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Install hyphenation package when babel fails with an undefined language - #15029
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With `lang: de-CH` and no hyphen-german installed, babel-german checks
`\iflanguage{ngerman}` at begin document, and babel raises a fatal
"You haven't defined the language 'ngerman' yet" error. Missing hyphenation
patterns were only handled as babel warnings on a successful compile, so the
failure branch found nothing to install and gave up.
Detect this error on the failure path and install the matching
`hyphen-<lang>` package directly by name, reusing the language-to-package
mapping of findMissingHyphenationFiles (now a shared helper).
Fixes rstudio/tinytex#515
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPRhHuCKXMd1s1wZgEe1M4
The test now removes hyphen-german and babel-german only on CI, so the CI run exercises the auto-installation path, and local runs no longer uninstall packages from the developer's TinyTeX. The document and the changelog entry now point at the quarto-cli issue.
The language name in babel messages comes from the LaTeX log and ends up as a tlmgr argument. On Windows tlmgr.bat is called through a temporary .bat file, and requireQuoting() does not handle `"`, `%`, `^` or `!`, so a crafted name in a document's log could be interpreted by cmd. Every hyphenation name in texlive.tlpdb (102 names and synonyms) is made of lowercase letters, digits and hyphens, so names that don't match ^hyphen-[a-z0-9-]+$ are dropped. This applies to both the babel error and the older babel warning detection, which share the mapping function. Same validation as rstudio/tinytex#516.
Only ngerman was mapped, so any other pattern name whose package is not hyphen-<name> asked tlmgr for a package that doesn't exist, e.g. swissgerman (hyphen-german), nynorsk (hyphen-norwegian) or hindi (hyphen-indic). The table lists every such name from the `execute AddHyphen` lines (name= and synonyms=) of the current texlive.tlpdb: 16 pattern names, 9 older synonyms and 12 Indic languages, 37 in total. That's the same table as rstudio/tinytex#516. The 4 german-x-* names provided by dehyph-exptl are left out, as they are not hyphen-* packages. Names are lowercased before the lookup, since language.dat uses mixed case names such as UKenglish.
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This was referenced Oct 13, 2026
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The hyphenation table in parse-error.ts was a hand copy of tinytex's
and had drifted. With `\begin{hyphenrules}{ngerman-x-latest}` and no
dehyph-exptl installed, babel stops with "You haven't defined the
language 'ngerman-x-latest' yet". The package was always built as
`hyphen-<name>`, so tlmgr was asked for the non-existent
`hyphen-ngerman-x-latest` and the render failed.
Detection now follows tinytex main (rstudio/tinytex#517, follow-up to
rstudio/tinytex#516), and builds on #15029:
- The map holds full package names, with the 4 dehyph-exptl entries, and
the language name is validated instead of the resulting package name.
- A language given as a description keeps its first word, so "German
(current orthography)" gives hyphen-german.
- The babel regex only reads warning blocks, so a (babel) continuation
of an Info message can't produce a package.
- Every warned language is installed, not only the first, and
polyglossia warnings are detected.
- The daily TinyTeX workflow also compares tinytex's hyphen.json. It
reports a skipped comparison when the download fails, and an invalid
hyphen.json fails the first run instead of being cached.
The chinese skip list (#10291), the `\l@nil` fallback and unquoted names
in the babel error regex are kept.
Fixes #15035
See #15027, rstudio/tinytex#518
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When rendering to PDF with
lang: de-CHon a TinyTeX without German hyphenation patterns, Quarto installsbabel-germanbut the compilation still fails, andhyphen-germanis never installed:This was first reported in rstudio/tinytex#515, and rstudio/tinytex#516 fixes it in the R package. This PR ports the same changes to Quarto.
Root cause
Missing hyphenation patterns usually show up as a babel warning, which
findMissingHyphenationFiles()already handles after a successful compilation. Withlang: de-CH, babel-german definesnswissgermanand then checks\iflanguage{ngerman}, which is a fatal error whenhyphen-germanis not installed. The error is not about a missing file, so thetlmgr searchbased detection finds nothing to install.Fix
findMissingHyphenationPackages()detects the babel error and the hyphenation package is installed by name with the other missing packages, without atlmgr search.execute AddHyphenentries oftexlive.tlpdb. Some names are in a package with another name, e.g.swissgermaninhyphen-german,nynorskinhyphen-norwegian, and all Indic languages inhyphen-indic. Onlyngermanwas mapped before. The table was checked against the currenttexlive.tlpdbfrom CTAN (same 37 names as in Install hyphen-* packages when babel can't define the language rstudio/tinytex#516).tlmgr, so only names matching^hyphen-[a-z0-9-]+$are kept. On Windows,tlmgr.batis called through a temporary.batfile andrequireQuoting()does not handle",%,^or!. I did not try to exploit it, this is from reading the code. All hyphenation names intexlive.tlpdbpass this filter. It also applies to the existing babel warning detection, which shares the mapping.The
german-x-*names fromdehyph-exptlare not handled, as they are nothyphen-*packages. This is the same in rstudio/tinytex#516.The new smoke test removes
hyphen-germanandbabel-germanbefore rendering, only on CI, so local runs don't modify the TinyTeX installation.Fixes #15027
Checklist
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texlive.tlpdbfrom CTANNote: autonomous AI agents submitting PRs without human oversight are not permitted — see the Code of Conduct.