Markdown reader: warn for notes defined but not used.

Closes #1718.

Parsing.ParserState: Make stateNotes' a Map, add stateNoteRefs.

src/Text/Pandoc/Logging.hs

@@ -72,6 +72,7 @@ data LogMessage =
   | CouldNotParseYamlMetadata String SourcePos
   | DuplicateLinkReference String SourcePos
   | DuplicateNoteReference String SourcePos
+  | NoteDefinedButNotUsed String SourcePos
   | DuplicateIdentifier String SourcePos
   | ReferenceNotFound String SourcePos
   | CircularReference String SourcePos
@@ -113,6 +114,11 @@ instance ToJSON LogMessage where
             "source" .= Text.pack (sourceName pos),
             "line" .= toJSON (sourceLine pos),
             "column" .= toJSON (sourceColumn pos)]
+      NoteDefinedButNotUsed s pos ->
+           ["key" .= Text.pack s,
+            "source" .= Text.pack (sourceName pos),
+            "line" .= toJSON (sourceLine pos),
+            "column" .= toJSON (sourceColumn pos)]
       DuplicateNoteReference s pos ->
            ["contents" .= Text.pack s,
             "source" .= Text.pack (sourceName pos),
@@ -203,6 +209,9 @@ showLogMessage msg =
          "Duplicate link reference '" ++ s ++ "' at " ++ showPos pos
        DuplicateNoteReference s pos ->
          "Duplicate note reference '" ++ s ++ "' at " ++ showPos pos
+       NoteDefinedButNotUsed s pos ->
+         "Note with key '" ++ s ++ "' defined at " ++ showPos pos ++
+           " but not used."
        DuplicateIdentifier s pos ->
          "Duplicate identifier '" ++ s ++ "' at " ++ showPos pos
        ReferenceNotFound s pos ->
@@ -256,6 +265,7 @@ messageVerbosity msg =
        CouldNotParseYamlMetadata{}  -> WARNING
        DuplicateLinkReference{}     -> WARNING
        DuplicateNoteReference{}     -> WARNING
+       NoteDefinedButNotUsed{}      -> WARNING
        DuplicateIdentifier{}        -> WARNING
        ReferenceNotFound{}          -> WARNING
        CircularReference{}          -> WARNING

src/Text/Pandoc/Parsing.hs

@@ -983,6 +983,7 @@ data ParserState = ParserState
       stateSubstitutions   :: SubstTable,    -- ^ List of substitution references
       stateNotes           :: NoteTable,     -- ^ List of notes (raw bodies)
       stateNotes'          :: NoteTable',    -- ^ List of notes (parsed bodies)
+      stateNoteRefs        :: Set.Set String, -- ^ List of note references used
       stateMeta            :: Meta,          -- ^ Document metadata
       stateMeta'           :: F Meta,        -- ^ Document metadata
       stateCitations       :: M.Map String String, -- ^ RST-style citations
@@ -1099,7 +1100,8 @@ defaultParserState =
                   stateHeaderKeys      = M.empty,
                   stateSubstitutions   = M.empty,
                   stateNotes           = [],
-                  stateNotes'          = [],
+                  stateNotes'          = M.empty,
+                  stateNoteRefs        = Set.empty,
                   stateMeta            = nullMeta,
                   stateMeta'           = return nullMeta,
                   stateCitations       = M.empty,
@@ -1166,7 +1168,8 @@ data QuoteContext
 
 type NoteTable = [(String, String)]
 
-type NoteTable' = [(String, F Blocks)]  -- used in markdown reader
+type NoteTable' = M.Map String (SourcePos, F Blocks)
+-- used in markdown reader
 
 newtype Key = Key String deriving (Show, Read, Eq, Ord)
 

src/Text/Pandoc/Readers/Markdown.hs

@@ -362,6 +362,14 @@ parseMarkdown = do
   optional titleBlock
   blocks <- parseBlocks
   st <- getState
+  -- check for notes with no corresponding note references
+  let notesUsed = stateNoteRefs st
+  let notesDefined = M.keys (stateNotes' st)
+  mapM_ (\n -> unless (n `Set.member` notesUsed) $ do
+                -- lookup to get sourcepos
+                case M.lookup n (stateNotes' st) of
+                   Just (pos, _) -> report (NoteDefinedButNotUsed n pos)
+                   Nothing -> error "The impossible happened.") notesDefined
   let doc = runF (do Pandoc _ bs <- B.doc <$> blocks
                      meta <- stateMeta' st
                      return $ Pandoc meta bs) st
@@ -469,12 +477,11 @@ noteBlock = try $ do
   let raw = unlines (first:rest) ++ "\n"
   optional blanklines
   parsed <- parseFromString' parseBlocks raw
-  let newnote = (ref, parsed)
   oldnotes <- stateNotes' <$> getState
-  case lookup ref oldnotes of
+  case M.lookup ref oldnotes of
     Just _  -> logMessage $ DuplicateNoteReference ref pos
     Nothing -> return ()
-  updateState $ \s -> s { stateNotes' = newnote : oldnotes }
+  updateState $ \s -> s { stateNotes' = M.insert ref (pos, parsed) oldnotes }
   return mempty
 
 --
@@ -1816,16 +1823,17 @@ note :: PandocMonad m => MarkdownParser m (F Inlines)
 note = try $ do
   guardEnabled Ext_footnotes
   ref <- noteMarker
+  updateState $ \st -> st{ stateNoteRefs = Set.insert ref (stateNoteRefs st) }
   return $ do
     notes <- asksF stateNotes'
-    case lookup ref notes of
+    case M.lookup ref notes of
         Nothing       -> return $ B.str $ "[^" ++ ref ++ "]"
-        Just contents -> do
+        Just (_pos, contents) -> do
           st <- askF
           -- process the note in a context that doesn't resolve
           -- notes, to avoid infinite looping with notes inside
           -- notes:
-          let contents' = runF contents st{ stateNotes' = [] }
+          let contents' = runF contents st{ stateNotes' = M.empty }
           return $ B.note contents'
 
 inlineNote :: PandocMonad m => MarkdownParser m (F Inlines)