Custom format not found in ignored subdir

[cscheid]

Discussed in #13426

^{Originally posted by andrewpbray September 25, 2025}

Description

I use custom formats widely in a website and in general they render just fine with all of the extensions installed via quarto add at the root of the project. Today I tried ignoring one of the subdirectories and suddenly the enclosed qmds were not able to find the extension on render.

I've created a minimal reprex repo that demonstrates the issue:

https://github.com/andrewpbray/ignored-extension

which is just the boilerplate website with quarto add mcanouil/quarto-letter added as as well as _ignored/custom-doc.qmd, which uses format: letter-pdf. It renders fine if the file is named ignored/custom-doc.qmd but as is it throws:

ERROR: Unable to read the extension 'letter'.
Please ensure that you provided the correct id and that the extension is installed.

If you move the file to the root of the project it also renders fine.

Any idea what's up?

====

I'm running MacOS Sonoma with Quarto 1.7.32

[mcanouil]

Reposting:

I just cloned the repository. It appears that ignored documents can no longer access any extensions (formats, filters, shortcodes, etc.).

"ignored" either using _ prefix or with:

project:
  render: 
    - "*.qmd"
    - "!ignorable/**.qmd"

Tested using 1.9.2 (dev)

[mcanouil]

This is actually a duplicate of:

• Filter extensions fail to load if source file is in a folder that begins with underscore #6684