To reproduce 

* Clone `quarto-journals/acs`
* `quarto render template.qmd`

This will error like this 
````
$ quarto render template.qmd
ERROR: La syntaxe du nom de fichier, de répertoire ou de volume est incorrecte. (os error 123), stat 'C:\Users\chris\Documents\DEV_R\quarto-journals\acs\_extensions\acs\_extensions\quarto-ext\latex-environment\C:\Users\chris\Documents\DEV_R\quarto-journals\acs\_extensions\acs\_extensions\quarto-ext\latex-environment\latex-environment.lua'

Error: La syntaxe du nom de fichier, de répertoire ou de volume est incorrecte. (os error 123), stat 'C:\Users\chris\Documents\DEV_R\quarto-journals\acs\_extensions\acs\_extensions\quarto-ext\latex-environment\C:\Users\chris\Documents\DEV_R\quarto-journals\acs\_extensions\acs\_extensions\quarto-ext\latex-environment\latex-environment.lua'
    at Object.lstatSync (deno:runtime/js/30_fs.js:305:9)
    at existsSync (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/vendor/deno.land/std@0.166.0/fs/exists.ts:75:10)
    at getFilter (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/filters.ts:682:8)
    at resolveFilterExtension (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/filters.ts:710:21)
    at resolveFilters (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/filters.ts:572:19)
    at generateDefaults (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/defaults.ts:44:35)
    at runPandoc (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/pandoc.ts:261:28)
    at renderPandoc (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/render.ts:164:30)
    at async Object.onRender (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/render-files.ts:558:30)
    at async renderFiles (file:///C:/Users/chris/Documents/DEV_R/quarto-cli/src/command/render/render-files.ts:506:13)
````

Issue is with Extension directory being prepended to an already absolute path for the filter extensions
https://github.com/quarto-dev/quarto-cli/blob/9aca80aeb66faa07f93a3939453f658ccfd25075/src/extension/extension.ts#L916-L921

In debugging session, we can see that 
* `extensions[0].path` is absolute path `"C:\\Users\\chris\\Documents\\DEV_R\\quarto-journals\\acs\\_extensions\\acs\\_extensions\\quarto-ext\\latex-environment"`
* Filter is already an absolute path : `"C:\\Users\\chris\\Documents\\DEV_R\\quarto-journals\\acs\\_extensions\\acs\\_extensions\\quarto-ext\\latex-environment\\latex-environment.lua"`

So the join does create the wrong path  in
https://github.com/quarto-dev/quarto-cli/blob/9aca80aeb66faa07f93a3939453f658ccfd25075/src/extension/extension.ts#L938

This does not happens with Shortcodes (`jss` which only have embeded shortcodes works fine). 

After a quick discussion with @dragonstyle : 

* It seems issue is not Windows specific
* Our tests seems to have miss it - maybe we need to see why
* Nothing really change in extension, but there was some heavy work on Lua filter. Maybe we resolved to absolute earlier than before or differently ? (cc @cscheid) 

Easy solution would be to not join paths if the filter path is already absolute path, but I feel this issue could be a regression from somewhere else and maybe this is not the only side effect. So I am looking.
2023-01-04T18:57:27Z
cderv
bug
closed
Lua Filters in embeded extensions is wrongly resolved 
https://github.com/quarto-dev/quarto-cli/issues/3850