Fixed pipe tables -- headerless tables are not allowed.

GFM and PHP Markdown Extra pipe tables require headers.
Previously pandoc allowed pipe tables not to include headers,
and produced headerless pipe tables in Markdown output, but this
was based on a misconception about pipe table syntax. This
commit fixes this.

Note:  If you have been using headerless pipe tables, this may
cause existing tables to break.

Closes #1996.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index 910936b34..fcd18fdc0 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -1287,11 +1287,9 @@ pipeBreak = try $ do
 
 pipeTable :: MarkdownParser ([Alignment], [Double], F [Blocks], F [[Blocks]])
 pipeTable = try $ do
-  (heads,aligns) <- try ( pipeBreak >>= \als ->
-                     return (return $ replicate (length als) mempty, als))
-                  <|> ( pipeTableRow >>= \row -> pipeBreak >>= \als ->
-
-                          return (row, als) )
+  (heads,aligns) <- pipeTableRow >>= \row ->
+                    pipeBreak >>= \als ->
+                    return (row, als)
   lines' <- sequence <$> many1 pipeTableRow
   let widths = replicate (length aligns) 0.0
   return $ (aligns, widths, heads, lines')