Adapt to Pandoc 2.17 changes

[Christophe Dervieux]

There was a big change in Lua for Pandoc regarding how meta values are treated.
https://pandoc.org/releases.html#pandoc-2.17-2022-01-12

Elements of type MetaValue are no longer pushed as values which have .t and .tag properties. This was already true for MetaString and MetaBool values, which are still marshaled as Lua strings and booleans, respectively. Affected values:

MetaBlocks values are marshaled as a Blocks list;
MetaInlines values are marshaled as a Inlines list;
MetaList values are marshaled as a generic pandoc Lists.
MetaMap values are marshaled as plain tables and no longer given any metatable.

We probably need to adjust some of our filters like

pagedown/inst/resources/lua/jss.lua

Lines 50 to 98 in 7ed2764

 Meta = function(meta) 
   --------------------------------------- 
   --           Keywords                -- 
   --------------------------------------- 
   -- Test if there is one keyword: 
   if not meta.keywords then error("At least one keyword must be supplied.") end 
   -- Store plain keywords: 
   local plainKeywords = {} 
  
   if meta.keywords.t == "MetaList" then 
     for i, v in ipairs(meta.keywords) do 
       plainKeywords[i] = pandoc.utils.stringify(v) 
     end 
   else 
     -- we have only one keyword 
     plainKeywords = {pandoc.utils.stringify(meta.keywords)} 
   end 
  
   meta["keywords-plain"] = plainKeywords 
  
   --------------------------------------- 
   --              Author               -- 
   --------------------------------------- 
   local author = meta.author 
  
   if author.t == "MetaInlines" then 
     meta.author = {data = author, rank = "1"} 
   else 
     for i, v in ipairs(author) do 
       meta.author[i] = {data = v, rank = tostring(i)} 
     end 
   end 
  
   ---------------------------------------- 
   --  Build DOI from volume and issue   -- 
   ---------------------------------------- 
   meta.doi = getDOI(meta.volume, meta.issue) 
  
   ---------------------------------------- 
   -- Fallback values for missing params -- 
   ---------------------------------------- 
   if not meta.month then meta.month = "MMMMMM" end 
   if not meta.year then meta.year = "YYYY" end 
   if not meta.volume then meta.volume = "VV" end 
   if not meta.issue then meta.issue = "II" end 
   if not meta.submitdate then meta.submitdate = "yyyy-mm-dd" end 
   if not meta.acceptdate then meta.acceptdate = "yyyy-mm-dd" end 
  
   return meta 

.t no more exist and type must be checked using

pandoc.utils.type(meta.keywords) == "List"

This will work only for Pandoc 2.17 so we need to adjust to use several syntax depending on the Pandoc version probably to not break existing code and not set a hard requirement on Pandoc 2.17

Note that no error is thrown (nothing in CI even following #267) so this will silently have side effect with the Lua filter not applying as it should

[Christophe Dervieux]

Seems like we don't need to test the type in fact. This would help the filter to work with any version of Pandoc

diff --git a/inst/resources/lua/jss.lua b/inst/resources/lua/jss.lua
index ee8f841..70791aa 100644
--- a/inst/resources/lua/jss.lua
+++ b/inst/resources/lua/jss.lua
@@ -56,13 +56,8 @@ Meta = function(meta)
   -- Store plain keywords:
   local plainKeywords = {}

-  if meta.keywords.t == "MetaList" then
-    for i, v in ipairs(meta.keywords) do
-      plainKeywords[i] = pandoc.utils.stringify(v)
-    end
-  else
-    -- we have only one keyword
-    plainKeywords = {pandoc.utils.stringify(meta.keywords)}
+  for i, v in ipairs(meta.keywords) do
+    plainKeywords[i] = pandoc.utils.stringify(v)
   end

   meta["keywords-plain"] = plainKeywords
@@ -72,12 +67,8 @@ Meta = function(meta)
   ---------------------------------------
   local author = meta.author

-  if author.t == "MetaInlines" then
-    meta.author = {data = author, rank = "1"}
-  else
-    for i, v in ipairs(author) do
-      meta.author[i] = {data = v, rank = tostring(i)}
-    end
+  for i, v in ipairs(author) do
+    meta.author[i] = {data = v, rank = tostring(i)}
   end

@RLesur how does it looks ?

I don't see where to check the difference between MetaInlines and MetaList effect. The template uses for loops which seems to account for the two type 🤔

[Christophe Dervieux]

Ok I found why

author: Yihui Xie

One author in YAML will trigger the error when using 2.17