[latex3-commits] [git/LaTeX3-latex3-latex2e] gh239: Add ltnews entry for \DeclareCommandCopy (597594fe)

[PhelypeOleinik]

Repository : https://github.com/latex3/latex2e
On branch  : gh239
Link       : https://github.com/latex3/latex2e/commit/597594fe0e366b46f8d12746d85cb11bec4fccae

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

commit 597594fe0e366b46f8d12746d85cb11bec4fccae
Author: PhelypeOleinik <tex.phelype at gmail.com>
Date:   Sat May 9 00:35:27 2020 -0300

    Add ltnews entry for \DeclareCommandCopy


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

597594fe0e366b46f8d12746d85cb11bec4fccae
 base/doc/ltnews32.tex | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/base/doc/ltnews32.tex b/base/doc/ltnews32.tex
index b04f2d03..b902d70c 100644
--- a/base/doc/ltnews32.tex
+++ b/base/doc/ltnews32.tex
@@ -386,6 +386,46 @@ are ignored as elsewhere.
 \githubissue{327}
 
 
+\subsection{Provide a way to copy commands}
+
+With the previous \LaTeXe{} release, several user-level commands were
+made robust, so the need for a way to create copies of these commands
+(often to redefine them) increased, and the \LaTeXe{} kernel didn't have
+a way to do so.  Previously this functionality was provided in part by
+Heiko Oberdiek's \pkg{letltxmacro} package, which allows a robust
+command \verb=\foo= to be copied to \verb=\bar= with
+\verb=\LetLtxMacro\bar\foo=.
+
+From this release onwards, the \LaTeXe{} kernel provides
+\cs{NewCommandCopy} (and \verb=\Renew...=, \verb=\Declare...=, and
+\verb=\Provide...= variants) which functions almost like
+\verb=\LetLtxMacro=.  To the end user, both should work the same way,
+and one shouldn't need to worry about the definition of the command:
+\cs{NewCommandCopy} should do the hard work.
+
+For developers, lower level macros \cs{CopyKernelRobustCommand} and
+\cs{CopyKernelCmdWithOptArg} are provided to copy commands defined with
+\cs{DeclareRobustCommand} and commands defined with an optional
+argument, respectively.  Conditionals \cs{IfKernelRobustCommand} and
+\cs{IfKernelCmdWithOptArg} are provided to check these cases if
+necessary.  These macros are faster than the generic \cs{NewCommandCopy}
+because they don't have to test for all possibilities.
+
+Also, at an even lower level, developers can add their own types of
+macros to the list of tests done by \cs{NewCommandCopy}.  A hook
+\cs{@declarecommandcopylisthook} whose items are pair of control
+sequences which test if a macro is of a given type, and copy that type
+of macro.  For instance, \pkg{etoolbox} provides a different type of
+robust command defined with \cs{newrobustcmd}.  This can be added to the
+list of tests with:
+\begin{verbatim}
+\g at addto@macro\@declarecommandcopylisthook
+  {\ifrobustcmd\letrobustcmd}
+\end{verbatim}
+then \cs{NewCommandCopy} will support macros defined with
+\cs{newrobustcmd}.
+
+\githubissue{239}
 
 
 \section{Changes to packages in the \pkg{graphics} category}