Docx reader: Ensure one-row tables don't have header.

Tables in MS Word are set by default to have special first-row
formatting, which pandoc uses to determine whether or not they have a
header. This means that one-row tables will, by default, have only a
header -- which we imagine is not what people want. This change
ensures that a one-row table is not understood to be a header only.

Note that this means that it is impossible to produce a header-only
table from docx, even though it is legal pandoc. But we believe that
in nearly all cases, it will be an accidental (and unwelcome) result

Closes #3285.

src/Text/Pandoc/Readers/Docx.hs

@@ -568,7 +568,8 @@ bodyPartToBlocks (Tbl _ _ _ []) =
 bodyPartToBlocks (Tbl cap _ look (r:rs)) = do
   let caption = text cap
       (hdr, rows) = case firstRowFormatting look of
-        True -> (Just r, rs)
+        True | null rs -> (Nothing, [r])
+             | otherwise -> (Just r, rs)
         False -> (Nothing, r:rs)
   hdrCells <- case hdr of
     Just r' -> rowToBlocksList r'

tests/Tests/Readers/Docx.hs

@@ -241,6 +241,10 @@ tests = [ testGroup "inlines"
             "tables with lists in cells"
             "docx/table_with_list_cell.docx"
             "docx/table_with_list_cell.native"
+          , testCompare
+            "tables with one row"
+            "docx/table_one_row.docx"
+            "docx/table_one_row.native"
           , testCompare
             "code block"
             "docx/codeblock.docx"

tests/docx/table_one_row.native

@@ -0,0 +1,5 @@
+[Table [] [AlignDefault,AlignDefault,AlignDefault] [0.0,0.0,0.0]
+ []
+ [[[Plain [Str "One"]]
+  ,[Plain [Str "Row"]]
+  ,[Plain [Str "Table"]]]]]