Typst writer: leading-dot string arguments get an invalid backslash prepended

[cderv]

A string that starts with a literal . gets a spurious \ prepended when the Typst writer emits it as a string-literal argument. The clearest case is a relative --bibliography path, but it hits any leading-dot string routed through escapeTypst (image paths, etc.).

Command and input:

printf 'test\n' | pandoc -s -f markdown -t typst --bibliography=../refs.bib

What pandoc emits:

#bibliography(("\../refs.bib"))

Expected #bibliography(("../refs.bib")) — a clean forward-slash path.

The backslash is invalid Typst. Typst 0.15 rejects it outright:

error: path must not contain a backslash
    ┌─ doc.typ:151:14
    │
151 │ #bibliography(("\../refs.bib"))
    │               ^^^^^^^^^^^^^^^^
    │
    = hint: use forward slashes instead: `"/../refs.bib"`
    = hint: in earlier Typst versions, backslashes indicated path separators on Windows
    = hint: this behavior is no longer supported as it is not portable

Any leading-dot string is affected; strings without a leading dot are fine:

--bibliography=./refs.bib   →  #bibliography(("\./refs.bib"))
--bibliography=sub/refs.bib →  #bibliography(("sub/refs.bib"))     (clean)

Regression: absent in pandoc 3.8.3, present in 3.10. The commit below is in tags 3.9.0.1 / 3.9.0.2 / 3.10 but not 3.8.3.

The cause could be the leading-. rule added to escapeTypst in 80c704a (#11511, "properly escape . after bracketed argument"). That rule prepends \ before a . at the very start of a string, which is correct when the text follows a ]/) in body content (e.g. .foo → \.foo). But metadata string values are escaped through the same function — metaToContext renders them via inlinesToTypst, which calls escapeTypst — so a --bibliography path lands there too and gets the same leading \, where in a Typst string literal it's invalid:

pandoc/src/Text/Pandoc/Writers/Typst.hs

Lines 611 to 621 in 5dd1910

	escapeTypst :: Bool -> EscapeContext -> Text -> Doc Text
	escapeTypst smart context t =
	(case T.uncons t of
	Just (c, rest)
	| c == ';' -> char '\\' -- see #9252
	| c == '.'
	, not (T.null rest) -> char '\\' -- see #11511
	| needsEscapeAtLineStart c || isOrderedListMarker t
	-> afterBreak "\\"
	_ -> mempty) <>
	literal (snd $ T.foldl' go ('\n', mempty) t)

Where the right fix belongs (making the leading-. escape context-aware, or not routing verbatim path arguments through escapeTypst) is your call — I may be missing the context that rule guards against.

Version: pandoc 3.10 on Windows 11.

[jgm]

This is a tricky one. Pandoc renders everything in metadata as if it's ordinary text, but this poses a problem in the current case, since typst's escaping rules inside a string or path context are different than for ordinary text. Probably the most straightforward fix would be to roll back 80c704a and replace it with something more subtle, but the replacement isn't obvious, and I'm not sure there wouldn't be other similar problems.

A workaround (if you're not generating multiple formats) is to specify the bibliography as raw typst:

bibliography: `./refs.bib`{=typst}

If you are generating multiple formats, you could use a Lua filter to set the format appropriately.

[cderv]

If you are generating multiple formats, you could use a Lua filter to set the format appropriately.

I think for quarto, I am going with this and change the metadata within Lua.

[jgm]

Also related: #7414