[latex3-commits] [git/LaTeX3-latex3-latex3] cmd: Rework loading logic (f504988df)

[PhelypeOleinik]

Repository : https://github.com/latex3/latex3
On branch  : cmd
Link       : https://github.com/latex3/latex3/commit/f504988df439eb131f8697d05a8a6c8f5c00ecb4

>---------------------------------------------------------------

commit f504988df439eb131f8697d05a8a6c8f5c00ecb4
Author: PhelypeOleinik <phelype.oleinik at latex-project.org>
Date:   Sat Jan 23 16:25:30 2021 -0300

    Rework loading logic


>---------------------------------------------------------------

f504988df439eb131f8697d05a8a6c8f5c00ecb4
 l3packages/xparse/xparse.dtx | 80 +++++++++++++++++++++++++++++++-------------
 1 file changed, 57 insertions(+), 23 deletions(-)

diff --git a/l3packages/xparse/xparse.dtx b/l3packages/xparse/xparse.dtx
index d0c0af090..506146365 100644
--- a/l3packages/xparse/xparse.dtx
+++ b/l3packages/xparse/xparse.dtx
@@ -969,30 +969,64 @@
 %
 % \section{\pkg{xparse} implementation}
 %
-% Three releases are declared using the rollback mechanism:
-% \begin{description}
-% \item[2018-04-12]
-%   contains the full (|package|+|core|) code for \pkg{xparse} as it was
-%   before the |core| part was integrated into \LaTeXe.  This version
-%   should be loaded if \pkg{xparse} is not loaded at all (that is, in
-%   \LaTeXe{} older than 2020-10-01);
-% \item[2020-10-01]
-%   contains only the deprecated types (|package|) for \pkg{xparse},
-%   after the |core| was integrated into \LaTeXe, and a line to load
-%   |xparse-generic.tex|.
-% \item[2021-05-01] (or later)
-%   contains roughly the same code as |2020-10-01|, except the
-%   \pkg{expl3} prefix is now |cmd|, and it doesn't try to load
-%   |xparse-generic.tex|.  This version is just an extension package for
-%   \pkg{ltcmd} in the \LaTeXe{} kernel.
-% \end{description}
-% and one of them is loaded if rolling backwards or forwards.
 %    \begin{macrocode}
-\providecommand\DeclareRelease[3]{}
-\providecommand\DeclareCurrentRelease[2]{}
-\DeclareRelease{}{2018-04-12}{xparse-2018-04-12.sty}
-\DeclareRelease{}{2020-10-01}{xparse-2020-10-01.sty}
-\DeclareCurrentRelease{}{2021-05-01}
+%<*2ekernel|package>
+%    \end{macrocode}
+%
+% This package file, along with the frozen versions in
+% \pkg{xparse-2018-04-12}, \pkg{xparse-2020-10-01}, and
+% |xparse-generic.tex|, is intended to work across different \LaTeX{}
+% releases, respected the minimum \pkg{expl3} version required by
+% \pkg{xparse}.
+%
+% We can't use the \pkg{latexrelease} mechanism with \cs{DeclareRelease}
+% here because cases of rolling forwards or backwards differ, due to the
+% prefix change from |xparse| to |cmd|, so we do our own checks to
+% ensure the right version is loaded.
+%
+% All this loading assumes that if \pkg{latexrelease} should be loaded,
+% it is before \pkg{xparse}.  The other way around was not tested at all
+% and is likely to break.
+%
+% In releases prior to 2020-10-01, \cs{NewDocumentCommand} is undefined,
+% so \pkg{xparse} was not loaded, thus we can load the full version from
+% \pkg{xparse-2018-04-12}.  Otherwise we will load only the deprecated
+% argument types from \pkg{xparse-2020-10-01}.  If we're in |2ekernel|
+% mode, it means rolling forward so load only the code code from
+% |xparse-generic.tex|.
+%    \begin{macrocode}
+\providecommand\IfFormatAtLeastTF{\@ifl at t@r\fmtversion}
+\@ifundefined{NewDocumentCommand}
+  {%
+    \IfFormatAtLeastTF{2020/10/01}
+%<2ekernel>      {\@@input xparse-generic.tex }
+%<package>      {\RequirePackage{xparse-2020-10-01}}
+      {\RequirePackage{xparse-2018-04-12}}
+    \endinput
+  }%
+%    \begin{macrocode}
+%
+% In case \cs{NewDocumentCommand} is already defined, we're either in
+% \LaTeX{} 2020-10-01 or later.  In the former case, the code loaded in
+% the kernel has the |__xparse| prefix, so we'll load
+% \pkg{xparse-2020-10-01}, otherwise we'll continue in |xparse.sty|,
+% which contains the final remains of \pkg{xparse} with the |__cmd|
+% prefix.
+%    \end{macrocode}
+  {%
+    \ifnum
+        \ifdefined\sourceLaTeXdate \sourceLaTeXdate
+        \else \expandafter\@parse at version\fmtversion//00\@nil \fi
+        = \@parse at version 2021-05-01//00\@nil
+      \expandafter\@gobblethree
+    \fi
+    \RequirePackage{xparse-2020-10-01}
+    \endinput
+  }%
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</2ekernel|package>
 %    \end{macrocode}
 %
 % In older releases, the prefix was |xparse|, but since the 2021 Spring