src attribute overwritten, making iframe ineffective

[ijlyttle]

There is a problem with vembedr which I (think I) have traced back to here. This was first raised by @jnolis, in a tweet.

Here's my example Rmd:

---
title: "src gets rewritten"
output: html_document
---

```{r setup, include=FALSE}
library("htmltools")
```

```{r problem}
tags$iframe(src = "https://www.youtube.com/embed/uV4UpCq2azs")
```

In the past, the <iframe src> attribute would be written verbatim to the HTML file.

Currently, something happens to it, and it doesn't work:

My suspicion is that the change happened in #2151 (of course, I could be wrong).

I don't know enough about html-dependencies to be effective to diagnose further, but I stand ready to help.

Thanks!

R version 4.1.2 (2021-11-01)
Platform: x86_64-apple-darwin17.0 (64-bit)
Running under: macOS Big Sur 11.6.1, RStudio 2021.9.1.372

Locale: en_US.UTF-8 / en_US.UTF-8 / en_US.UTF-8 / C / en_US.UTF-8 / en_US.UTF-8

Package version:
  base64enc_0.1.3  bslib_0.3.1      digest_0.6.29    evaluate_0.14    fastmap_1.1.0    fs_1.5.1         glue_1.5.1       graphics_4.1.2  
  grDevices_4.1.2  highr_0.9        htmltools_0.5.2  jquerylib_0.1.4  jsonlite_1.7.2   knitr_1.36       magrittr_2.0.1   methods_4.1.2   
  R6_2.5.1         rappdirs_0.3.3   rlang_0.4.12     rmarkdown_2.11.3 sass_0.4.0       stats_4.1.2      stringi_1.7.6    stringr_1.4.0   
  tinytex_0.35     tools_4.1.2      utils_4.1.2      xfun_0.28        yaml_2.2.1      

Pandoc version: 2.14.0.3

---

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[jnolis]

As an additional datapoint, you don't even need the vembedr package to have issues with embedding YouTube. If you use the HTML code directly from YouTube in an RMarkdown file, it won't correctly show when you knit it. Try this example RMarkdown file, with an embeded YouTube video taken from right clicking on a video in YouTube and getting the embed code:

---
title: "test-youtube"
output: html_document
---

<iframe width="1280" height="720" src="https://www.youtube.com/embed/RndK5em1dHo" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

After you turn it into HTML, the iframe has the same issue as mentioned above. Not being able to have YouTube videos embedded in RMarkdown files seems like meaningful issue to me, as you might want to use videos as part of tutorials or lessons.

[atusy]

This behavior comes from html_document(self_contained = TRUE), which tries to include as much external sources as possible into a single html file.

You have two choices to workaround.

1. use self_contained = FALSE
2. use data-external = 1 attribute in html tags to let them be exceptions.

   tags$iframe(src = "https://www.youtube.com/embed/uV4UpCq2azs", `data-external` = 1)

[atusy]

Note that this is the feature of pandoc and is not a bug.

[cderv]

Thanks @atusy for the quick help and answer !

This is indeed something that comes from Pandoc since 2.11.2 I believe. Pandoc will now encode a wider range of component. You need to use data-external attributes explicitly on elements you don't want Pandoc to encode in a self-contained mode.

To simplify that, note that since knitr 1.34 knitr::include_url() adds the attributes data-external="1" to iframe so that one don't need to remember it or do it explicitly. If you write HTML code directly in R Markdown document, you need to add it yourself.

for vembedr, maybe knitr function could be used maybe to benefit from knit_print and sewing method in knitr.

If you're ok with it, maybe we could close this issue ?

[ijlyttle]

Thanks @cderv and @autsy!

Happy to close the issue, but may come back to ask for some clarifications, if needed.

[cderv]

Happy to close the issue, but may come back to ask for some clarifications, if needed.

Please do note hesitate. You can also ping me in any PR / issue in vembedr

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