Can Quarto handle external assets (e.g. for HTML widgets) delivered over CDN?

[walkerke]

Description

I'm developing a package called mapgl, installable at remotes::install_github("walkerke/mapgl"). For licensing reasons, I'm bringing in the Mapbox GL JS JavaScript and CSS assets in via CDN rather than bundling them within the package. However, this gives Quarto problems:

---
title: "quarto_test"
format: html
editor: visual
---

```{r}
library(mapgl)

mapboxgl()
```

Gives:

Error in FUN(X[[i]], ...) : 
  Dependency mapbox-gl-js 3.4.0 is not disk-based
Calls: .main ... dependencies_from_render -> html_dependencies_as_string -> lapply -> FUN
Execution halted

I know this isn't a problem with my package per se, as disk-based assets render fine in Quarto. However - I do notice that R Markdown does not have the same problem (see my package documentation here, which I built in R Markdown for that reason).

Is there any workaround you know of to be able to pull in external assets via CDN? Or, does this merit filing an issue?

[mcanouil]

The error does not come from Quarto. It's from htmltools::copyDependencyToDir.

This function is used inside Quarto using the default, which is mustWork = TRUE.

If TRUE and dependency does not point to a directory on disk (but rather a URL location), an error is raised. If FALSE then non-disk dependencies are returned without modification.

• quarto-cli/src/resources/rmd/execute.R

  Lines 498 to 513 in 7de4253

  	# return the html dependencies as an HTML string suitable for inclusion
  	# in the head of a document
  	html_dependencies_as_string <- function(dependencies, files_dir) {
  	if (!rmarkdown:::dir_exists(files_dir)) {
  	dir.create(files_dir, showWarnings = FALSE, recursive = TRUE)
  	}
  	dependencies <- lapply(dependencies, htmltools::copyDependencyToDir, files_dir)
  	dependencies <- lapply(dependencies, function(dependency) {
  	dir <- dependency$src$file
  	if (!is.null(dir)) {
  	dependency$src$file <- gsub("\\\\", "/", paste(files_dir, basename(dir), sep = "/"))
  	}
  	dependency
  	})
  	return(htmltools::renderDependencies(dependencies, "file", encodeFunc = identity))
  	}

So right now, Quarto does not allow dependencies to be URL.

It's possible to change this behaviour, but it's not simply changing mustWork = TRUE to mustWork = FALSE.

CC. @cderv

[cderv]

We do use mustWork = FALSE in rmarkdown context
https://github.com/cderv/rmarkdown/blob/d0088950258f3835a9de9bafa0cb470e4040e3a9/R/html_dependencies.R#L316-L324

So right now, Quarto does not allow dependencies to be URL.

I don't know if this is by design or an oversight. I need to try some things with the feature we have. Usually we expect htmlDependency to provide on-disk version.

Thanks for the report.

[cderv]

I have opened an issue to track

• Support for online htmlDependency()  #10339

[walkerke]

Thank you @cderv and @mcanouil!

Just a thought as well - I'm noticing that there are issues rendering HTML widgets over in Positron (posit-dev/positron#2023) and I wonder if there is some relationship there (based on the discussion in posit-dev/positron#1742).

Perhaps of interest to @juliasilge @jmcphers - I have the exact same behavior in Positron (Mapbox won't render, but MapLibre does, and I bundle the MapLibre assets).

[jmcphers]

Positron's web views for interactive content (inherited from Code OSS) have pretty restrictive security settings and will only load content from allowlisted domains. If you open the Developer Tools (Toggle Developer Tools on the Command Palette), then switch to the Network tab in the tools, then try to render your widget, you can see there if requests to the CDN are being blocked (my guess is they are).

[mcanouil]

• Support for online htmlDependency()  #10339

[walkerke]

@jmcphers just as a heads up - this issue in Positron is now solved with the latest release! Thank you so much!

[jmcphers]

great, glad to hear it!