fix: Typst extension logo path resolution in subdirectories (#13917)

[gordonwoodhull]

Summary

• Fixes extension logo paths being incorrectly double-prefixed with project offset when rendering from subdirectories
• Extension-resolved paths (containing _extensions or starting with ..) are already input-relative and should not have projectOffset() applied
• Adds test case verifying extension logos work correctly from subdirectories

Problem

When using a custom Typst format extension with a logo, rendering from a subdirectory fails:

metadata
  logo: ../_extensions/issue/quarto-icon.svg  # correct input-relative path

error: failed to load file (access denied)
    image("../../_extensions/issue/quarto-icon.svg")  # incorrectly double-prefixed
    = hint: cannot read file outside of project root

The bug was introduced in commit 533784522 which added projectOffset() to logo paths for brand.yml support, but incorrectly applied it to all logo paths including extension-resolved ones.

Solution

In src/resources/filters/quarto-post/typst-brand-yaml.lua, detect extension-resolved paths and skip the project offset:

if imageFilename[1] ~= "/" and _quarto.projectOffset() ~= "." then
  local is_extension_path = string.find(imageFilename, "_extensions") or
    string.sub(imageFilename, 1, 2) == ".."
  if not is_extension_path then
    local offset = _quarto.projectOffset()
    imageFilename = pandoc.path.join({offset, imageFilename})
  end
end

This is the same pattern used in PR #13902 for font-paths.

Related

• Same underlying issue as In custom typst format extension, relative or project relative font-paths not working #13745 / PR fix: resolve relative font-paths in typst extensions (#13745) #13902 (font-paths)
• See plans/brand-extension-path-resolution.md for detailed analysis of both path systems

Fixes #13917

Test plan

• New smoke test in tests/docs/smoke-all/typst/extension-logo/ verifies correct path in generated .typ file
• CI tests pass

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[mcanouil]

FWI, the issue does not seem limited to logo, other resources are impacted.

I updated my reprex:

git clone --filter=blob:none --sparse https://github.com/mcanouil/quarto-issues-experiments.git
cd quarto-issues-experiments
git sparse-checkout set quarto-cli-13917

Extensions resources should never have ../ prepended to them.
Extensions are at the root and it seems --root is set to _quarto.yml location when sent to typst, so the paths have no reasons to get project offset when in a project and when Quarto extensions resources from my understanding.