table-short-captions: fix support for Pandod 2.10+

Commit 6e1b2cc (table-short-captions: add support for pandoc 2.10,
2020-07-15) doesn't work because it treats the new `Table.caption.long`
object as the pre 2.10 `Table.caption` object, but they are completely
different lists. `Table.caption.long` is a list of `Blocks`, where each
block has a `content` key which is a `List` of inlines (or it should be,
a test would be needed for more complex captions?). The pre 2.10
`Table.caption` is a `List` of inlines, so they cannot share the same
code to be manipulated.

Fix by just splitting into two different functions. They do follow the
same structure, but it is better to keep them separated, otherwise it
would require too many ifs, or code that is not clear.

For pre 2.10 `Table.caption` just keep the code as it is.
For the new `Table.caption.long`, ensure that the outer list of `Blocks`
is taken into account when searching for the inline `Span` with the
short caption.

Now all tests pass again.

Author: smancill

table-short-captions/table-short-captions.lua

@@ -92,27 +92,24 @@ local function parse_table_attrs(attr)
   return label, short_caption, unlisted
 end
 
---- Wraps a table with shortcaption code
+function is_properties_span(inl)
+  return (inl.t) and (inl.t == "Span")                      -- is span
+                 and (inl.content) and (#inl.content == 0)  -- is empty span
+end
+
+--- Parse the caption for Pandoc < 2.10
 -- @tparam Table tbl : The table with {}-wrapped properties in the caption
--- @treturn List[Blocks] : The table with {label} in the caption,
---                         optionally wrapped in shortcaption code
-function rewrite_longtable_caption(tbl)
-  local caption
-  if PANDOC_VERSION >= {2,10} then
-    caption = pandoc.List(tbl.caption.long)
-  else
-    caption = tbl.caption
-  end
+-- @treturn ?string : The "short-caption" property, if present.
+-- @treturn bool : Whether ".unlisted" appeared in the classes
+function parse_short_caption_legacy(tbl)
+  local caption = tbl.caption
+
   -- Escape if there is no caption present.
   if not caption or #caption == 0 then
     return nil
   end
 
   -- Try find the properties block
-  local is_properties_span = function (inl)
-    return (inl.t) and (inl.t == "Span")                      -- is span
-                   and (inl.content) and (#inl.content == 0)  -- is empty span
-  end
   local propspan, idx = caption:find_if(is_properties_span)
 
   -- If we couldn't find properties, escape.
@@ -132,13 +129,69 @@ function rewrite_longtable_caption(tbl)
   end
 
   -- set new caption
+  tbl.caption = caption
+
+  return short_caption, unlisted
+end
+
+--- Parse the caption for Pandoc >= 2.10
+-- @tparam Table tbl : The table with {}-wrapped properties in the caption
+-- @treturn ?string : The "short-caption" property, if present.
+-- @treturn bool : Whether ".unlisted" appeared in the classes
+function parse_short_caption(tbl)
+  local caption = pandoc.List(tbl.caption.long)
+
+  -- Escape if there is no caption present.
+  if #caption == 0 then
+    return nil
+  end
+
+  -- Try find the properties block
+  local find_properties = function (list)
+    for bidx, block in ipairs(list) do
+      local propspan, idx = block.content:find_if(is_properties_span)
+      if propspan then
+        return propspan, bidx, idx
+      end
+    end
+  end
+  local propspan, bidx, idx = find_properties(caption)
+
+  -- If we couldn't find properties, escape.
+  if not propspan then
+    return nil
+  end
+
+  -- Otherwise, parse it all
+  local label, short_caption, unlisted = parse_table_attrs(propspan.attr)
+
+  -- Excise the span from the caption
+  caption[bidx].content[idx] = nil
+
+  -- Put label back into caption for pandoc-crossref
+  if label then
+    caption[bidx].content:extend {pandoc.Str("{#"..label.."}")}
+  end
+
+  -- set new caption
+  tbl.caption.long = caption
+  tbl.caption.short = short_caption
+    and pandoc.read(short_caption, FORMAT).blocks[1].content
+    or nil
+
+  return short_caption, unlisted
+end
+
+--- Wraps a table with shortcaption code
+-- @tparam Table tbl : The table with {}-wrapped properties in the caption
+-- @treturn List[Blocks] : The table with {label} in the caption,
+--                         optionally wrapped in shortcaption code
+function rewrite_longtable_caption(tbl)
+  local short_caption, unlisted
   if PANDOC_VERSION >= {2,10} then
-    tbl.caption.long = caption
-    tbl.caption.short = short_caption
-      and pandoc.read(short_caption, FORMAT).blocks[1].content
-      or nil
+    short_caption, unlisted = parse_short_caption(tbl)
   else
-    tbl.caption = caption
+    short_caption, unlisted = parse_short_caption_legacy(tbl)
   end
 
   -- Place new table