RST redear: Fix sorting on anonymous keys.

This fixes a bug in RST documents that have anonymous links.
Closes #8877.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Readers/RST.hs b/src/Text/Pandoc/Readers/RST.hs
index dcaddaa60..08ea50155 100644
--- a/src/Text/Pandoc/Readers/RST.hs
+++ b/src/Text/Pandoc/Readers/RST.hs
@@ -25,6 +25,7 @@ import Data.Maybe (fromMaybe, maybeToList, isJust)
 import Data.Sequence (ViewR (..), viewr)
 import Data.Text (Text)
 import qualified Data.Text as T
+import Text.Printf (printf)
 import Text.Pandoc.Builder (Blocks, Inlines, fromList, setMeta, trimInlines)
 import qualified Text.Pandoc.Builder as B
 import Text.Pandoc.Class.PandocMonad (PandocMonad, fetchItem, getTimestamp)
@@ -1164,14 +1165,14 @@ substKey = try $ do
   updateState $ \s -> s{ stateSubstitutions =
                           M.insert key il $ stateSubstitutions s }
 
-anonymousKey :: Monad m => RSTParser m ()
+anonymousKey :: PandocMonad m => RSTParser m ()
 anonymousKey = try $ do
   oneOfStrings [".. __:", "__"]
   src <- targetURI
   -- we need to ensure that the keys are ordered by occurrence in
   -- the document.
   numKeys <- M.size . stateKeys <$> getState
-  let key = toKey $ "_" <> T.pack (show numKeys)
+  let key = toKey $ "_" <> T.pack (printf "%04d" numKeys)
   updateState $ \s -> s { stateKeys = M.insert key ((src,""), nullAttr) $
                           stateKeys s }