看来 beamer 中的 \InputIfFileExists 问题仍然存在。编译：
\listfiles
\documentclass{beamer}
\begin{document}
\begin{frame}
\frametitle{Test}
some text $\mathbf{A}$.
\end{frame}
\end{document}
在使用 XeLaTeX 编译器（最近的 MikTeX）进行两次编译后，我收到警告（使用 pdfLaTeX 引擎进行编译除了这次警告外还给出了另外四个警告，结果也不同）；
LaTeX Warning: Command \InputIfFileExists has changed.
Check if current package is valid.
我使用最新的 MikTeX 进行了测试。上述 MWE 中使用的文件列表如下：
*File List*
beamer.cls 2020/07/22 v3.59 A class for typesetting presentations
beamerbasemodes.sty
etoolbox.sty 2020/08/24 v2.5j e-TeX tools for LaTeX (JAW)
beamerbasedecode.sty
ifpdf.sty 2019/10/25 v3.4 ifpdf legacy package. Use iftex instead.
iftex.sty 2020/03/06 v1.0d TeX engine tests
beamerbaseoptions.sty
keyval.sty 2014/10/28 v1.15 key=value parser (DPC)
geometry.sty 2020/01/02 v5.9 Page Geometry
ifvtex.sty 2019/10/25 v1.7 ifvtex legacy package. Use iftex instead.
geometry.cfg
size11.clo 2019/12/20 v1.4l Standard LaTeX file (size option)
pgfcore.sty 2020/01/08 v3.1.5b (3.1.5b)
graphicx.sty 2019/11/30 v1.2a Enhanced LaTeX Graphics (DPC,SPQR)
graphics.sty 2019/11/30 v1.4a Standard LaTeX Graphics (DPC,SPQR)
trig.sty 2016/01/03 v1.10 sin cos tan (DPC)
graphics.cfg 2016/06/04 v1.11 sample graphics configuration
xetex.def 2020/08/26 v5.0i Graphics/color driver for xetex
pgfsys.sty 2020/01/08 v3.1.5b (3.1.5b)
pgfrcs.sty 2020/01/08 v3.1.5b (3.1.5b)
everyshi.sty 2001/05/15 v3.00 EveryShipout Package (MS)
pgfrcs.code.tex
pgfsys.code.tex
pgfsyssoftpath.code.tex 2020/01/08 v3.1.5b (3.1.5b)
pgfsysprotocol.code.tex 2020/01/08 v3.1.5b (3.1.5b)
xcolor.sty 2016/05/11 v2.12 LaTeX color extensions (UK)
color.cfg 2016/01/02 v1.6 sample color configuration
pgfcore.code.tex
xxcolor.sty 2003/10/24 ver 0.1
atbegshi.sty 2019/12/05 v1.19 At begin shipout hook (HO)
infwarerr.sty 2019/12/03 v1.5 Providing info/warning/error messages (HO)
ltxcmds.sty 2019/12/15 v1.24 LaTeX kernel commands for general use (HO)
hyperref.sty 2020-05-15 v7.00e Hypertext links for LaTeX
pdftexcmds.sty 2020-06-27 v0.33 Utility functions of pdfTeX for LuaTeX (HO)
kvsetkeys.sty 2019/12/15 v1.18 Key value parser (HO)
kvdefinekeys.sty 2019-12-19 v1.6 Define keys (HO)
pdfescape.sty 2019/12/09 v1.15 Implements pdfTeX's escape features (HO)
hycolor.sty 2020-01-27 v1.10 Color options for hyperref/bookmark (HO)
letltxmacro.sty 2019/12/03 v1.6 Let assignment for LaTeX macros (HO)
auxhook.sty 2019-12-17 v1.6 Hooks for auxiliary files (HO)
kvoptions.sty 2019/11/29 v3.13 Key value format for package options (HO)
pd1enc.def 2020-05-15 v7.00e Hyperref: PDFDocEncoding definition (HO)
intcalc.sty 2019/12/15 v1.3 Expandable calculations with integers (HO)
etexcmds.sty 2019/12/15 v1.7 Avoid name clashes with e-TeX commands (HO)
url.sty 2013/09/16 ver 3.4 Verb mode for urls, etc.
