Report a clear error when a font fallback crashes lualatex#14560
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On recent TeX Live (luaotfload v3.29), setting a font fallback (mainfontfallback/monofontfallback/...) crashes LuaLaTeX before a PDF is produced: luaotfload's fallback resolver dereferences a nil font. Quarto only showed a generic "compilation failed" with no usable signal, because the crash is a Lua runtime error with no standard "! ...Here is how much" block for the log parser to key off. Detect the crash signature in findLatexError and return a message that names the fallback options, explains it is a known upstream luaotfload bug on this TeX Live, and points to the single-font workaround. Upstream report: latex3/luaotfload#331 See #14553.
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When a document sets a font fallback (
mainfontfallback,monofontfallback, ...) and renders to PDF with lualatex on recent TeX Live (luaotfload v3.29), lualatex crashes before producing a PDF and Quarto reports only a genericcompilation failed- error.Root Cause
luaotfload's fallback resolver appends an internal
;-fallbackfeature to each fallback entry and resolves it withdefine_font, which returnsnilon this version;luaotfload-fallback.luathen dereferences thenil. The crash is a Lua runtime error with no! ...Here is how muchblock, sofindLatexErrorinsrc/command/render/latexmk/parse-error.tsextracts nothing and the user is left with a generic failure and no signal.Fix
Detect the crash signature in
findLatexErrorand return an actionable message: it names the fallback options, explains it is a known upstream luaotfload bug on this TeX Live, and points to the single-font workaround (e.g.monofont: JuliaMono). Upstream report: latex3/luaotfload#331This is a diagnostic only — the underlying crash is upstream. The single-font workaround renders correctly today.
Test Plan
monofont+monofontfallbackon lualatex (TeX Live 2026) — the error names the fallback options and links the upstream issue, instead of a generic failuretests/unit/latexmk/parse-error.test.tscovers the crash-log signatureRelated to #14553