CSS not applied: contributes.format.html.css ignored for plain html format

Problem

The extension's contributes.format.html.css in _extension.yml is silently ignored. The quarto-openapi-table divs are generated correctly by the pre-render script, but the styles from quarto-openapi-styles.css (including overflow-x: auto) are never included in the rendered output.

This affects the bundled example project as well — even with no explicit css field in _quarto.yml, the extension's CSS is not applied.

Root cause

Quarto handles contributes.metadata and contributes.format through different code paths:

• contributes.metadata is merged globally for all installed extensions via mergeExtensionMetadata() in project-context.ts. This is why the pre-render script works.
• contributes.format is only applied via readExtensionFormat() in render-contexts.ts, which is gated on the document's format explicitly naming the extension (e.g., format: quarto-openapi-html). For plain format: html, the extension's format contributions are never read.

Since no document ever declares format: quarto-openapi-html, the contributes.format.html.css block in _extension.yml is effectively dead code — regardless of whether the consuming project has its own CSS or not.

Suggested fix

Replace the contributes.format CSS declaration with a Lua filter that injects the stylesheet via quarto.doc.add_html_dependency(), which operates at render time and is always applied.

1. Add a Lua filter (e.g., style-inject.lua):

function Meta(meta)
  quarto.doc.add_html_dependency({
    name = "quarto-openapi-styles",
    version = "0.2.0",
    stylesheets = { "quarto-openapi-styles.css" }
  })
end

2. Update _extension.yml:

title: quarto-openapi
author: Posit Software, PBC
version: 0.2.1
quarto-required: ">=1.6.0"
contributes:
  metadata:
    project:
      pre-render:
        - _extensions/posit-dev/quarto-openapi/openapi-to-markdown.ts
  filters:
    - style-inject.lua

Remove the format block — the Lua filter handles CSS injection now.

Workaround

Until this is fixed, consuming projects can manually include the extension's CSS in their _quarto.yml:

format:
  html:
    css:
      - _extensions/posit-dev/quarto-openapi/quarto-openapi-styles.css

Inspect _extension.yml, the existing openapi-to-markdown.ts pre-render entry, and quarto-openapi-styles.css first. Render the bundled example project with plain HTML to confirm the current omission, then verify that the stylesheet is included without a consuming project's explicit CSS configuration.