rstudio / rstudio/bslib

The two <body> problem

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Description

Describe the problem

When creating a multi-page Shiny application with page_navbar(), it seems that two <body> tags are generated.

This can be reproduced from the page_navbar() help page example:

library(shiny)
library(bslib)

link_shiny <- tags$a(
  shiny::icon("github"), "Shiny",
  href = "https://github.com/rstudio/shiny",
  target = "_blank"
)
link_posit <- tags$a(
  shiny::icon("r-project"), "Posit",
  href = "https://posit.co",
  target = "_blank"
)

ui <- page_navbar(
  title = "My App",
  nav_panel(title = "One", p("First page content.")),
  nav_panel(title = "Two", p("Second page content.")),
  nav_panel("Three", p("Third page content.")),
  nav_spacer(),
  nav_menu(
    title = "Links",
    align = "right",
    nav_item(link_shiny),
    nav_item(link_posit)
  )
)

server <- function(...) { } # not used in this example

shinyApp(ui, server)

The source code (as displayed by Firefox 138.0.3 on Ubuntu 24.04) presents two nested <body> tags:

<!DOCTYPE html>
<html>
<head>
...
</head>
<body>
  <body class="bslib-page-fill bslib-gap-spacing bslib-flow-mobile html-fill-container bslib-page-navbar" style="padding:0px;gap:0px;">
  ...
  </body>
</body>
</html>

Am I missing something?

Session Info

> devtools::session_info()
─ Session info ─
 setting  value
 version  R version 4.5.0 (2025-04-11)
 os       Ubuntu 24.04.2 LTS
 system   x86_64, linux-gnu
 ui       RStudio
 language fr_FR:en_US:en
 collate  fr_FR.UTF-8
 ctype    fr_FR.UTF-8
 tz       Europe/Paris
 date     2025-06-06
 rstudio  2025.05.0+496 Mariposa Orchid (desktop)
 pandoc   3.1.3 @ /usr/bin/pandoc
 quarto   1.6.42 @ /usr/lib/rstudio/resources/app/bin/quarto/bin/quarto

─ Packages ─

package     * version    date (UTC) lib source

bslib       * 0.9.0.9000 2025-06-06 [1] Github (rstudio/bslib@7cf8050)

cachem        1.1.0      2024-05-16 [1] CRAN (R 4.5.0)

cli           3.6.5      2025-04-23 [1] CRAN (R 4.5.0)

devtools      2.4.5      2022-10-11 [1] CRAN (R 4.5.0)

digest        0.6.37     2024-08-19 [1] CRAN (R 4.5.0)

ellipsis      0.3.2      2021-04-29 [1] CRAN (R 4.5.0)

fastmap       1.2.0      2024-05-15 [1] CRAN (R 4.5.0)

fontawesome   0.5.3      2024-11-16 [1] CRAN (R 4.5.0)

fs            1.6.6      2025-04-12 [1] CRAN (R 4.5.0)

glue          1.8.0      2024-09-30 [1] CRAN (R 4.5.0)

htmltools     0.5.8.1    2024-04-04 [1] CRAN (R 4.5.0)

htmlwidgets   1.6.4      2023-12-06 [1] CRAN (R 4.5.0)

httpuv        1.6.16     2025-04-16 [1] CRAN (R 4.5.0)

jquerylib     0.1.4      2021-04-26 [1] CRAN (R 4.5.0)

jsonlite      2.0.0      2025-03-27 [1] CRAN (R 4.5.0)

later         1.4.2      2025-04-08 [1] CRAN (R 4.5.0)

lifecycle     1.0.4      2023-11-07 [1] CRAN (R 4.5.0)

magrittr      2.0.3      2022-03-30 [1] CRAN (R 4.5.0)

memoise       2.0.1      2021-11-26 [1] CRAN (R 4.5.0)

mime          0.13       2025-03-17 [1] CRAN (R 4.5.0)

miniUI        0.1.2      2025-04-17 [1] CRAN (R 4.5.0)

pillar        1.10.2     2025-04-05 [1] CRAN (R 4.5.0)

pkgbuild      1.4.8      2025-05-26 [1] CRAN (R 4.5.0)

pkgconfig     2.0.3      2019-09-22 [1] CRAN (R 4.5.0)

pkgload       1.4.0      2024-06-28 [1] CRAN (R 4.5.0)

profvis       0.4.0      2024-09-20 [1] CRAN (R 4.5.0)

promises      1.3.3      2025-05-29 [1] CRAN (R 4.5.0)

purrr         1.0.4      2025-02-05 [1] CRAN (R 4.5.0)

R6            2.6.1      2025-02-15 [1] CRAN (R 4.5.0)

Rcpp          1.0.14     2025-01-12 [1] CRAN (R 4.5.0)

remotes       2.5.0      2024-03-17 [1] CRAN (R 4.5.0)

rlang         1.1.6      2025-04-11 [1] CRAN (R 4.5.0)

rstudioapi    0.17.1     2024-10-22 [1] CRAN (R 4.5.0)

sass          0.4.10     2025-04-11 [1] CRAN (R 4.5.0)

sessioninfo   1.2.3      2025-02-05 [1] CRAN (R 4.5.0)

shiny       * 1.10.0     2024-12-14 [1] CRAN (R 4.5.0)

tibble        3.2.1      2023-03-20 [1] CRAN (R 4.5.0)

urlchecker    1.0.1      2021-11-30 [1] CRAN (R 4.5.0)

usethis       3.1.0      2024-11-26 [1] CRAN (R 4.5.0)

vctrs         0.6.5      2023-12-01 [1] CRAN (R 4.5.0)

xtable        1.8-4      2019-04-21 [1] CRAN (R 4.5.0)


[1] xxx

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

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

[4] /usr/lib/R/library


    

  • ── Packages attached to the search path. here

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the page_navbar() help example using the supplied R session and inspect the generated HTML in Firefox to trace the two body elements. Done means the example renders with a single valid body element and the behavior is covered by an appropriate regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
r
Domain
frontend, web-dev
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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