Could anybody explain for what reason I have created the following filter?

[johnmapeson]

This is kinda a weird question.

In April I asked how to create a Lua filter to preserve videos if converting from HTML to GitHub Flavored Markdown. @jgm helped me, and here are a link: #9658 and code:

pandoc -f html+raw_html input.htm -t gfm-raw_html -o output.md --wrap=none --lua-filter preserve-videos.lua

local function starts_with(start, str)
  return str:sub(1, #start) == start
end

function RawBlock (el)
  return ((starts_with('<video', el.text)
      or starts_with('</video', el.text)
      or starts_with('<source', el.text))
      and pandoc.RawBlock('markdown', el.text))
      or {}
end

But what I don't understand now is that for what reason I have created this filter. Isn't it

pandoc -f html+raw_html input.htm -t gfm-raw_html -o output.md --wrap=none

preserves videos even without it?

I suspect the filter does have its use, but I forgot the use that does make sense for it. Any help is much appreciated!

[alerque]

Given that your original example is not currently reproducible (I just used Pandoc 3.3 to run your input and command and got a different result) I would guess the answer is that something got fixed/changed in the mean time and the need for the filter is obsolete.

[johnmapeson]

Hello, Caleb. I cannot test it with Pandoc 3.3, but I have just updated Pandoc to 2.3.1 by using brew upgrade, and here is how it works for me:

input.htm:

<!-- comment -->
<h1>heading</h1>
<p>body</p>
<img src="image.png"</img>
<p>body</p>
<video controls><source src="video.mp4"></video>
<p>body</p>

Then, either...

• pandoc -f html+raw_html input.htm -t gfm-raw_html -o output.md --lua-filter preserve-videos.lua
• pandoc -f html+raw_html input.htm -t gfm-raw_html -o output.md

produces the same output.md:

# heading

body

![](image.png)

body

<video controls>

<source src="video.mp4">

</video>

body

The output files are the same and the video is preserved even without a filter.