Is it possible to generate metadata dynamically before render?

[benabel]

Description

On my previous websites using Gatsby or eleventy I was able to generate metadata at build time.

For example: extracting information from file path: .../1-Introduction to statistics/exercise/index.md let me get this metadata:

title: Introduction to statistics
order: 1
type: exercise
permalink: /introduction-to-statistics/exercise

This is handled by an awesome feature called data cascade in eleventy see the doc here.

Is it possible to do something similar in quarto?

[mcanouil]

Yes, you can use pre-render script and the 1.5 pre-release.

• https://quarto.org/docs/projects/scripts.html#pre-and-post-render
• https://quarto.org/docs/prerelease/1.5/pre-render.html

Note that order, type, permalink from your example are not Quarto YAML options.
See the documentation.

[benabel]

Thank you @mcanouil for these directions , I'll investigate on pre-render scripts with 1.5 version. Is there any way to change the url to a page dynamically or is it always computed from the file path?

[mcanouil]

Look for aliases/redirection that what is closer to "permalink".

https://quarto.org/docs/websites/website-navigation.html#redirects

[benabel]

It seems that manipulating permalink is not possible, also I tried setting dynamically the title with a lua filter like this:

function Meta(meta)
    local title = meta.title
    meta["title"][1]["text"] = "New title"  
    return meta
end

Title is set correctly for the document but breadcumb and navbars are not updated.

I imagine that the only way to handle this specific use is to modify the qmd files and save the changes, I think it would be nice to manipulate the metadata of files dynamically earlier. I close the discussion. Thanks for your time and this incredible program.

[mcanouil]

Some metadata are needed to actually build the structure and for Quarto to know what to build and where.
Your filter to modify the title is a bit odd but if it works.
Use format: native and look at the AST representation of the document when developing filter, it helps.

As I said, permalink does not exist, but you can define redirection in your YAML frontmatter.
I don't know if it will work to generate them dynamically in a pre-render script though.