\sffamily after \fontseriesforce + \selectfont

[aminophen]

Brief outline of the bug

The behavior of \sffamily changed after \fontseriesforce{something}\selectfont, between 2020-10-01 and 2021-06-01. Maybe related to #444 but I don't know whether this is an intended change.

Minimal example showing the bug

%#!pdflatex
\RequirePackage{latexbug}
%\RequirePackage[2020/10/01]{latexrelease}
\documentclass{article}
\makeatletter
\DeclareFontFamily{OT1}{hoge}{}
\DeclareFontShape {OT1}{hoge}{m} {n}{<-> s*cmff10}{}
\DeclareFontShape {OT1}{hoge}{ub}{n}{<-> s*cmsl10}{}
\DeclareFontFamily{OT1}{fuga}{}
\DeclareFontShape {OT1}{fuga}{m} {n}{<-> s*cmfi10}{}
\DeclareFontShape {OT1}{fuga}{sb}{n}{<-> s*cmbxsl10}{}

\def\rmdefault{hoge}\def\sfdefault{fuga}
\def\bfseries@rm{ub}\def\bfseries@sf{sb}
\def\test#1{%
  \par\begingroup#1%
    \xdef\status@af{\f@family/\f@series/\f@shape}%
  123\space\endgroup%
  (\texttt{\status@af})
}
\begin{document}

\test{}
% => hoge/m/n

\test{\fontseries{ub}\selectfont\sffamily}
% => fuga/sb/n

\test{\fontseriesforce{ub}\selectfont\sffamily}
% => changed!
%  * 2020-10-01: fuga/ub/n (fallback -> fuga/m/n)
%  * 2021-06-01: fuga/sb/n

\end{document}

Log file (required) and possibly PDF file

• TL2020 frozen (LaTeX2e 2020-10-01 patch level 4): series-tl2020.log
• Latest (LaTeX2e 2021-06-01): series-20210601.log

[user227621]

I think that this happens because the "force state" is now reset after every \selectfont. See here:

the force should always be reset by \selectfont not by the next \fontseries

This change was made because not resetting the "forced state" could lead to strange effects: See Issue 3 in this comment.

[aminophen]

@user227621 Thanks for the explanation; now I understand your point well.

[FrankMittelbach]

Yes this is the intended behavior and before it was wrong as the scope of the "force" was not well defined. Now it applies to the next \selectfontas it should.