Gh 1265 (#1424)

* fix for #1265 (draft version)

* fix docu

* corrections

* add an ltnews entry

* changes entry

* typo

* fix typos

* one more

---------

Co-authored-by: David Carlisle <[email protected]>

base/doc/ltnews40.tex

@@ -289,6 +289,7 @@ \section{Improvement to \XeTeX\ \cs{showhyphens}}
 %
 \githubissue{1380}
 
+
 \section{Avoid code duplication in rollback}
 
 When the kernel uses \cs{AddToHook} in a region that might be 
@@ -302,7 +303,24 @@ \section{Avoid code duplication in rollback}
 \githubissue{1407}
 
 
-%\section{Changes to packages in the \pkg{amsmath} category}
+
+
+\section{Changes to packages in the \pkg{amsmath} category}
+
+\section{Extend support for \cs{dots}}
+
+The implementation of \cs{dots} in \pkg{amsmath} has the feature that
+it selects different dots depending on the symbol that follows: e.g.,
+dots between commas would normally be on the baseline, while dots
+between binary or relational symols would be raised. However, when symbols such
+as \cs{cong} were protected from expansion in moving arguments (so
+that they worked in places such as headings) it had the unfortunate
+side-effect that the \cs{dots} magic stopped working for them. This
+has now been corrected.
+%
+\githubissue{1265}
+
+
 
 %\section{Changes to packages in the \pkg{graphics} category}
 

required/amsmath/amsmath.dtx

@@ -85,7 +85,7 @@ Bug reports can be opened (category \texttt{#1}) at\\%
 %    \end{macrocode}
 %
 %    \begin{macrocode}
-\ProvidesPackage{amsmath}[2024/07/01 v2.17q AMS math features]
+\ProvidesPackage{amsmath}[2024/07/01 v2.17r AMS math features]
 %    \end{macrocode}
 %
 % \section{Catcode defenses}
@@ -1087,6 +1087,14 @@ Foreign command \@backslashchar#1;\MessageBreak
   \ifx9#2 \@xp\@xp\@xp\zap@to@space\fi}}}
 \def\zap@to@space#1 {}
 %    \end{macrocode}
+%    
+% \changes{v2.17r}{2024/06/29}{macro added to strip \cs{protected} (gh/1265)}
+%    \begin{macrocode}
+{\uccode`9=`\p %
+  \uppercase{\gdef\stripprotected@#1#2#3\relax{%
+      \ifx9#2 \@xp\@xp\@xp\zap@to@space\fi}}}
+%    \end{macrocode}
+%
 %    \begin{macrocode}
 \def\keybin@{\gtest@true
  \ifx\@let@token+\else\ifx\@let@token=\else
@@ -1139,15 +1147,37 @@ Foreign command \@backslashchar#1;\MessageBreak
          \gdef\thedots@{\dotsb@}%
        \else
 %    \end{macrocode}
-% \changes{v2.15d}{2016/06/28}{Add space token to prevent runaway argument error}
-%    \begin{macrocode}
-         \xdef\meaning@{\meaning\@let@token. .........}%
-%    \end{macrocode}
-% In previous versions \verb|\long| macros were not seen by the lokkahead.
+%    In case \cs{\@let@token} is a robust \LaTeXe{} command, i.e.,
+%    expands to \cs{protect}
+%    \verb*=\somename =, we save the \cs{meaning} of
+%    \verb*=\somename = in \cs{meaning@} (possibly followed by some dots that have
+%    not been consumed as arguments during the expansion).
+%    Otherwise, we save the
+%    \cs{meaning} of \cs{@let@token} in \cs{meaning@}.  The dots at the end
+%    as well as the space are
+%    used in later parts of the checking (this could probably be cleaned up a bit).
+% \changes{v2.15d}{2016/06/28}{Add space token to prevent runaway
+%    argument error}
+% \changes{v2.17r}{2024/06/29}{Drop \cs{protect} if present (gh/1265)}
+%    \begin{macrocode}
+       \begingroup
+         \def\protect{\protect}% % make it a quark
+         \xdef\meaning@{\@xp\stripprotect@\@let@token.........\stripprotect@. .........}%
+       \endgroup
+%    \end{macrocode}
+% In previous versions \verb|\long| macros were not seen by the lookahead.
 % That was bad as this file uses \verb|\(re)newcommand| for \verb|\implies| etc.
 %    \begin{macrocode}
          \xdef\meaning@@{\@xp\striplong@\meaning@\relax\meaning@}%
 %    \end{macrocode}
+%    Until now \cs{protected} macros also stopped the lookahead, e.g.,
+%    $\cong$ wasn't recognized correctly for that reason.
+%         
+% \changes{v2.17r}{2024/06/29}{Handle \cs{protected} macros in
+%    lookahead for dots (gh/1265)}
+%    \begin{macrocode}
+         \xdef\meaning@@{\@xp\stripprotected@\meaning@@\relax\meaning@@}%
+%    \end{macrocode}
 %    \begin{macrocode}
          \@xp\math@\meaning@\math@
          \ifgtest@ % if \mathxxx test
@@ -1208,6 +1238,15 @@ Foreign command \@backslashchar#1;\MessageBreak
  \thedots@}
 %    \end{macrocode}
 %
+%    The helper to generate the meaning of \cs{\@let@token}, or of its
+%    first-level expansion with \cs{protect} removed.
+% \changes{v2.17r}{2024/06/29}{Drop \cs{protect} if present (gh/1265)}
+%    \begin{macrocode}
+\def\stripprotect@#1#2\stripprotect@{\ifx#1\protect
+  \meaning#2\else \meaning\@let@token \fi}
+
+%    \end{macrocode}
+%
 %    The \qc{\=} character is necessary in the two \cs{let} assignments
 %    in \cs{boldsymboldots@}, because the symbol we are making
 %    bold might be an \qc{\=} sign.

required/amsmath/changes.txt

@@ -2,6 +2,12 @@
 All changes above are only part of the development branch for the next release.
 ================================================================================
 
+2024-08-02  Frank Mittelbach  <[email protected]>
+
+	* amsmath.dtx (section{Ellipsis dots}):
+	Support special \dots magic in case of robust symbols protected with
+	\protected or via \DeclareRobustCommand (gh/1265)
+
 #########################
 # 2024-06-01 Release
 #########################

required/amsmath/testfiles/github-1265.lvt

@@ -0,0 +1,27 @@
+\documentclass{article}
+
+\input{test2e}
+
+% Any preamble code goes here
+\usepackage{amsmath}
+
+\showoutput
+
+\newbox\testbox
+
+\begin{document}
+
+% Demonstration of issue here
+
+\START
+
+\savebox\testbox{$\equiv\dots\equiv$}
+
+\box\testbox
+
+\savebox\testbox{$\cong\dots\cong$}
+
+\box\testbox
+
+\END
+

required/amsmath/testfiles/github-1265.tlg

@@ -0,0 +1,2 @@
+This is a generated file for the LaTeX2e validation system.
+Don't change this file in any respect.