hierarchicalize: Do not number section with class "unnumbered".

Unnumbered sections get [] for their section number.
So far only the HTML writer has been adjusted to be sensitive
to this.

If we keep this change, all the writers will need to be changed
either (a) to directly check for the "unnumbered" class, if they
do section numbering themselves, or (b) to check for a null section
number, if they use hierarchicalize.

src/Text/Pandoc/Shared.hs

@@ -92,7 +92,7 @@ import Text.Pandoc.MIME (getMimeType)
 import System.FilePath ( (</>), takeExtension, dropExtension )
 import Data.Generics (Typeable, Data)
 import qualified Control.Monad.State as S
-import Control.Monad (msum)
+import Control.Monad (msum, unless)
 import Text.Pandoc.Pretty (charWidth)
 import System.Locale (defaultTimeLocale)
 import Data.Time
@@ -435,13 +435,15 @@ hierarchicalize blocks = S.evalState (hierarchicalizeWithIds blocks) []
 
 hierarchicalizeWithIds :: [Block] -> S.State [Int] [Element]
 hierarchicalizeWithIds [] = return []
-hierarchicalizeWithIds ((Header level attr title'):xs) = do
+hierarchicalizeWithIds ((Header level attr@(_,classes,_) title'):xs) = do
   lastnum <- S.get
   let lastnum' = take level lastnum
-  let newnum = if length lastnum' >= level
-                  then init lastnum' ++ [last lastnum' + 1]
-                  else lastnum ++ replicate (level - length lastnum - 1) 0 ++ [1]
-  S.put newnum
+  let newnum = case length lastnum' of
+                    x | "unnumbered" `elem` classes -> []
+                      | x >= level -> init lastnum' ++ [last lastnum' + 1]
+                      | otherwise -> lastnum ++
+                           replicate (level - length lastnum - 1) 0 ++ [1]
+  unless (null newnum) $ S.put newnum
   let (sectionContents, rest) = break (headerLtEq level) xs
   sectionContents' <- hierarchicalizeWithIds sectionContents
   rest' <- hierarchicalizeWithIds rest

src/Text/Pandoc/Writers/HTML.hs

@@ -252,9 +252,9 @@ showSecNum = concat . intersperse "." . map show
 elementToListItem :: WriterOptions -> Element -> State WriterState (Maybe Html)
 elementToListItem opts (Sec lev num (id',classes,keyvals) headerText subsecs)
   | lev <= writerTOCDepth opts = do
-  let sectnum = if writerNumberSections opts
-                   then (H.span ! A.class_ "toc-section-number" $ toHtml $ showSecNum num) >>
-                     preEscapedString " "
+  let sectnum = if writerNumberSections opts && not (null num)
+                   then (H.span ! A.class_ "toc-section-number"
+                        $ toHtml $ showSecNum num) >> preEscapedString " "
                    else mempty
   txt <- liftM (sectnum >>) $ inlineListToHtml opts headerText
   subHeads <- mapM (elementToListItem opts) subsecs >>= return . catMaybes
@@ -453,9 +453,9 @@ blockToHtml opts (BlockQuote blocks) =
 blockToHtml opts (Header level (ident,_,_) lst) = do
   contents <- inlineListToHtml opts lst
   secnum <- liftM stSecNum get
-  let contents' = if writerNumberSections opts
-                     then (H.span ! A.class_ "header-section-number" $ toHtml $ showSecNum secnum) >>
-                            strToHtml " " >> contents
+  let contents' = if writerNumberSections opts && not (null secnum)
+                     then (H.span ! A.class_ "header-section-number" $ toHtml
+                          $ showSecNum secnum) >> strToHtml " " >> contents
                      else contents
   let contents''  = if writerTableOfContents opts && not (null ident)
                        then H.a ! A.href (toValue $