Consider moving yaml package from Suggests to Imports to avoid issues trying to use _brand.yml in non-interactive R sessions

[adam-gruer]

Describe the problem

_brand.yml not being read if the yaml package is not installed .
The developer gets no notification why it is not being read if:

• they are using the default arguments for bs_theme() AND
• R is being run in a non-interactive session such as a docker container with a CMD instruction such as:

CMD ["R", "-e", "options(shiny.autoload.r = TRUE)" ,"-e", "shiny::runApp( port = 3838, host = '0.0.0.0')"]

The cause is not easily identifiable if the shiny app is being run from an R session where interactive() is FALSE such as a docker container.

In interactive sessions when read_brand_yaml() is eventually called from the exported function bs_theme , the call to rlang::check_installed("yaml") prompts the user to install the missing package.

In non-interactive sessions the call to rlang::check_installed("yaml") returns an error.
This error gets caught by a trycatch in brand_resolve.NULL and the calling bs_theme() function replaces the null brand with bootstrap defaults.

it was really difficult to figure out why my brand settings weren't appearing in the container version of the app compared to local development until i realised that the container version only had shiny, bslib and the packages listed in their Imports installed.

Is it possible:

• to add the yaml package to bslib's Imports instead of Suggests and not rely on rlang::check_installed()? OR
• add some documentation for developers to recommend they install yaml when they want to use _brand.yml and their app or dashboard is not going to be run in interactive sessions?

Thanks for reading, I hope I have been able to describe with enough clarity.

reprex1 -
calling bs_theme(brand = NULL) from a non-interactive session returns default bundle etc but not the settings in _brand.yml supplied by the developer

root@4cfca3da1d1a:/app# R -e "rlang::is_installed('yaml')" -e "bslib::bs_theme(brand = NULL)" -e "bslib::bs_theme(brand = NULL) |> attr('brand') |> getElement('path')"

R version 4.5.0 (2025-04-11) -- "How About a Twenty-Six"
...
> rlang::is_installed('yaml')
[1] FALSE
> bslib::bs_theme(brand = NULL)
/* Sass Bundle: _utilities, _root, _reboot, _type, _images, _containers, _grid, _tables, _forms, _buttons, _transitions, _dropdown, _button-group, _nav, _navbar, _card, _accordion, _breadcrumb, _pagination, _badge, _alert, _progress, _list-group, _close, _toasts, _modal, _tooltip, _popover, _carousel, _spinners, _offcanvas, _placeholders, _helpers, _api, bs3compat, builtin */
@import "/usr/local/lib/R/site-library/bslib/lib/bs5/scss/_functions.scss";
@import "/usr/local/lib/R/site-library/bslib/bslib-scss/functions.scss";
...
$bslib-preset-type: builtin;
$bslib-preset-name: shiny;
$web-font-path: "font.css" !default;
...
> bslib::bs_theme(brand = NULL) |> attr('brand') |> getElement('path')
NULL

reprex 2 calling bs_theme(brand = TRUE) from a non-interactive session returns an error

root@4cfca3da1d1a:/app# R -e "rlang::is_installed('yaml')" -e "bslib::bs_theme(brand = TRUE)"

R version 4.5.0 (2025-04-11) -- "How About a Twenty-Six"
...
> rlang::is_installed('yaml')
[1] FALSE
> bslib::bs_theme(brand = TRUE)
Error in read_brand_yml(NULL) : The package "yaml" is required.
Calls: <Anonymous> ... brand_resolve.logical -> read_brand_yml -> <Anonymous>
Execution halted

reprex 3 calling calling bs_theme(brand = NULL) from a non-interactive session when the yaml package IS installed

root@4cfca3da1d1a:/app# R -e "rlang::is_installed('yaml')" -e "bslib::bs_theme(brand = NULL) |> attr('brand') |> getElement('path')"

R version 4.5.0 (2025-04-11) -- "How About a Twenty-Six"
...
> rlang::is_installed('yaml')
[1] TRUE
> bslib::bs_theme(brand = NULL) |> attr('brand') |> getElement('path')
[1] "/app/_brand.yml"

