How to append content of a .qmd file to the one currently rendered using a lua fragment?

[alesvomacka]

Description

Hi,
I'm trying to create a simple lua script that would to append content of one .qmd to another. The goal is to automatically append a slide containing contact info at the end of my presentations without having to do so manually.

Currently, the script looks like this:

-- End slide content
local end_slide = io.open("ending.qmd", "r")
local end_content = end_slide:read("*all")
end_slide:close()

-- Append to the rest of the slides
local main_slides = io.open("template.qmd", "a")
main_slides:write(end_content)
main_slides:close()

Is there a way to refer to the currently rendered file, instead of hardcoding its name into the script (e.g. "template.qmd")? Ideally, I would like to call the lua script as a fragment in the YAML. Thanks a lot!

[baptiste]

I'm not sure this is the right approach: Lua filters are called relatively late in the rendering process, after Quarto has already processed the qmd files and pandoc has parsed the results into an abstract syntax tree. (Pandoc Lua readers act earlier than that, but I doubt they're relevant here). So in that sense, it seems too late to include a qmd file at this stage.

It sounds like you could use quarto includes instead? Or perhaps adjust the document template, if using latex/html/typst/etc formats.

[alesvomacka]

Thanks. I have thought about the include shortcode, but I couldn't think of a way to use it without me having to manually adding it to the document.

By adjusting template, you mean adjusting the (for example) reveal.js template itself? If so, could you point me to a document that describes the process? I'm not familiar with javascript to know where to start.

[baptiste]

You should share a minimal reproducible example of what you're trying to do (main slides and document to insert), but also take a look at these templates:

https://quarto.org/docs/journals/templates.html#revealjs-partials

You could copy the template file and add your custom slide after $body$, or something similar.

[cderv]

You could also consider Quarto Project, and using a pre-render script (About Project Script. You could add your content using a script to all the other .qmd that requires it before Quarto does its processing

It sounds like you could use quarto includes instead?

Using includes shortcode is really just one line, and this is the best way to add the content of a .qmd to another .qmd and have the merged document process as a single .qmd

Using Lua, you could just consider the Doc block, and add your parsed ending.qmd to it (See pandoc.read()). This will add content to the already parsed AST, so you don't need the document name. However, this will work more with ending.md than a ending.qmd (as the content should be only Pandoc processed content - no code chunk, or complex Quarto representation).

You could copy the template file and add your custom slide after $body$, or something similar.

If the aim is to add some content after body, then using the Pandoc includes features is probably easier than modifying template
https://quarto.org/docs/output-formats/html-basics.html#includes

Hope it helps

[cl-roberts]

Hi there,

I made a filter called append-qmd that I believe does what you're after. Simply acquire that repository and add your contact info to a .qmd file; place it in the same directory as the .lua script.

Also, pandoc has a filter called include-files that is a little more flexible but is less automated. You have to write a code block with class .include in the body of your main document to prompt inclusion of external markdown files .

[cl-roberts]

I agree that an include shortcode is a better approach in most cases. In my particular use case, I have a handful of related documents in different formats within a project and wanted to add generic appendices to all using a shared YAML, so I think this approach makes sense. I could also envision a scenario where you need to append many files with a shell script, and adding a line to the YAML is easier then adding shortcode.

[cderv]

@clroberts-adfg Nice filter!
does your filter works with any content in the .qmd ? Which format are you reading ? I see pandoc.read(..., nil) - what is nil referring to as reading format ?

@cscheid this type of filter is using pandoc.read(). I believe in Quarto we are using a specific .qmd reader for .qmd file. Could there be some side effect, like feature not working if the filter is just using pandoc.read() without using this specific reader ?

Overall, using external Lua filter for that seems an approach that would work for .md file mainly, without any .qmd specific content.
I wonder if there should be a quarto.read() exported in our Quarto API. Maybe too complex though...

[cscheid]

@cderv You're correct, if the code uses pandoc.read(), then (for example), triple-trick code syntax is unlikely to work, as are shortcodes. You are also correct that we need a quarto.read() API or something like that. But we don't have it yet.

[cderv]

Thanks for confirming !

[cl-roberts]

@cderv That's a good point, this is really appending .qmd files with .md files since .qmd content can't be read as far as I know. The nil in pandoc.read just specifies the default format value (which is markdown); I changed it to be more explicit. I think a quarto-specific reader would be fantastic; otherwise I've just included plots as .png files, tables as pipe tables, etc.

[alesvomacka]

@clroberts-adfg This is pretty much exactly what I was after. Thanks a lot!