Shared: `makeSections` behavior changes.

+ When the optional base level parameter is provided, we no
  longer ensure that the sequence of heading levels is gapless
  [behavior change]. Instead, we set the lowest heading level to
  the specified base level, and adjust the others accordingly. If
  an author wants to skip a level, e.g. from level 1 to level 3,
  they can do that. In general, the heading levels specified
  in the source document are preserved; `makeSections` only
  puts them into a hierarchical structure. Closes #9398.

+ Section numbers are now assigned so that the top level
  gets `1`, no matter what heading level is used. So, even
  if the top heading level is 2, numbers will be `1`, `2`, etc.
  rather than `0.1`, `0.2`, as in the past. Closes #5071.

+ We revert to the old behavior when the `--number-offset` option
  is used. So, for example, if a document begins with a level-3
  heading, and `--number-offset=1,2` is used, the top-level section
  numbers will be `1.2.1`, `1.2.2`, etc. This is mainly for
  backwards-compatibility.

1 files changed, 11 insertions, 6 deletions

diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 18e10f102..c7a4703ae 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -721,17 +721,22 @@ adjustNumbers opts doc =
      then doc
      else walk go doc
   where
-   go (Div (ident,"section":classes,kvs) lst) =
-     Div (ident,"section":classes,map fixnum kvs) lst
+   go (Div (ident,"section":classes,kvs) lst@(Header level _ _ : _)) =
+     Div (ident,"section":classes,map (fixnum level) kvs) lst
    go (Header level (ident,classes,kvs) lst) =
-     Header level (ident,classes,map fixnum kvs) lst
+     Header level (ident,classes,map (fixnum level) kvs) lst
    go x = x
-   fixnum ("number",num) = ("number",
+   fixnum level ("number",num) = ("number",
                                showSecNum $ zipWith (+)
                                (writerNumberOffset opts ++ repeat 0)
-                               (map (fromMaybe 0 . safeRead) $
+                               (padTo level $
+                                map (fromMaybe 0 . safeRead) $
                                 T.split (=='.') num))
-   fixnum x = x
+   fixnum _ x = x
+   padTo n xs =
+     case n - length xs of
+       x | x > 0 -> replicate x 0 ++ xs
+         | otherwise -> xs
    showSecNum = T.intercalate "." . map tshow
 
 blockToHtmlInner :: PandocMonad m => WriterOptions -> Block -> StateT WriterState m Html