Markdown in custom listing fields not rendered by EJS template

[andrewheiss]

Bug description

Following the "Metadata Listings" section in the documentation, it is possible to include custom metadata in YAML, either in individual files or in front matter, and have that metadata show up in a custom listing template.

For instance, we can create a listing page:

index.qmd

---
title: "Testing"
template: custom.ejs
contents:
- name: First Item
  href: https://www.quarto.org
  custom-field: A **custom value**
- name: Second Item
  href: https://www.rstudio.org
  custom-field: A *second* custom value
---

Blah

…and a custom EJS template:

custom.ejs

```{=html}
<ul>
<% for (const item of items) { %>
  <li>
    <a href="<%- item.href %>"><%= item.name %></a><br/>
    <%= item['custom-field'] %>
  </li>
<% } %>
</ul>
```

…and it will render the custom field in an HTML list:

<ul>
        <li>
            <a href="https://www.quarto.org/">
                First Item
            </a><br>
            A **custom value**
        </li>
        <li>
            <a href="https://www.rstudio.org/">
                Second Item
            </a><br>
            A *second* custom value
        </li>
</ul>

However, any Markdown formatting in the custom field is not rendered—it renders the text as A **custom value** instead of A <strong>custom value</strong>

It could be helpful to have a helper function of sorts accessible by EJS files, like

<%= parseMarkdown(item['custom-field']) %>

Rendering works as expected when raw HTML is used in the metadata. That is,

- name: First Item
  href: https://www.quarto.org
  custom-field: A <strong>custom value</strong>

… turns into

<li>
    <a href="https://www.quarto.org/">
        First Item
    </a><br>
    A <strong>custom value</strong>
</li>

---

This is with Quarto 1.3.26 in RStudio 2022.07.2+576 (and also in VS Code) on macOS Monterey 12.6

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.

[dfolio]

Dear all
I guess the following issue is also related to this bug:
If you use some metadata variable in the YAML‌ front matter it is not evaluated in the listing

Example of index.qmd:

---
title: An example
doi: example.of.doi
links:
  - name: "DOI"
    href: https://doi.org/{{< meta doi >}}
---

with custom.ejs

<ul>
<% for (const item of items) { %>
  <li <%=metadataAttrs(item) %>>
  <% if (item.links) { %>
    <% for (const link of item.links) { %>
     <a href="<%- link.href %>" >&nbsp;<%= link.name %></a>
    <% } %>
 <% }  %>
  </li>
<% } %>
</ul>

Lead to

<li><a href="https://doi.org/%7B%7B%3C%20meta%20doi%20%3E%7D%7D"> DOI</a></li>

with <a href="<%= link.href %>" >&nbsp;<%= link.name %></a>, I get https://doi.org/?meta:doi, with a warning:

WARNING: Unknown meta key doi specified in a metadata Shortcode.

Note:

This work properly with template partials

Example of title-metadata.html

 $for(links)$
    <a href="$links.href$" > $links.name$</a>
  $endfor$

Render properly:

<a href="https://doi.org/example.of.doi">DOI</a>