From 5d9fc469920ae7962c1fdde7efcb78b889010d24 Mon Sep 17 00:00:00 2001
From: John MacFarlane <fiddlosopher@gmail.com>
Date: Fri, 4 Jan 2013 12:08:18 -0800
Subject: Markdown reader: Warn about duplicate note references.

Closes #375.
---
 src/Text/Pandoc/Readers/Markdown.hs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'src/Text/Pandoc/Readers')

diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index 16141369a..985d1d0f2 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -317,6 +317,7 @@ rawLines = do
 
 noteBlock :: MarkdownParser (F Blocks)
 noteBlock = try $ do
+  pos <- getPosition
   skipNonindentSpaces
   ref <- noteMarker
   char ':'
@@ -328,7 +329,11 @@ noteBlock = try $ do
   optional blanklines
   parsed <- parseFromString parseBlocks raw
   let newnote = (ref, parsed)
-  updateState $ \s -> s { stateNotes' = newnote : stateNotes' s }
+  oldnotes <- stateNotes' <$> getState
+  case lookup ref oldnotes of
+    Just _  -> addWarning (Just pos) $ "Duplicate note reference `" ++ ref ++ "'"
+    Nothing -> return ()
+  updateState $ \s -> s { stateNotes' = newnote : oldnotes }
   return mempty
 
 --
-- 
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