Fix cmd type detection

fixes #795

Author: PhelypeOleinik

base/changes.txt

@@ -6,6 +6,11 @@ completeness or accuracy and it contains some references to files that
 are not part of the distribution.
 ================================================================================
 
+2022-03-18  Phelype Oleinik  <phelype.oleinik@latex-project.org>
+
+	* ltcmd.dtx (subsection{Utilities}):
+	Fix \@@_cmd_type_cases:NnnnnF prematurely expanding macros (gh/795).
+
 2022-03-18  Joseph Wright  <joseph.wright@latex-project.org>
 
 	* ltkeys.dtx:

base/doc/ltnews35.tex

@@ -603,6 +603,16 @@ \subsection{Make \cs{cite}\texttt{\textbraceleft\textbraceright} produce a warni
 
 
 
+\subsection{Fix adding \hook{cmd} hooks to simple macros}
+
+A bug in how \LaTeX{} would detect the type of a command was causing a
+premature forced expansion of such commands, which, depending on their
+definition, could be harmless or could cause severe trouble.  This has
+been fixed in the latest release.
+%
+\githubissue{795}
+\sxissue{q/637565}
+
 
 \section{Changes to packages in the \pkg{amsmath} category}
 

base/ltcmd.dtx

@@ -34,8 +34,8 @@
 %%% From File: ltcmd.dtx
 %
 %    \begin{macrocode}
-\def\ltcmdversion{v1.0k}
-\def\ltcmddate{2022-02-28}
+\def\ltcmdversion{v1.0l}
+\def\ltcmddate{2022-03-18}
 %    \end{macrocode}
 %
 %<*driver>
@@ -4097,8 +4097,10 @@
 % \begin{macro}{\@@_cmd_type_cases:Nnnnn}
 % \changes{v1.0d}{2021/04/19}{Renamed \cs{__cmd_cmd_if_xparse:NTF} to
 %      \cs{__kernel_cmd_if_xparse:NTF} for cross-module usage}
-% \changes{v1.0d}{2021/07/30}{Added \cs{@@_cmd_type_cases:Nnnnn} for
+% \changes{v1.0d}{2021/07/30}{Added \cs{@@_cmd_type_cases:NnnnnF} for
 %      \cs{NewCommandCopy} and \cs{ShowCommand} support}
+% \changes{v1.0l}{2022/03/18}{Fix \cs{@@_cmd_type_cases:NnnnnF}
+%"     prematurely expanding macros (gh/795)}
 % \begin{macro}{\@@_cmd_if_xparse_aux:N}
 %
 %    To determine whether the command is an \pkg{xparse} command check
@@ -4119,20 +4121,15 @@
         \exp_args:Nf \tl_if_empty:nT { \cs_argument_spec:N #1 }
           {
             \token_if_macro:NT #1
-              {
-                \exp_after:wN \exp_after:wN
-                \exp_after:wN \token_to_str:N
-                \exp_after:wN \use_i_delimit_by_q_stop:nw
-                  #1 \scan_stop: \q_stop
-              }
+              { \exp_not:N \exp_not:N \exp_not:e { \tl_head:N #1 } }
           }
       }
       {
-        { \token_to_str:N \@@_start:nNNnnn } {#2}
-        { \token_to_str:N \@@_start_expandable:nNNNNn } {#3}
-        { \token_to_str:N \@@_start_env:nnnnn } {#4}
+        { \exp_not:N \@@_start:nNNnnn } {#2}
+        { \exp_not:N \@@_start_expandable:nNNNNn } {#3}
+        { \exp_not:N \@@_start_env:nnnnn } {#4}
         {
-          \exp_after:wN \token_to_str:N
+          \exp_after:wN \exp_not:N
             \cs:w environment~
               \exp_last_unbraced:Ne \use_none:nnn
                 { \cs_to_str:N #1 } ~end~aux \cs_end:

base/testfiles/github-0795.lvt

@@ -0,0 +1,8 @@
+\input test2e
+\START
+\def\test{\typeout{test}\fi}
+\AddToHook{cmd/test/after}{\typeout{hello}}
+\@kernel@after@begindocument
+\if11 % \fi comes from \test
+\test
+\END

base/testfiles/github-0795.tlg

@@ -0,0 +1,4 @@
+This is a generated file for the LaTeX2e validation system.
+Don't change this file in any respect.
+test
+hello