Use the new builders, modify readers to preserve empty headers

The Builder.simpleTable now only adds a row to the TableHead when the
given header row is not null. This uncovered an inconsistency in the
readers: some would unconditionally emit a header filled with empty
cells, even if the header was not present. Now every reader has the
conditional behaviour. Only the XWiki writer depended on the header
row being always present; it now pads its head as necessary.

4 files changed, 5 insertions, 5 deletions

diff --git a/src/Text/Pandoc/Writers/Docbook.hs b/src/Text/Pandoc/Writers/Docbook.hs
index ba468cf4f..2f033b19e 100644
--- a/src/Text/Pandoc/Writers/Docbook.hs
+++ b/src/Text/Pandoc/Writers/Docbook.hs
@@ -280,7 +280,7 @@ blockToDocbook opts (Table _ blkCapt specs thead tbody tfoot) = do
   body' <- (inTagsIndented "tbody" . vcat) <$>
               mapM (tableRowToDocbook opts) rows
   return $ inTagsIndented tableType $ captionDoc $$
-        inTags True "tgroup" [("cols", tshow (length headers))] (
+        inTags True "tgroup" [("cols", tshow (length aligns))] (
          coltags $$ head' $$ body')
 
 hasLineBreaks :: [Inline] -> Bool
diff --git a/src/Text/Pandoc/Writers/FB2.hs b/src/Text/Pandoc/Writers/FB2.hs
index 83bcf2038..5e6f1861e 100644
--- a/src/Text/Pandoc/Writers/FB2.hs
+++ b/src/Text/Pandoc/Writers/FB2.hs
@@ -336,10 +336,10 @@ blockToXml h@Header{} = do
 blockToXml HorizontalRule = return [ el "empty-line" () ]
 blockToXml (Table _ blkCapt specs thead tbody tfoot) = do
     let (caption, aligns, _, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
-    hd <- mkrow "th" headers aligns
+    hd <- if null headers then pure [] else (:[]) <$> mkrow "th" headers aligns
     bd <- mapM (\r -> mkrow "td" r aligns) rows
     c <- el "emphasis" <$> cMapM toXml caption
-    return [el "table" (hd : bd), el "p" c]
+    return [el "table" (hd <> bd), el "p" c]
     where
       mkrow :: PandocMonad m => String -> [[Block]] -> [Alignment] -> FBM m Content
       mkrow tag cells aligns' =
diff --git a/src/Text/Pandoc/Writers/TEI.hs b/src/Text/Pandoc/Writers/TEI.hs
index f7fa19b1b..9ccc137eb 100644
--- a/src/Text/Pandoc/Writers/TEI.hs
+++ b/src/Text/Pandoc/Writers/TEI.hs
@@ -196,7 +196,7 @@ blockToTEI _ HorizontalRule = return $
 -- table info in the AST is here lossily discard.
 blockToTEI opts (Table _ blkCapt specs thead tbody tfoot) = do
   let (_, _, _, headers, rows) = toLegacyTable blkCapt specs thead tbody tfoot
-  headers' <- tableHeadersToTEI opts headers
+  headers' <- if null headers then pure mempty else tableHeadersToTEI opts headers
   rows' <- mapM (tableRowToTEI opts) rows
   return $ inTags True "table" [] $ headers' $$ vcat rows'
 
diff --git a/src/Text/Pandoc/Writers/XWiki.hs b/src/Text/Pandoc/Writers/XWiki.hs
index bfc61c3b5..486de943f 100644
--- a/src/Text/Pandoc/Writers/XWiki.hs
+++ b/src/Text/Pandoc/Writers/XWiki.hs
@@ -125,7 +125,7 @@ blockToXWiki (DefinitionList items) = do
 -- TODO: support more features
 blockToXWiki (Table _ blkCapt specs thead tbody tfoot) = do
   let (_, _, _, headers, rows') = toLegacyTable blkCapt specs thead tbody tfoot
-  headers' <- mapM (tableCellXWiki True) headers
+  headers' <- mapM (tableCellXWiki True) $ take (length specs) $ headers ++ repeat []
   otherRows <- mapM formRow rows'
   return $ Text.unlines (Text.unwords headers':otherRows)