How do I force saveWidget to create a single file outside of RStudio?

Question

In RStudio I can save my html widget to a single file with:

htmlwidgets::saveWidget(x,"filename.html",selfcontained=TRUE)

When running an R script with the above line through windows Task Scheduler (which calls Rscript.exe) this would generate a multi-file html (i.e. an html file with an associated directory of referenced stuff). Using RGui also failed to generate a single-file html.
These are the lines from an Rgui implementation that replicates the issue:

> library(leaflet)
> library(htmlwidgets)
> map <- leaflet::leaflet() %>% addTiles() %>% setView(lng=172.4,lat=-41,zoom=6)
> saveWidget(map,file="deleteme.html",selfcontained=TRUE)
Error in saveWidget(map, file = "deleteme.html", selfcontained = TRUE) : 
  Saving a widget with selfcontained = TRUE requires pandoc. For details see:
https://github.com/rstudio/rmarkdown/blob/master/PANDOC.md
> list.files(getwd(),full.names=FALSE, recursive=TRUE)
 [1] "deleteme.html"                                           
 [2] "deleteme_files/htmlwidgets-1.5.3/htmlwidgets.js"         
 [3] "deleteme_files/jquery-1.12.4/jquery.min.js"              
 [4] "deleteme_files/leaflet-1.3.1/images/layers-2x.png"       
 [5] "deleteme_files/leaflet-1.3.1/images/layers.png"          
 [6] "deleteme_files/leaflet-1.3.1/images/marker-icon-2x.png"  
 [7] "deleteme_files/leaflet-1.3.1/images/marker-icon.png"     
 [8] "deleteme_files/leaflet-1.3.1/images/marker-shadow.png"   
 [9] "deleteme_files/leaflet-1.3.1/leaflet.css"                
[10] "deleteme_files/leaflet-1.3.1/leaflet.js"                 
[11] "deleteme_files/leaflet-binding-2.0.4.1/leaflet.js"       
[12] "deleteme_files/leafletfix-1.0.0/leafletfix.css"          
[13] "deleteme_files/proj4-2.6.2/proj4.min.js"                 
[14] "deleteme_files/Proj4Leaflet-1.0.1/proj4leaflet.js"       
[15] "deleteme_files/rstudio_leaflet-1.3.1/images/1px.png"     
[16] "deleteme_files/rstudio_leaflet-1.3.1/rstudio_leaflet.css"

A clue to the cause is the error message returned after running the saveWidget function (though the web link provided no longer works). The error message points out that htmlwidgets::saveWidget function requires pandoc.exe application to be available for it to create a single-file html. If it is not available then it creates a multi-file html.

But I have pandoc.exe installed, as it comes with the RStudio bundle, which I use all the time.

As it turns out, the availability of pandoc.exe is checked by htmlwidgets::saveWidget using the rmarkdown::find_pandoc function. This checks for the existence of pandoc.exe in paths saved in the "RSTUDIO_PANDOC" and "PATH" environment variables and in the ~/opt/pandoc/ directory.
When using RStudio, the "RSTUDIO_PANDOC" environment variable is automagically set. It is not set when I run a script via Task Scheduler as, in that case I use Rscript.exe. When pandoc.exe is installed (it comes in the RStudio bundle) the PATH environment variable is not set so it can't be found that way either.

So how do I get saveWidget to save to a single html file when I'm not using RStudio?

score 2 · Answer 1 · edited May 25 '21 at 22:12

One solution is to explicitly set the RSTUDIO_PANDOC environment variable. Alternatively pandoc.exe could be added to the PATH environment variable. Either of the above could be added to the .Renviron file. Here is an example of the first approach:

> library(leaflet)
> library(htmlwidgets)
> map <- leaflet::leaflet() %>% addTiles() %>% setView(lng=172.4,lat=-41,zoom=6)
> Sys.setenv(RSTUDIO_PANDOC = "C:/Program Files/RStudio/bin/pandoc")
> saveWidget(map,file="deleteme.html",selfcontained=TRUE)
> list.files(getwd(),full.names=FALSE, recursive=TRUE)
[1] "deleteme.html"

How do I force saveWidget to create a single file outside of RStudio?

1 Answers1