FR: Auto-detect Quarto's bundled pandoc as fallback

[grantmcdermott]

(Potential upstream issue.)

Hi folks.

I just ran into this error on a new laptop, whilst calling some of the btw help documentation tools (e.g., btw_tool_docs_help_page) from the CLI:

Mcp error: -32603: pandoc is required and was not found (see the help page ?rmarkdown::pandoc_available).

The error is obvious enough; I didn't have pandoc installed as a "standalone" binary and available on my PATH (via my package manager). OTOH it's not the full truth, since I do have Quarto installed and this obviously bundles its own pandoc. I can imagine that other users are in a similar boat and this made me think that having a fallback option to / check for Quarto pandoc would be a useful feature.

What do you think about adding automatic detection of Quarto's bundled pandoc as a fallback when rmarkdown::pandoc_available() returns FALSE? Specifically, we could check common Quarto installation paths:

• macOS: /Applications/quarto/bin/tools/pandoc
• Windows: ~/AppData/Local/Programs/Quarto/bin/tools/pandoc
• Linux: /opt/quarto/bin/tools/pandoc

If found we could set Sys.setenv(RSTUDIO_PANDOC = <path>) to make it available to rmarkdown during this session?

[gadenbuie]

hmm I'm kind of surprised rmarkdown::pandoc_available() doesn't do that already? I'll ask my friends on the Quarto team if they have any recommendations before we go down this path, but this seems pretty reasonable to me.

[grantmcdermott]

Super, thanks @gadenbuie.

[gadenbuie]

Let's wait for this issue in the pandoc R package to come through; we can either use that version or inline a local copy until we're ready to take a full dependency on pandoc.

• Add a function to look for pandoc in all known place by this package cderv/pandoc#49