在回答通过 fontspec 命令查询字体功能是否已激活\IfFontFeatureExists和有定义\IfFontFeatureActive。对于第二个，我没有得到可靠的结果。例如，下面说 是pnum活跃的，tnum是不活跃的，这显然不是事实。
\documentclass{article}
\usepackage[osf,tabular]{libertineRoman}
\ExplSyntaxOn
\cs_new_eq:NN \IfFontFeatureExists \fontspec_if_feature:nTF
\cs_new:Npn \mico_fontfeature_if_active:nTF #1
{ \tl_if_in:NnTF \l_fontspec_rawfeatures_sclist { #1 } }
\cs_new_eq:NN \IfFontFeatureActive \mico_fontfeature_if_active:nTF
\ExplSyntaxOff
\begin{document}
pnum \IfFontFeatureExists{pnum}{exists}{does not exist},
onum \IfFontFeatureExists{onum}{exists}{does not exist},
lnum \IfFontFeatureExists{lnum}{exists}{does not exist},
tnum \IfFontFeatureExists{tnum}{exists}{does not exist},
pnum is \IfFontFeatureActive{pnum}{}{not} active,
onum is \IfFontFeatureActive{onum}{}{not} active,
lnum is \IfFontFeatureActive{lnum}{}{not} active,
tnum is \IfFontFeatureActive{tnum}{}{not} active,
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\end{document}