[latex3-commits] [git/LaTeX3-latex3-latex2e] para-issue: experimental fix for strance error caused by listings redefining \vskip (91126d9e)

[Frank Mittelbach]

Repository : https://github.com/latex3/latex2e
On branch  : para-issue
Link       : https://github.com/latex3/latex2e/commit/91126d9eddd7e8dd2db43d673be16ba89be0e486

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

commit 91126d9eddd7e8dd2db43d673be16ba89be0e486
Author: Frank Mittelbach <frank.mittelbach at latex-project.org>
Date:   Sun Jun 27 19:13:03 2021 +0200

    experimental fix for strance error caused by listings redefining \vskip


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

91126d9eddd7e8dd2db43d673be16ba89be0e486
 base/ltpara.dtx                   | 28 ++++++++++++++++++++++++++--
 base/testfiles/tlb0406.luatex.tlg |  2 +-
 base/testfiles/tlb0406.tlg        |  2 +-
 base/testfiles/tlb0942.luatex.tlg |  2 +-
 base/testfiles/tlb0942.tlg        |  2 +-
 base/testfiles/tlb2558.luatex.tlg |  2 +-
 base/testfiles/tlb2558.tlg        |  2 +-
 base/testfiles/tlb2558.xetex.tlg  |  2 +-
 8 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/base/ltpara.dtx b/base/ltpara.dtx
index 5ab52a5e..5ebecffe 100644
--- a/base/ltpara.dtx
+++ b/base/ltpara.dtx
@@ -14,8 +14,8 @@
 %%% From File: ltpara.dtx
 %
 %    \begin{macrocode}
-\def\ltparaversion{v1.0g}
-\def\ltparadate{2021/05/27}
+\def\ltparaversion{v1.0h}
+\def\ltparadate{2021/06/27}
 %    \end{macrocode}
 %<*driver>
 \documentclass{l3doc}
@@ -972,6 +972,30 @@
 %    above construct but two conditionals instead. Using low-level
 %    \cs{if_mode...} conditions would be even faster but has the
 %    danger to conflict with conditionals in the user hooks.
+%  
+%    If \cs{para_end:} is executed while \TeX{} is currently doing a
+%    low-level assignment the test for horizontal mode may get
+%    executed as part of the assignment. That is normally not an issue
+%    but we just found one case where it is:
+%\begin{verbatim}
+%   \afterassignment\lst at vskip\@tempskipa \z@ \par
+%\end{verbatim}
+%    If \TeX{} is in hmode while that assignment happens then the
+%    \cs{par} is seen in hmode (because in the above case the
+%    assignment isn't finished (one should have used \cs{z at skip} and
+%    the \cs{lst at vskip} will get inserted into the middle of the
+%    conditional. The \cs{lst at vskip} then changes to vmode and you get
+%    a surprising error about the \texttt{para/end} hook having
+%    changed modes even if you don't have any hook code because it is
+%    the instered \cs{lst at vskip} that is causing it. That happened
+%    when the output routines got started while a \texttt{lstlisting}
+%    environment (that redefines \cs{vskip} in this way) was was
+%    active. This is really faulty coding, but we try to be proactive
+%    and guard the conditional so thatany scanning is stopped before it:
+%    \begin{macrocode}
+  \scan_stop:
+%    \end{macrocode}
+%    
 %    \begin{macrocode}
   \mode_if_horizontal:TF {
     \mode_if_inner:F {
diff --git a/base/testfiles/tlb0406.luatex.tlg b/base/testfiles/tlb0406.luatex.tlg
index ad3fef19..ebd0e376 100644
--- a/base/testfiles/tlb0406.luatex.tlg
+++ b/base/testfiles/tlb0406.luatex.tlg
@@ -17,5 +17,5 @@ l. ...\DeclareMathSymbol{a}{7}{operators}{`\a}
 l. ...\DeclareMathSymbol{a}{7}{letters}{`\a}
 > 31457377.
 <to be read again> 
-\tex_par:D 
+\scan_stop: 
 l. ...
diff --git a/base/testfiles/tlb0406.tlg b/base/testfiles/tlb0406.tlg
index 9f32b6aa..8569f0f1 100644
--- a/base/testfiles/tlb0406.tlg
+++ b/base/testfiles/tlb0406.tlg
@@ -17,5 +17,5 @@ l. ...\DeclareMathSymbol{a}{7}{operators}{`\a}
 l. ...\DeclareMathSymbol{a}{7}{letters}{`\a}
 > 29025.
 <to be read again> 
-                   \tex_par:D 
+                   \scan_stop: 
 l. ...
diff --git a/base/testfiles/tlb0942.luatex.tlg b/base/testfiles/tlb0942.luatex.tlg
index b1e0a6be..119e2573 100644
--- a/base/testfiles/tlb0942.luatex.tlg
+++ b/base/testfiles/tlb0942.luatex.tlg
@@ -737,5 +737,5 @@ l. ...\showthe
             \mathcode`\z
 > 31457402.
 <to be read again> 
-\tex_par:D 
+\scan_stop: 
 l. ...
diff --git a/base/testfiles/tlb0942.tlg b/base/testfiles/tlb0942.tlg
index 3ffcf8a2..7f770986 100644
--- a/base/testfiles/tlb0942.tlg
+++ b/base/testfiles/tlb0942.tlg
@@ -737,5 +737,5 @@ l. ...\showthe
               \mathcode`\z
 > 29050.
 <to be read again> 
-                   \tex_par:D 
+                   \scan_stop: 
 l. ...
diff --git a/base/testfiles/tlb2558.luatex.tlg b/base/testfiles/tlb2558.luatex.tlg
index c9e33292..22b39a06 100644
--- a/base/testfiles/tlb2558.luatex.tlg
+++ b/base/testfiles/tlb2558.luatex.tlg
@@ -25,7 +25,7 @@ For xelatex or lualatex save the document in UTF-8 encoding
 and do not use inputenc, or use the [utf8] option.
 > 11.
 <to be read again> 
-\tex_par:D 
+\scan_stop: 
 l. ...
 ! Package inputenc Error: inputenc is not designed for xetex or luatex.
 (inputenc)                only UTF-8 supported.
diff --git a/base/testfiles/tlb2558.tlg b/base/testfiles/tlb2558.tlg
index 4a72c80b..ff25753e 100644
--- a/base/testfiles/tlb2558.tlg
+++ b/base/testfiles/tlb2558.tlg
@@ -20,7 +20,7 @@ File: latin1.def ....-..-.. v... Input encoding file
 )
 > 11.
 <to be read again> 
-                   \tex_par:D 
+                   \scan_stop: 
 l. ...
 > 12.
 l. ...\showthe\catcode`\@ 
diff --git a/base/testfiles/tlb2558.xetex.tlg b/base/testfiles/tlb2558.xetex.tlg
index c4c9554e..6aa88e2c 100644
--- a/base/testfiles/tlb2558.xetex.tlg
+++ b/base/testfiles/tlb2558.xetex.tlg
@@ -25,7 +25,7 @@ For xelatex or lualatex save the document in UTF-8 encoding
 and do not use inputenc, or use the [utf8] option.
 > 11.
 <to be read again> 
-                   \tex_par:D 
+                   \scan_stop: 
 l. ...
 ! Package inputenc Error: inputenc is not designed for xetex or luatex.
 (inputenc)                only UTF-8 supported.