feat: Use stable leaflet.providers html dep if available

[gadenbuie]

Fixes #732
Fixes #843
Closes #803
For rstudio/leaflet.providers#34

This PR pairs with rstudio/leaflet.providers#36 to use the html dependency created by leaflet.providers, if available.

With the latest version of leaflet.providers, leaflet will use a stable html dependency that will not change between R sessions and will, in general, be consistent in the knitr cache (excepting package updates which should break the cache anyway).

In the presence of an older version of leaflet.providers, leaflet will still create a temporary html dependency, so this is a backwards-compatible change.

With rstudio/leaflet.providers#36 loaded, you'll see:

leaflet()  |>
  setView(lng = -71.0589, lat = 42.3601, zoom = 12) |> 
  addTiles() |> 
  addProviderTiles("Stamen.Toner") |> 
  htmltools::findDependencies() |>
  purrr::keep(\(x) x$name == "leaflet-providers")
#> [[1]]
#> List of 10
#>  $ name      : chr "leaflet-providers"
#>  $ version   : chr "2.0.0"
#>  $ src       :List of 1
#>   ..$ file: chr "/Users/garrick/work/rstudio/leaflet.providers/inst"
#>  $ meta      : NULL
#>  $ script    : chr "leaflet-providers_2.0.0.js"
#>  $ stylesheet: NULL
#>  $ head      : NULL
#>  $ attachment: NULL
#>  $ package   : NULL
#>  $ all_files : logi FALSE
#>  - attr(*, "class")= chr "html_dependency"

And for versions other than the bundled leaflet-providers:

use_providers(get_providers("1.13.0"))

leaflet()  |>
  setView(lng = -71.0589, lat = 42.3601, zoom = 12) |> 
  addTiles() |> 
  addProviderTiles("Stamen.Toner") |> 
  htmltools::findDependencies() |>
  purrr::keep(\(x) x$name == "leaflet-providers")
#> [[1]]
#> List of 10
#>  $ name      : chr "leaflet-providers"
#>  $ version   : chr "1.13.0"
#>  $ src       :List of 1
#>   ..$ href: chr "https://unpkg.com/[email protected]"
#>  $ meta      : NULL
#>  $ script    : chr "leaflet-providers.js"
#>  $ stylesheet: NULL
#>  $ head      : NULL
#>  $ attachment: NULL
#>  $ package   : NULL
#>  $ all_files : logi FALSE
#>  - attr(*, "class")= chr "html_dependency"

[jaredlander]

Looks like this is a better version of #803. I was just coming across this problem yet again, so I'm glad it's being fixed.

[gadenbuie]

@jaredlander Ah sorry, I didn't realize there was prior work on this, I kinda just dropped in without a ton of context. Thanks for your previous PR and the interim fix! Barret and I did discuss doing something similar to what you proposed (picking a stable place to put the dependency file), but I think this approach will end up being a little easier to work with in the long run. End users won't have to think about any intermediate files and knitr/quarto caching should just work ™^🤞.

If you're running into this now and have the ability to test this PR with rstudio/leaflet.providers#36, I'd love to hear if that works for you. You can install from both PRs with something like this:

remote::install_github(c("rstudio/leaflet#884", "rstudio/leaflet.providers#36"))

[jaredlander]

@gadenbuie I'm just happy for whatever makes it work.

I'll try the PR versions soon hopefully. Right now I'm fighting an uphill battle trying to use {webshot} to take screenshots of maps made with {leafgl} (it won't: wch/webshot#45). And no, {webshot2} isn't ideal because I'm running this on a server and want to avoid installing Chrome.

[gadenbuie]

@schloerke The failure here is related to terra's use of inline functions (\(x)), which should be fixed in the next version of terra (I submitted a PR back on 9/7). Anyway, we can move forward here.

[schloerke]

Thank you!

[schloerke]

@jaredlander

And no, {webshot2} isn't ideal because I'm running this on a server and want to avoid installing Chrome.

If you any browser that will follow the chrome devtools protocol, you may use it. Example of using Brave browser for the default {chromote} browser: rstudio/shinytest2#330 (comment)

I hope you find a path forward with your WebGL screenshots.

[jaredlander]

If there was a completely headless server (with no GUI), I'd be more inclined to install that. Do you know any?