[latex3-commits] [git/LaTeX3-latex3-latex2e] develop: Don't return true in LuaTeX list callbacks (c0381814)

[Marcel Fabian Krüger]

Repository : https://github.com/latex3/latex2e
On branch  : develop
Link       : https://github.com/latex3/latex2e/commit/c038181414defe3b335380cc9521f2c692bd8012

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

commit c038181414defe3b335380cc9521f2c692bd8012
Author: Marcel Fabian Krüger <tex at 2krueger.de>
Date:   Mon Nov 8 09:17:07 2021 +0100

    Don't return true in LuaTeX list callbacks


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

c038181414defe3b335380cc9521f2c692bd8012
 base/changes.txt                           |  1 +
 base/doc/ltnews35.tex                      |  5 +++++
 base/ltluatex.dtx                          | 19 ++++++-------------
 base/ltshipout.dtx                         |  5 +++--
 base/testfiles/tlb-ltluatex-001.luatex.tlg |  2 +-
 5 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/base/changes.txt b/base/changes.txt
index e4391479..79d9ec7e 100644
--- a/base/changes.txt
+++ b/base/changes.txt
@@ -10,6 +10,7 @@ are not part of the distribution.
 
 	* ltluatex.dtx:
 	Classify [hv]pack_quality callbacks as exclusive
+	Never pass true to the engine for LuaTeX list callbacks
 
 ================================================================================
 All changes above are only part of the development branch for the next release.
diff --git a/base/doc/ltnews35.tex b/base/doc/ltnews35.tex
index b701339a..6b5d4816 100644
--- a/base/doc/ltnews35.tex
+++ b/base/doc/ltnews35.tex
@@ -155,6 +155,11 @@ The previous type \texttt{list} resulted in incorrect parameters when multiple
 handlers were set, therefore this only makes an existing restriction more
 explicit.
 
+Additionally the return value \texttt{true} for \texttt{list} callbacks is now
+handled internally and no longer passed on to the engine. This simplifies the
+handling of these callbacks and makes it easier to provide consistent
+interfaces for user defined \texttt{list} callbacks.
+
 \subsection{???}
 %
 \githubissue{???}
diff --git a/base/ltluatex.dtx b/base/ltluatex.dtx
index 1f8598ff..612e1354 100644
--- a/base/ltluatex.dtx
+++ b/base/ltluatex.dtx
@@ -1518,11 +1518,11 @@ end
 % Handler for |list| callbacks.
 % \changes{v1.0k}{2015/12/02}{resolve name and i.description (PHG)}
 % \changes{v1.1s}{2020/12/02}{Fix return value of list callbacks}
+% \changes{v1.1w}{2021/11/17}{Never pass on \texttt{true} return values for list callbacks}
 %    \begin{macrocode}
 local function list_handler(name)
   return function(head, ...)
     local ret
-    local alltrue = true
     for _,i in ipairs(callbacklist[name]) do
       ret = i.func(head, ...)
       if ret == false then
@@ -1533,18 +1533,17 @@ local function list_handler(name)
         return false
       end
       if ret ~= true then
-        alltrue = false
         head = ret
       end
     end
-    return alltrue and true or head
+    return head
   end
 end
 %    \end{macrocode}
 % Default for user-defined |list| and |reverselist| callbacks without explicit default.
 %    \begin{macrocode}
-local function list_handler_default()
-  return true
+local function list_handler_default(head)
+return head
 end
 %    \end{macrocode}
 % Handler for |reverselist| callbacks.
@@ -1553,7 +1552,6 @@ end
 local function reverselist_handler(name)
   return function(head, ...)
     local ret
-    local alltrue = true
     local callbacks = callbacklist[name]
     for i = #callbacks, 1, -1 do
       local cb = callbacks[i]
@@ -1566,11 +1564,10 @@ local function reverselist_handler(name)
         return false
       end
       if ret ~= true then
-        alltrue = false
         head = ret
       end
     end
-    return alltrue and true or head
+    return head
   end
 end
 %    \end{macrocode}
@@ -1901,14 +1898,10 @@ callback_register("mlist_to_hlist", function(head, display_type, need_penalties)
   if current == false then
     flush_list(head)
     return nil
-  elseif current == true then
-    current = head
   end
   current = call_callback("mlist_to_hlist", current, display_type, need_penalties)
   local post = call_callback("post_mlist_to_hlist_filter", current, display_type, need_penalties)
-  if post == true then
-    return current
-  elseif post == false then
+  if post == false then
     flush_list(current)
     return nil
   end
diff --git a/base/ltshipout.dtx b/base/ltshipout.dtx
index 7f6555d1..9e7bf4be 100644
--- a/base/ltshipout.dtx
+++ b/base/ltshipout.dtx
@@ -741,8 +741,9 @@
         luatexbase.create_callback('pre_shipout_filter', 'list')
         local~call, getbox, setbox = luatexbase.call_callback, tex.getbox, tex.setbox~
         lua.get_functions_table()[\the \@@_finalize_box:] = function()
-          local~result = call('pre_shipout_filter', getbox(\the \l_shipout_box))
-          if~not (result == true) then~
+          local head = getbox(\the \l_shipout_box)
+          local~result = call('pre_shipout_filter', head)
+          if~not (result == head) then~
             setbox(\the \l_shipout_box, result~or~nil)
           end~
         end
diff --git a/base/testfiles/tlb-ltluatex-001.luatex.tlg b/base/testfiles/tlb-ltluatex-001.luatex.tlg
index 7f07f32d..53c7483d 100644
--- a/base/testfiles/tlb-ltluatex-001.luatex.tlg
+++ b/base/testfiles/tlb-ltluatex-001.luatex.tlg
@@ -7,7 +7,7 @@ stack traceback:
 ^^I[C]: in function 'error'
 ^^I./ltluatex.lua:110: in upvalue 'module_error'
 ^^I./ltluatex.lua:117: in upvalue 'luatexbase_error'
-^^I./ltluatex.lua:432: in field 'create_callback'
+^^I./ltluatex.lua:428: in field 'create_callback'
 ^^I[\directlua]:1: in main chunk.
 l. ...}
 The lua interpreter ran into a problem, so the