Render Liquid tags in DescriptionGenerator before Markdown conversion

[Copilot]

The DescriptionGenerator#describe filter converts Markdown to HTML without rendering Liquid first, causing raw tags like {% local %} to appear in meta descriptions.

Changes

• Liquid preprocessing: Render Liquid tags before Markdown conversion using $site.liquid_renderer with full site payload and registers
• Error handling: Wrap in begin/rescue, fall back to original input on failure, log warning via Jekyll.logger.warn
• Backward compatibility: Only render Liquid when $site is defined

Example

Before:

<meta property="og:description" content="Meeting at {% local '2024-01-01 10:00' %}">

After:

<meta property="og:description" content="Meeting at Monday, January 1, 2024 at 10:00 AM EST">

Implementation

markdown = input.to_s

# Render Liquid tags first if $site is defined
if defined?($site) && $site
  begin
    markdown = $site.liquid_renderer.file("(cs50-describe)").parse(markdown).render!($site.site_payload, { :registers => { :site => $site } })
  rescue => e
    Jekyll.logger.warn "CS50 warning: failed to render Liquid in description: #{e.message}"
    markdown = input.to_s
  end
end

# Convert Markdown to HTML
html = $site.find_converter_instance(::Jekyll::Converters::Markdown).convert(markdown)

Original prompt

Problem: DescriptionGenerator#describe converts input Markdown to HTML but does not render Liquid first. As a result, Liquid tags (including plugin tags like {% local %}) can appear raw in generated descriptions (e.g., in meta tags).

Goal: Make a minimal change so DescriptionGenerator#describe first renders any Liquid in the input using the site's Liquid renderer and payload (so plugins/tags/filters expand), then converts the result to HTML with the Markdown converter. Keep change small and safe: wrap Liquid rendering in begin/rescue and fall back to original input on error; use $site.site_payload and registers => { :site => $site } to provide context to the renderer.

Tasks:

• Edit lib/jekyll-theme-cs50.rb: inside module CS50::DescriptionGenerator#describe, before converting to HTML, render the input string through $site.liquid_renderer.file("(cs50-describe)").parse(markdown).render!($site.site_payload, { :registers => { :site => $site } }) if $site is defined. Wrap in rescue and log a Jekyll warning if rendering fails.
• Keep all other logic unchanged.

Testing notes:

• After change, run jekyll build and confirm meta descriptions no longer contain raw Liquid tags like {% local %}.

Files to modify:

• lib/jekyll-theme-cs50.rb

Make the change and open a pull request with a concise title and description. Commit message: "Render Liquid in DescriptionGenerator before Markdown conversion".

This pull request was created as a result of the following prompt from Copilot chat.

Problem: DescriptionGenerator#describe converts input Markdown to HTML but does not render Liquid first. As a result, Liquid tags (including plugin tags like {% local %}) can appear raw in generated descriptions (e.g., in meta tags).

Goal: Make a minimal change so DescriptionGenerator#describe first renders any Liquid in the input using the site's Liquid renderer and payload (so plugins/tags/filters expand), then converts the result to HTML with the Markdown converter. Keep change small and safe: wrap Liquid rendering in begin/rescue and fall back to original input on error; use $site.site_payload and registers => { :site => $site } to provide context to the renderer.

Tasks:

• Edit lib/jekyll-theme-cs50.rb: inside module CS50::DescriptionGenerator#describe, before converting to HTML, render the input string through $site.liquid_renderer.file("(cs50-describe)").parse(markdown).render!($site.site_payload, { :registers => { :site => $site } }) if $site is defined. Wrap in rescue and log a Jekyll warning if rendering fails.
• Keep all other logic unchanged.

Testing notes:

• After change, run jekyll build and confirm meta descriptions no longer contain raw Liquid tags like {% local %}.

Files to modify:

• lib/jekyll-theme-cs50.rb

Make the change and open a pull request with a concise title and description. Commit message: "Render Liquid in DescriptionGenerator before Markdown conversion".

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.