unexpected behavior when table cell ends with a latex space "\ "

[mjsmith037]

Describe the bug

When a table cell ends with an explicit space, specified in latex as "\ ", kable inappropriately prunes the space, resulting in erroneous latex code that cannot be compiled.

To reproduce

library(knitr)
kable(data.frame(x="\\ "), format="latex", escape=FALSE)

produces:

\begin{tabular}{l}
\hline
x\\
\hline
\\\
\hline
\end{tabular}

Note that line 5 of the output should be "\ \\" (with a space between the first and second backslashes).

When attempting to compile this, an erroneous .pdf is produced:

test.pdf

Session info

xfun::session_info('knitr')

R version 4.3.0 (2023-04-21)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Linux Mint 20.3, RStudio 2023.9.0.463

Locale:
  LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
  LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8    LC_PAPER=en_US.UTF-8       LC_NAME=C                 
  LC_ADDRESS=C               LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

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

Package version:
  evaluate_0.21   graphics_4.3.0  grDevices_4.3.0 highr_0.10      knitr_1.43      methods_4.3.0   stats_4.3.0     tools_4.3.0    
  utils_4.3.0     xfun_0.39       yaml_2.3.7  

Note this issue was previously, erroneously posted in the kableExtra repo.

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[cderv]

Yes I believe we are trimming whitespace, no matter the escape settings... 🤔

https://github.com/yihui/knitr/blob/4b47d2a57bd6ac31712d0afafbc4fe968b663c92/R/table.R#L156

@yihui do you think we could have some specific handling in some case ? Either trimming when escape = TRUE only ?

with additional check on whitespace espace sequence depending on format ? 🤔

Or maybe we need a specific marked string to not trim....

Like

data.frame(x=I("\\ "))

[yihui]

Trailing spaces escaped by \ are no longer trimmed. Thanks!

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