Add \changes entries and latexrelease guards

base/ltfilehook.dtx

@@ -643,6 +643,8 @@
 %  kernel we  do this only now and not in \texttt{ltfiles}.
 %
 % \begin{macro}{\InputIfFileExists}
+% \begin{macro}{\@input@file@exists@with@hooks}
+% \begin{macro}{\unqu@tefilef@und}
 %    \cs{InputIfFileExists} loads any file if it is available so we
 %    have to add the hooks \texttt{file/before} and
 %    \texttt{file/after} in the right places. If the file doesn't
@@ -682,25 +684,35 @@
 %    the file name and extension are returned so that file hooks can
 %    refer to the file by their name only.  The path to the file is
 %    returned in \cs{CurrentFilePath}.
-%
-%    We pre-expand \cs{@filef@und} so that in case another file is
-%    loaded in the true branch of \cs{InputIfFileExists}, these don't
-%    change their value meanwhile. This isn't a worry with
-%    \cs[no-index]{CurrentFile...} because they are kept in a stack.
 %    \begin{macrocode}
       \edef\reserved@a{%
         \@expl@@@filehook@file@pop@assign@@nnnn
           {\CurrentFilePathUsed}%
           {\CurrentFileUsed}%
           {\CurrentFilePath}%
           {\CurrentFile}%
+%    \end{macrocode}
+%
+%    We pre-expand \cs{@filef@und} so that in case another file is
+%    loaded in the true branch of \cs{InputIfFileExists}, these don't
+%    change their value meanwhile. This isn't a worry with
+%    \cs[no-index]{CurrentFile...} because they are kept in a stack.
+%
+% \changes{v1.0d}{2020/11/17}
+%   {Move loading to \cs{@input@file@exists@with@hooks} and expand
+%    \cs{@filef@und} to avoid getting the wrong file name in the case of
+%    a substitution.}
+%    \begin{macrocode}
         \noexpand\@input@file@exists@with@hooks{\@filef@und}}%
       \expandafter\@swaptwoargs\expandafter
         {\reserved@a}%
         {#2}%
       \@expl@@@filehook@file@pop@@
     }%
 }
+%    \end{macrocode}
+%
+%    \begin{macrocode}
 \def\@input@file@exists@with@hooks#1{%
   \@addtofilelist{\unqu@tefilef@und#1\@nil}%
   \UseHook{file/before}%
@@ -743,6 +755,8 @@
 %<latexrelease>    {%
 %<latexrelease>  \expandafter\@swaptwoargs\expandafter
 %<latexrelease>      {\@filef@und}{#2\@addtofilelist{#1}\@@input}}}
+%<latexrelease>\let\@input@file@exists@with@hooks\@undefined
+%<latexrelease>\let\unqu@tefilef@und\@undefined
 %<latexrelease>\EndIncludeInRelease
 %    \end{macrocode}
 %
@@ -752,10 +766,14 @@
 %<latexrelease>\long\def \InputIfFileExists#1#2{%
 %<latexrelease>  \IfFileExists{#1}%
 %<latexrelease>    {#2\@addtofilelist{#1}\@@input \@filef@und}}
+%<latexrelease>\let\@input@file@exists@with@hooks\@undefined
+%<latexrelease>\let\unqu@tefilef@und\@undefined
 %<latexrelease>\EndIncludeInRelease
 %<*2ekernel>
 %    \end{macrocode}
 %  \end{macro}
+%  \end{macro}
+%  \end{macro}
 %
 %
 %