Italics leak with onchar=fonts and CJK

[dcpurton]

I came across a weird issue when trying to answer https://tex.stackexchange.com/q/761269/87678

In the following example, English is in italics unless I specify both the CJK italic font and a FakeSlant.

% TeX program = lualatex
\documentclass{article}
\usepackage{babel}
\babelprovide[import, main]{chinese-simplified}
\babelprovide[import, onchar=ids fonts]{english}
\babelfont[english]{rm}{Latin Modern Roman}
\babelfont[chinese-simplified]{rm}[
    %ItalicFont = {AR PL SungtiL GB},
    %ItalicFeatures = {FakeSlant=0}
  ]{AR PL SungtiL GB}
\begin{document}
English \emph{中文}
\end{document}

[jbezos]

This is similar to #178. I fixed it for families, but not for shapes. As you’ve discovered, a workaroud is to add a feature (even a dummy one works). I'll see how to fix it.