why is KEYWORDS.db not in '/usr/lib/R/doc/' but in '/usr/share/R/doc/'?

Hello Johan and welcome to R-SIG-Debian!

? Tue, 6 Jun 2023 18:55:27 +0200
Johan Andresen <johan.andresen at gmail.com> ?????:

I feel lucky to have found out that `/doc/KEYWORDS.db` is in
`/usr/share/R/`, not in `usr/lib/R/` where rpy2 in python apparently
looks for it when trying to search help in R from the python
environment. it returned this error: `cannot open file
'/usr/lib/R/doc/KEYWORDS.db': No such file or directory`.

What to do now?
- is this a problem with rpy2 looking for `/doc/KEYWORDS.db` that
should not be in `usr/lib/R/`? -> *edit its script to point at the
correct path?*

It seems that R.home('doc') doesn't return the right path when running
from under rpy2 for some reason. (With Debian packages, it should
return "/usr/share/R/doc", not "/usr/lib/R/doc".)

It's documented in ?R.home that on Unix-like OSes, the function relies
on environment variables like R_DOC_DIR being set during startup.

How does rpy2 launch R? It looks like rpy2 drives an embedded R like a
frontend. I think that at least under Unix-alikes, the required
environment variables are set by launching the frontend via `R CMD
/path/to/frontend/executable` (see WRE 8.1 [*]), except this isn't
convenient for the Python process. I guess rpy2 could obtain the
additional variables the same way it currently extracts LD_LIBRARY_PATH.

Johan
with his first question on a, not just thus, mail list

[[alternative HTML version deleted]]

One tiny detail: this mailing list (and other R project mailing lists)
removes the HTML part of the messages it processes, so it's best to
compose in plain text. But the rest of it you're doing absolutely right!

Best regards,
Ivan

[*]
https://cran.r-project.org/doc/manuals/R-exts.html#Embedding-R-under-Unix_002dalikes