cols_width() Produces an Error When Using pct() inside It in LaTeX/PDF Output

[briandk]

The Problem

If a user specifies a cols_width() value using the pct() function and tries to render to PDF, the render will fail with an error at the LaTeX compile stage (exact line number of the error depends on document content):

compilation failed- error
Paragraph ended before \scr@LT@array was complete.
<to be read again> 
                   \par 
l.195 

Expected Behavior

Using a pct() call to specify column widths with cols_width() when outputting to LaTeX/PDF should not produce an error.

Actual Behavior

The resulting knitted document produces an error at the LaTeX compilation stage.

Minimal Reproducible R Script

Compiling this script as its own file should produce the LaTeX error.
Also, by preserving LaTeX output we can visually inspect the generated LaTeX.

#' ---
#' output:
#'   pdf_document:
#'     keep_md: true
#'     keep_tex: true
#'
#' ---

library(gt)
library(sessioninfo)

mtcars |> gt() |>
  cols_width(everything() ~ pct(15)) # an arbitrary column width for example purposes
session_info()

The Offending LaTeX Lines

\begin{longtable}{>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}>{\raggedleft\arraybackslash}p{15%}}

We can see from the LaTeX above that the % is causing all characters following it to be treated as a comment, rather than executable LaTeX.

Tracing the Problem through gt

1. When a user specifies a percentage with pct() inside a cols_width() call, the pct() call just takes that number and converts it into a string by concatenating a raw % to the number.
2. That string value---which includes the raw % sign, gets passed to create_table_start_l(). On line 175 of that function, if the value of col_widths[i] isn't null, we eventually move to line 186, where col_widths[i] gets pasted in seemingly without any check as to whether it contains a raw % sign.
3. At this point col_widths[i] will necessarily contain the raw percent sign. So...
4. The resulting text: "p{", col_widths[i], "}" gets passed on to LaTeX, where the LaTeX compiler interprets anything following an unescaped % as a comment.
5. The call to p{} in LaTeX never gets a closing brace, because of the comment symbol.
6. LaTeX fails to compile the document.

A Temporary Work-Around

Instead of calling pct(), a user can specify a string literal with a backslash-escaped %, as in this fully reproducible script

#' ---
#' output:
#'   pdf_document:
#'     keep_md: true
#'     keep_tex: true
#'
#' ---

library(gt)

mtcars |> gt() |>
  cols_width(everything() ~ "15\\%")

Session Info

─ Session info ────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.3.1 (2023-06-16)
 os       macOS Ventura 13.5.2
 system   aarch64, darwin20
 ui       RStudio
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       America/New_York
 date     2023-10-06
 rstudio  2023.06.1+524 Mountain Hydrangea (desktop)
 pandoc   3.1.7 @ /opt/homebrew/bin/ (via rmarkdown)

─ Packages ────────────────────────────────────────────────────────────────────────────
 package     * version    date (UTC) lib source
 bit           4.0.5      2022-11-15 [1] CRAN (R 4.3.0)
 bit64         4.0.5      2020-08-30 [1] CRAN (R 4.3.0)
 cli           3.6.1      2023-03-23 [1] CRAN (R 4.3.0)
 crayon        1.5.2      2022-09-29 [1] CRAN (R 4.3.0)
 digest        0.6.33     2023-07-07 [1] CRAN (R 4.3.0)
 dplyr       * 1.1.3      2023-09-03 [1] CRAN (R 4.3.0)
 evaluate      0.22       2023-09-29 [1] CRAN (R 4.3.1)
 fansi         1.0.4      2023-01-22 [1] CRAN (R 4.3.0)
 fastmap       1.1.1      2023-02-24 [1] CRAN (R 4.3.0)
 generics      0.1.3      2022-07-05 [1] CRAN (R 4.3.0)
 glue          1.6.2      2022-02-24 [1] CRAN (R 4.3.0)
 gt          * 0.9.0.9000 2023-10-06 [1] Github (wildoane/gt@aee1944)
 here        * 1.0.1      2020-12-13 [1] CRAN (R 4.3.0)
 hms           1.1.3      2023-03-21 [1] CRAN (R 4.3.0)
 htmltools     0.5.6      2023-08-10 [1] CRAN (R 4.3.0)
 janitor     * 2.2.0      2023-02-02 [1] CRAN (R 4.3.0)
 knitr         1.44       2023-09-11 [1] CRAN (R 4.3.0)
 lifecycle     1.0.3      2022-10-07 [1] CRAN (R 4.3.0)
 lubridate     1.9.3      2023-09-27 [1] CRAN (R 4.3.1)
 magrittr    * 2.0.3      2022-03-30 [1] CRAN (R 4.3.0)
 pillar        1.9.0      2023-03-22 [1] CRAN (R 4.3.0)
 pkgconfig     2.0.3      2019-09-22 [1] CRAN (R 4.3.0)
 purrr         1.0.2      2023-08-10 [1] CRAN (R 4.3.0)
 R6            2.5.1      2021-08-19 [1] CRAN (R 4.3.0)
 readr       * 2.1.4      2023-02-10 [1] CRAN (R 4.3.0)
 rlang         1.1.1      2023-04-28 [1] CRAN (R 4.3.0)
 rmarkdown     2.25       2023-09-18 [1] CRAN (R 4.3.1)
 rprojroot     2.0.3      2022-04-02 [1] CRAN (R 4.3.0)
 rstudioapi    0.15.0     2023-07-07 [1] CRAN (R 4.3.0)
 sass          0.4.7      2023-07-15 [1] CRAN (R 4.3.0)
 sessioninfo * 1.2.2      2021-12-06 [1] CRAN (R 4.3.0)
 snakecase     0.11.1     2023-08-27 [1] CRAN (R 4.3.0)
 stringi       1.7.12     2023-01-11 [1] CRAN (R 4.3.0)
 stringr     * 1.5.0      2022-12-02 [1] CRAN (R 4.3.0)
 tibble      * 3.2.1      2023-03-20 [1] CRAN (R 4.3.0)
 tidyr       * 1.3.0      2023-01-24 [1] CRAN (R 4.3.0)
 tidyselect    1.2.0      2022-10-10 [1] CRAN (R 4.3.0)
 timechange    0.2.0      2023-01-11 [1] CRAN (R 4.3.0)
 tzdb          0.4.0      2023-05-12 [1] CRAN (R 4.3.0)
 utf8          1.2.3      2023-01-31 [1] CRAN (R 4.3.0)
 vctrs         0.6.3      2023-06-14 [1] CRAN (R 4.3.0)
 vroom         1.6.3      2023-04-28 [1] CRAN (R 4.3.0)
 withr         2.5.1      2023-09-26 [1] CRAN (R 4.3.1)
 xfun          0.40       2023-08-09 [1] CRAN (R 4.3.0)
 xml2          1.3.5      2023-07-06 [1] CRAN (R 4.3.0)
 yaml          2.3.7      2023-01-23 [1] CRAN (R 4.3.0)

 [1] /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/library

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[olivroy]

This is fixed with gt 0.11 as a result of #1495