Session Info

─ Session info ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.5.0 (2025-04-11)
 os       Ubuntu 22.04.1 LTS
 system   x86_64, linux-gnu
 ui       X11
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       UTC
 date     2025-04-22
 pandoc   NA
 quarto   NA
─ Packages ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────

package     * version date (UTC) lib source

bspm          0.5.7          [2] local

cachem        1.1.0   2024-05-16 [2] RSPM (R 4.4.0)

cli           3.6.4   2025-02-13 [2] RSPM (R 4.4.0)

devtools      2.4.5   2022-10-11 [2] RSPM (R 4.2.0)

digest        0.6.37  2024-08-19 [2] RSPM (R 4.4.0)

ellipsis      0.3.2   2021-04-29 [2] RSPM (R 4.2.0)

fastmap       1.2.0   2024-05-15 [2] RSPM (R 4.4.0)

fs            1.6.6   2025-04-12 [2] RSPM (R 4.4.0)

glue          1.8.0   2024-09-30 [2] RSPM (R 4.4.0)

htmltools     0.5.8.1 2024-04-04 [2] RSPM (R 4.3.0)

htmlwidgets   1.6.4   2023-12-06 [2] RSPM (R 4.3.0)

httpuv        1.6.16  2025-04-16 [2] RSPM (R 4.4.0)

later         1.4.2   2025-04-08 [2] RSPM (R 4.4.0)

lifecycle     1.0.4   2023-11-07 [2] RSPM (R 4.3.0)

magrittr      2.0.3   2022-03-30 [2] RSPM (R 4.2.0)

memoise       2.0.1   2021-11-26 [2] RSPM (R 4.2.0)

mime          0.13    2025-03-17 [2] RSPM (R 4.4.0)

miniUI        0.1.2   2025-04-17 [2] RSPM (R 4.4.0)

pkgbuild      1.4.7   2025-03-24 [2] RSPM (R 4.4.0)

pkgload       1.4.0   2024-06-28 [2] RSPM (R 4.4.0)

profvis       0.4.0   2024-09-20 [2] RSPM (R 4.4.0)

promises      1.3.2   2024-11-28 [2] RSPM (R 4.4.0)

purrr         1.0.4   2025-02-05 [2] RSPM (R 4.4.0)

R6            2.6.1   2025-02-15 [2] RSPM (R 4.4.0)

Rcpp          1.0.14  2025-01-12 [2] RSPM (R 4.4.0)

remotes       2.5.0   2024-03-17 [2] RSPM (R 4.3.0)

rlang         1.1.6   2025-04-11 [2] RSPM (R 4.4.0)

sessioninfo   1.2.3   2025-02-05 [2] RSPM (R 4.4.0)

shiny         1.10.0  2024-12-14 [2] RSPM (R 4.4.0)

urlchecker    1.0.1   2021-11-30 [2] RSPM (R 4.2.0)

usethis       3.1.0   2024-11-26 [2] RSPM (R 4.4.0)

vctrs         0.6.5   2023-12-01 [2] RSPM (R 4.3.0)

xtable        1.8-4   2019-04-21 [2] RSPM (R 4.2.0)
[1] /usr/local/lib/R/site-library

[2] /usr/lib/R/site-library

[3] /usr/lib/R/library

[gadenbuie]

Thanks for opening the issue, that does sound frustratingly hard to diagnose. I'm working on a brand.yml R package right now and will make sure this is addressed when I fold that package into bslib.

For now I would recommend use brand = TRUE or giving a path to the _brand.yml file when you're deploying to production.

For my own notes, the problematic error-catching happens here:

bslib/R/bs-theme-preset-brand.R

Lines 92 to 98 in 7cf8050

	brand <- tryCatch(
	read_brand_yml(NULL),
	error = function(err) {
	# Couldn't find _brand.yml but we're not going to error
	NULL
	}
	)

I was intending to catch the read_brand_yml() error but unintentionally swallowing the check_installed() error. I think the fix will be two-fold:

1. Throw a classed brand_yml_not_found error and ignore that specifically in the above tryCatch() (as intended).
2. Emit warnings for other errors

[adam-gruer]

Thank you Garrick for the quick response, and thanks for this great package.
I will implement your recommendation for deploying to production.