Extrernal resource cannot be found without `addResourcePath()` although it's part of www\

[FBrockmeyer]

System Details

Tried different browsers.

> sessionInfo()
R version 4.5.2 (2025-10-31)
Platform: x86_64-pc-linux-gnu
Running under: Ubuntu 24.04.4 LTS

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 
LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.26.so;  LAPACK version 3.12.0

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

time zone: Etc/UTC
tzcode source: system (glibc)

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

other attached packages:
[1] shiny_1.13.0

loaded via a namespace (and not attached):
 [1] igraph_2.2.2      digest_0.6.39     later_1.4.7       R6_2.6.1         
 [5] httpuv_1.6.16     fastmap_1.2.0     magrittr_2.0.4    cachem_1.1.0     
 [9] pkgconfig_2.0.3   htmltools_0.5.9   lifecycle_1.0.5   promises_1.5.0   
[13] cli_3.6.5         xtable_1.8-8      visNetwork_2.1.4  compiler_4.5.2   
[17] rstudioapi_0.18.0 tools_4.5.2       mime_0.13         Rcpp_1.1.1       
[21] otel_0.2.0        jsonlite_2.0.0    htmlwidgets_1.6.4 rlang_1.1.7      
[25] box_1.2.1     

Project's Structure

project/
|-- notebooks/
    |-- .... 
|   `-- README.Rmd
|-- www/
|   |-- logo.png
|   |-- header.html
|   `-- styles.css
|-- shiny/
    |-- R/
        |-- server.R
        |-- ui.R
        `-- mods/ 
    `-- library/
|-- app.R
`-- README.md 

File Details

header.html looks like

<header>
  <h1 class="header-title">blah</h1>
  <img src=www/logo.png alt="blah-Logo" class="header-logo">
</header>

while ui.R is similar to

# Module Management -------------------------------------------------------
box::use(
  shiny[fluidPage, includeHTML, includeCSS, addResourcePath, tags], # not adapted
  <...>
  )

# User Interface ----------------------------------------------------------------
#' @export
ui = function() {
  fluidPage(
    title = 'blah',
    # shiny deploys from app.R root (project)
    includeHTML('www/header.html'), 
   <...>
   )
}

and app.R is somewhat irregular

# Module Management ----------------------------------------------------
box::use(
  shiny[shinyApp, runApp],
  ./shiny/R/server, 
  ./shiny/R/ui
  ) 


# ENTRYPOINT --------------------------------------------------------------
shinyApp(
  ui = ui$ui,
  server = server$server,
  options = list(
      <...> 
    )
  ) |> 
  runApp()

Problem Detail

When running the app, www/logo.png in www/header.html cannot be found. This doesn't change when deleting the www/-prefix. However, when adding addResourcePath(prefix = 'www', directoryPath = './www') above ui() in ui.R the logo gets displayed as expected (as long as the prefix is set). I do not understand where this is in line with addResourcePath() documentation. Same holds for the styles.css.

[ismirsehregal]

The default resource publishing via the www folder is using / as its prefix not www.

In your app.R file you are passing a shiny app object to runApp(), accordingly the www folder is not considered. Please see this related SO post.

And I think you should either use the two-file (server.R and ui.R + global.R) or the single-file (app.R) approach not both.

[FBrockmeyer]

@ismirsehregal, thanks for pointing to that; it's poor documentation then.
Also, thanks for the note about file management. We are asked to use the structure as given (i.e. www/, shiny/, app.R in root directory) + {box} and do not see how to adapt to one of those.

[ismirsehregal]

I'm not familiar with {box}, however, to create a standard-compliant shiny application app.R must return an object created by the shinyApp() function.

So if you would like to make use of the www folder you'll need to get rid of the runApp() call in app.R.

[FBrockmeyer]

Thanks, again, @ismirsehregal Interesting. It is there for convenience in developement (interactive use), allowing the use of RStudio's Run App Button.

Edit: To me it seems like even after removing runApp() addResourcePath() is still needed.

[ismirsehregal]

RStudio's "Run App" Button will be available nonetheless and printing a shiny app object will also run it (ctrl+Enter shinyApp() in RStudio).