xpinyin会影响xeCJK的Autofallback机制

Reproduce the issue with the shown test.tex document and xelatex, comparing the output with and without xpinyin. Start by reading xpinyin.sty alongside xeCJK.sty to trace the interaction; it is done when xeCJK's AutoFallBack still selects FandolSong-Regular.otf while xpinyin continues to add pinyin.

考虑下面的两个MWE：

\documentclass{article}
\usepackage[AutoFallBack]{xeCJK}
\setCJKmainfont{lmroman10-regular.otf}
\setCJKfallbackfamilyfont{\CJKrmdefault}{FandolSong-Regular.otf}

\begin{document}
China 中国

\end{document}

work.

然而如果引入 xpinyin：

\documentclass{article}
\usepackage[AutoFallBack]{xeCJK}
\setCJKmainfont{lmroman10-regular.otf}
\setCJKfallbackfamilyfont{\CJKrmdefault}{FandolSong-Regular.otf}
\usepackage{xpinyin}

\begin{document}
China 中国

China \xpinyin*{中国}
\end{document}

得到的效果如下：

终端的输出为：

$ xelatex test
This is XeTeX, Version 3.141592653-2.6-0.999998 (TeX Live 2026) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(./test.tex
LaTeX2e <2026-06-01>
L3 programming layer <2026-06-18>
(c:/texlive/2026/texmf-dist/tex/latex/base/article.cls
Document Class: article 2025/01/22 v1.4n Standard LaTeX document class
(c:/texlive/2026/texmf-dist/tex/latex/base/size10.clo))
(c:/texlive/2026/texmf-dist/tex/xelatex/xecjk/xeCJK.sty
(c:/texlive/2026/texmf-dist/tex/latex/l3kernel/expl3.sty
(c:/texlive/2026/texmf-dist/tex/latex/l3backend/l3backend-xetex.def))
(c:/texlive/2026/texmf-dist/tex/latex/ctex/ctexhook.sty)
(c:/texlive/2026/texmf-dist/tex/latex/l3packages/xtemplate/xtemplate.sty)
(c:/texlive/2026/texmf-dist/tex/latex/fontspec/fontspec.sty
(c:/texlive/2026/texmf-dist/tex/latex/l3packages/xparse/xparse.sty)
(c:/texlive/2026/texmf-dist/tex/latex/fontspec/fontspec-xetex.sty
(c:/texlive/2026/texmf-dist/tex/latex/base/fontenc.sty)
(c:/texlive/2026/texmf-dist/tex/latex/fontspec/fontspec.cfg)))
(c:/texlive/2026/texmf-dist/tex/xelatex/xecjk/xeCJK.cfg))
(c:/texlive/2026/texmf-dist/tex/latex/xpinyin/xpinyin.sty
(c:/texlive/2026/texmf-dist/tex/latex/xpinyin/xpinyin-database.def))
(./test.aux)
Missing character: There is no 中 (U+4E2D) in font [lmroman10-regular.otf]/OT:sc
ript=hani;language=dflt;!
Missing character: There is no 国 (U+56FD) in font [lmroman10-regular.otf]/OT:sc
ript=hani;language=dflt;!
[1] (./test.aux)

 *File List*
 article.cls    2025/01/22 v1.4n Standard LaTeX document class
  size10.clo    2025/01/22 v1.4n Standard LaTeX file (size option)
   xeCJK.sty    2026/07/06 v3.10.2 Typesetting CJK scripts with XeLaTeX
   expl3.sty    2026-06-18 L3 programming layer (loader) 
l3backend-xetex.def    2026-02-18 L3 backend support: XeTeX
ctexhook.sty    2026/07/04 v2.6.2 Document and package hooks (CTEX)
xtemplate.sty    2025-10-09 L3 Experimental prototype document functions
fontspec.sty    2025/09/29 v2.9g Font selection for XeLaTeX and LuaLaTeX
  xparse.sty    2025-10-09 L3 Experimental document command parser
fontspec-xetex.sty    2025/09/29 v2.9g Font selection for XeLaTeX and LuaLaTeX
 fontenc.sty    2025/07/18 v2.1d Standard LaTeX package
fontspec.cfg
   xeCJK.cfg    2026/07/06 v3.10.2 Configuration file for xeCJK package
 xpinyin.sty    2022/07/14 v3.1 Automatically add pinyin to Chinese characters
xpinyin-database.def    2022/07/14 v3.1 xpinyin database
 ***********

 )
Output written on test.pdf (1 page).
Transcript written on test.log.