Loading .sta file before \AtBeginDocument

[muzimuzhi]

Currently, .sta file, which (if exists) contains the collected sub-preambles, is read at begin of document (\AtBeginDocument). Since theses preambles may load packages by themselves, loading .sta in \AtBeginDocument maybe too late. See discussions in latex3/hyperref#242 and question 670638 on TeX-SX.

In LaTeX2e 2020-10-01, a hook management system is introduced hence \AtBeginDocument becomes a thin wrapper of \AddToHook{begindocument}. This hook system also provides a better position to load packages at the end of preamble: hook begindocument/before. In older LaTeX2e, this hook can be emulated by \AtEndPreamble from etoolbox package.

A proposal that only makes code changes (comment are not adapted):

diff --git a/standalone.sty b/standalone.sty
index 557f254..497a571 100644
--- a/standalone.sty
+++ b/standalone.sty
@@ -933,7 +933,11 @@
 % The |standalone| macros are defined to be without effect. If `sorting' is enabled \cs{usepackage} is temporarily
 % redefined to ignore any given options, which where already passed (\cs{PassOptionsToPackage}) beforehand.
 %    \begin{macrocode}
-\AtBeginDocument{%
+\providecommand\IfFormatAtLeastTF{\@ifl@t@r\fmtversion}
+\IfFormatAtLeastTF{2020-10-01}
+  {\AddToHook{begindocument/before}}
+  {\RequirePackage{etoolbox}\AtEndPreamble}
+{%
   \let\subpreamble\@gobble
   \let\endsubpreamble\relax
   \let\standalonepreambles\relax

[dbitouze]

Any news about this issue?