bitset.sty 2019/12/09 v1.3 Handle bit-vector datatype (HO)
bigintcalc.sty 2019/12/15 v1.5 Expandable calculations on big integers (HO)
hxetex.def 2020-05-15 v7.00e Hyperref driver for XeTeX
puenc.def 2020-05-15 v7.00e Hyperref: PDF Unicode definition (HO)
stringenc.sty 2019/11/29 v1.12 Convert strings between diff. encodings (HO)
rerunfilecheck.sty 2019/12/05 v1.9 Rerun checks for auxiliary files (HO)
atveryend.sty 2019-12-11 v1.11 Hooks at the very end of document (HO)
uniquecounter.sty 2019/12/15 v1.4 Provide unlimited unique counter (HO)
se-ascii-print.def 2019/11/29 v1.12 stringenc: Printable ASCII characters
beamerbaserequires.sty
beamerbasecompatibility.sty
beamerbasefont.sty
amssymb.sty 2013/01/14 v3.01 AMS font symbols
amsfonts.sty 2013/01/14 v3.01 Basic AMSFonts support
sansmathaccent.sty 2020/01/31
scrlfile.sty 2018/12/30 v3.26a KOMA-Script package (loading files)
beamerbasetranslator.sty
translator.sty 2020-08-03 v1.12c Easy translation of strings in LaTeX
beamerbasemisc.sty
beamerbasetwoscreens.sty
beamerbaseoverlay.sty
beamerbasetitle.sty
beamerbasesection.sty
beamerbaseframe.sty
beamerbaseverbatim.sty
beamerbaseframesize.sty
beamerbaseframecomponents.sty
beamerbasecolor.sty
beamerbasenotes.sty
beamerbasetoc.sty
beamerbasetemplates.sty
beamerbaseauxtemplates.sty
beamerbaseboxes.sty
beamerbaselocalstructure.sty
enumerate.sty 2015/07/23 v3.00 enumerate extensions (DPC)
beamerbasenavigation.sty
beamerbasetheorems.sty
amsmath.sty 2020/01/20 v2.17e AMS math features
amstext.sty 2000/06/29 v2.01 AMS text
amsgen.sty 1999/11/30 v2.0 generic functions
amsbsy.sty 1999/11/29 v1.2d Bold Symbols
amsopn.sty 2016/03/08 v2.02 operator names
amsthm.sty 2020/05/29 v2.20.6
beamerbasethemes.sty
beamerthemedefault.sty
beamerfontthemedefault.sty
beamercolorthemedefault.sty
beamerinnerthemedefault.sty
beamerouterthemedefault.sty
l3backend-xetex.def 2020-09-01 L3 backend support: XeTeX
ts1cmr.fd 2019/12/16 v2.5j Standard LaTeX font definitions
nameref.sty 2019/09/16 v2.46 Cross-referencing by name of section
refcount.sty 2019/12/15 v3.6 Data extraction from label references (HO)
gettitlestring.sty 2019/12/15 v1.6 Cleanup title references (HO)
beamer-test.out
beamer-test.out
translator-basic-dictionary-English.dict
translator-bibliography-dictionary-English.dict
translator-environment-dictionary-English.dict
translator-months-dictionary-English.dict
translator-numbers-dictionary-English.dict
translator-theorem-dictionary-English.dict
umsa.fd 2013/01/14 v3.01 AMS symbols A
umsb.fd 2013/01/14 v3.01 AMS symbols B
***********
Package atveryend Info: Executing hook `AtEndAfterFileList' on input line 10.
Package rerunfilecheck Info: File `beamer-test.out' has not changed.
(rerunfilecheck) Checksum: D41D8CD98F00B204E9800998ECF8427E;0.
)
警告并不重要，但有点烦人。我是否错过了 MWE 中的某些内容？我阅读了此问题的答案和评论问题，所以我想知道在此期间是否发生了一些新鲜事？