fix for #1468

base/doc/ltnews40.tex

@@ -458,6 +458,18 @@ \subsection{\pkg{longtable}: Extend caption type}
   {\endlongtable}
 \end{verbatim}
 
+
+\subsection{\pkg{array}: Improve \texttt{>\{...\}} specifier}
+
+If the argument of \texttt{>\{...\}} ended with a command accepting a
+trailing optional argument, e.g., defined for example with
+\verb=\NewDocumentCommand\foo{o}{...}=, one could get low-level
+parsing errors. This has now been corrected.
+%
+\githubissue{1468}
+
+
+
 %\section{Changes to files in the \pkg{cyrillic} category}
 
 \begin{thebibliography}{9}\frenchspacing

required/tools/array.dtx

@@ -39,7 +39,7 @@
 %    \begin{macrocode}
 %<+package>\NeedsTeXFormat{LaTeX2e}[2024/06/01]
 %<+package>\ProvidesPackage{array}
-%<+package>         [2024/07/13 v2.6e Tabular extension package (FMi)]
+%<+package>         [2024/09/17 v2.6f Tabular extension package (FMi)]
 %
 % \fi
 %
@@ -1387,8 +1387,12 @@ Bug reports can be opened (category \texttt{#1}) at\\%
 %    \end{macrocode}
 %    Here, we assume that the \textsf{count} register
 %    =\@tempcnta= has saved the value $=\count@= - 1$.
+%
+%    We end with \cs{relax} to stop any parsing for optional
+%    arguments out of \verb=>{...}= at this point. 
+% \changes{v2.6f}{2024/09/13}{Stop parsing for optional argument (gh/1468)}
 %    \begin{macrocode}
-   \the@toks \the \@tempcnta
+   \the@toks \the \@tempcnta \relax
 %    \end{macrocode}
 %    Next follows the =#= sign which specifies the place
 %    where the text of the column shall be inserted. To avoid
@@ -1442,7 +1446,10 @@ Bug reports can be opened (category \texttt{#1}) at\\%
 %    \begin{macrocode}
 \def\insert@pcolumn{%
    \UseTaggingSocket{tbl/pcell/begin}%
-   \the@toks \the \@tempcnta
+%    \end{macrocode}
+% \changes{v2.6f}{2024/09/13}{Stop parsing for optional argument (gh/1468)}
+%    \begin{macrocode}
+   \the@toks \the \@tempcnta \relax
    \ignorespaces \@sharp \unskip
    \the@toks \the \count@ \relax
    \UseTaggingSocket{tbl/pcell/end}%

required/tools/changes.txt

@@ -5,6 +5,12 @@ completeness or accuracy and it contains some references to files that
 are not part of the distribution.
 =======================================================================
 
+2024-09-18  Frank Mittelbach  <[email protected]>
+
+	* array.dtx (section{The insertion of declarations ...}):
+	Stop parsing too far for an optional argument if >{...} ends in a command
+	with a trailing optional arg (gh/1468)
+
 2024-09-17  Ulrike Fischer  <[email protected]>
 	* multicol.dtx: add tagging support  (tagging/705)
 

required/tools/testfiles/github-1468.lvt

@@ -0,0 +1,28 @@
+% https://github.com/latex3/latex2e/issues/1468
+
+\documentclass{article}
+\usepackage{array}
+
+\input{test2e}
+
+
+\begin{document}
+
+$x$  % init fonts
+
+\START
+
+\newcommand\foo[1][]{x}
+
+\begin{tabular}{>{\foo}l<{\foo}>{\foo}p{2cm}<{\foo}}
+  Foo & Bar \\
+\end{tabular}
+
+\RenewDocumentCommand\foo{o}{x}
+
+\begin{tabular}{>{\foo}l<{\foo}>{\foo}p{2cm}<{\foo}}
+  Foo & Bar \\
+\end{tabular}
+
+\end{document}
+

required/tools/testfiles/github-1468.tlg

@@ -0,0 +1,4 @@
+This is a generated file for the LaTeX2e validation system.
+Don't change this file in any respect.
+[1
+] (github-1468.aux)