rmarkdown::render errors when compiling tex to pdf, with png figure created using python code in French locale

[tdhock]

Hi! first of all, thanks very much for supporting the reticulate package, which I find very useful.
I first tried filing this as rstudio/rmarkdown#2525 (comment) but @yihui says this should be filed here instead.
I am trying to render Rmd to beamer slides on a computer with LC_NUMERIC=fr_FR.UTF-8 meaning that the decimal separator prints as a comma (one half is 0,5).
I expected that I should be able to render rmarkdown to beamer slides, but I observe that there is an error.
The issue is that there is a line in the generated tex file which looks like \includegraphics[width=4,5in]{figure} and that is problematic because pdflatex interprets the comma as a separator between optional arguments in the [ ].
The issue only happens when dev: png is specified in the yaml header.

The work-around that users can do, is to set LC_NUMERIC=C, and then the compilation works fine.
The fix I would suggest in the reticulate/rmarkdown package(s) is to set LC_NUMERIC=C while generating the \includegraphics[width=4.5in]{figure} line.

Below is a minimal reproducible example R script (of course you have to change the RETICULATE_PYTHON line to wherever you have python with matplotlib installed)

cat('---
title: "matplotlib test"
author: "Toby Dylan Hocking"
output: 
  beamer_presentation:
    dev: png
---\n```{r}
Sys.setenv(RETICULATE_PYTHON="/home/tdhock/miniconda3/envs/2023-08-artificial-intelligence/bin/python")
Sys.setlocale("LC_NUMERIC","fr_FR.UTF-8")
(width <- 4.5)\n```\n```{python fig.width=width}
import matplotlib.pyplot as plt
plt.plot([1,2,3,4])
plt.show()\n```
', file="fig-size-bug.Rmd")
rmarkdown::render("fig-size-bug.Rmd")
system("grep 4,5 fig-size-bug.tex")
xfun::session_info("rmarkdown")

When running the code above on my system, the output is shown below:

> rmarkdown::render("fig-size-bug.Rmd")


processing file: fig-size-bug.Rmd
                                                                                                            
output file: fig-size-bug.knit.md

/usr/bin/pandoc +RTS -K512m -RTS fig-size-bug.knit.md --to beamer --from markdown+autolink_bare_uris+tex_math_single_backslash --output fig-size-bug.tex --lua-filter /home/tdhock/lib/R/library/rmarkdown/rmarkdown/lua/pagebreak.lua --lua-filter /home/tdhock/lib/R/library/rmarkdown/rmarkdown/lua/latex-div.lua --highlight-style tango --pdf-engine pdflatex --self-contained 
! Package keyval Error: 5in undefined.

Erreur : LaTeX failed to compile fig-size-bug.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See fig-size-bug.log for more info.
> system("grep 4,5 fig-size-bug.tex")
## [1] 4,5
\includegraphics[width=4,5in]{fig-size-bug_files/figure-beamer/unnamed-chunk-2-1}
> xfun::session_info("rmarkdown")
R version 4.3.1 (2023-06-16)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 22.04.3 LTS


Locale: fr_FR.UTF-8

time zone: America/Phoenix
tzcode source: system (glibc)

Package version:
  base64enc_0.1.3   bslib_0.5.1       cachem_1.0.8      cli_3.6.1        
  digest_0.6.33     ellipsis_0.3.2    evaluate_0.22     fastmap_1.1.1    
  fontawesome_0.5.2 fs_1.6.3          glue_1.6.2        graphics_4.3.1   
  grDevices_4.3.1   highr_0.10        htmltools_0.5.6.1 jquerylib_0.1.4  
  jsonlite_1.8.7    knitr_1.44        lifecycle_1.0.3   magrittr_2.0.3   
  memoise_2.0.1     methods_4.3.1     mime_0.12         R6_2.5.1         
  rappdirs_0.3.3    rlang_1.1.1       rmarkdown_2.25.1  sass_0.4.7       
  stats_4.3.1       stringi_1.7.12    stringr_1.5.0     tinytex_0.48     
  tools_4.3.1       utils_4.3.1       vctrs_0.6.4       xfun_0.40        
  yaml_2.3.7       

Pandoc version: 2.9.2.1

Please note that in the grep command, the first 4,5 is expected, because I set the french locale in my Rmd, so I would like to see that in the generated R code chunk output blocks (but it should be 4.5 in the tex file includegraphics width line).

[tdhock]

this is an issue using current github version

> rmarkdown::render("fig-size-bug.Rmd")


processing file: fig-size-bug.Rmd
                                                                                                            
output file: fig-size-bug.knit.md

/usr/bin/pandoc +RTS -K512m -RTS fig-size-bug.knit.md --to beamer --from markdown+autolink_bare_uris+tex_math_single_backslash --output fig-size-bug.tex --lua-filter /home/tdhock/lib/R/library/rmarkdown/rmarkdown/lua/pagebreak.lua --lua-filter /home/tdhock/lib/R/library/rmarkdown/rmarkdown/lua/latex-div.lua --highlight-style tango --pdf-engine pdflatex --self-contained 
! Package keyval Error: 5in undefined.

Erreur : LaTeX failed to compile fig-size-bug.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See fig-size-bug.log for more info.
> system("grep 4,5 fig-size-bug.tex")
## [1] 4,5
\includegraphics[width=4,5in]{fig-size-bug_files/figure-beamer/unnamed-chunk-2-1}
> sessionInfo()
R version 4.3.1 (2023-06-16)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 22.04.3 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.10.0 
LAPACK: /home/tdhock/miniconda3/envs/2023-08-artificial-intelligence/lib/libmkl_rt.so.2;  LAPACK version 3.10.1

locale:
[1] fr_FR.UTF-8

time zone: America/Phoenix
tzcode source: system (glibc)

attached base packages:
[1] stats     graphics  utils     datasets  grDevices methods   base     

loaded via a namespace (and not attached):
 [1] digest_0.6.33          fastmap_1.1.1          xfun_0.40             
 [4] Matrix_1.6-1.1         lattice_0.22-5         reticulate_1.34.0.9000
 [7] knitr_1.44             htmltools_0.5.6.1      png_0.1-8             
[10] rmarkdown_2.25.1       tinytex_0.48           cli_3.6.1             
[13] grid_4.3.1             withr_2.5.1            compiler_4.3.1        
[16] tools_4.3.1            evaluate_0.22          Rcpp_1.0.11           
[19] yaml_2.3.7             rlang_1.1.1            jsonlite_1.8.7        

[t-kalinowski]

I'm not sure this is reticulate issue, and it's not clear to me what we can do to fix it in reticulate. In reticulate::eng_python() we only read chunk options options$fig.width and options$fig.height and pass them through to the appropriate python contexts for rendering plots; we don't munge on the options any further, and return them unmodified.

I think this might be a knitr::include_graphics() bug, since that's how reticulate includes python plots, and is a difference between the Python MRE and the R examples in rstudio/rmarkdown#2525 (comment)

[t-kalinowski]

cc @cderv