiple versions living side-by-side.

I understand. Currently we detect which one is active or in PATH. Which one to use if none set in PATH ?
Which folder to choose as x.y.z ?

but the system version (in /usr/bingets detected).

For python, this is possibly the one in PATH, right ?

We can try do better in detection, but we need to agree on what to do exactly as fallback to decide which version to use.

[cderv]

Current logic for R

• Check QUARTO_R env var - if not set...
• Check R_HOME env var - if not set...
• Check for Rscript in PATH - if not set...
• (windows only) check the windows registry