RST reader/writer: support unknown interpreted text roles...

...by parsing them as Span with "role" attributes.
This way they can be manipulated in the AST.

Closes #3407.

src/Text/Pandoc/Readers/RST.hs

@@ -1399,10 +1399,8 @@ renderRole contents fmt role attr = case role of
         case M.lookup custom customRoles of
             Just (newRole, newFmt, newAttr) ->
                 renderRole contents newFmt newRole newAttr
-            Nothing -> do
-                pos <- getPosition
-                logMessage $ SkippedContent (":" ++ custom ++ ":") pos
-                return $ B.str contents -- Undefined role
+            Nothing -> -- undefined role
+                return $ B.spanWith ("",[],[("role",role)]) (B.str contents)
  where
    titleRef ref = return $ B.str ref -- FIXME: Not a sensible behaviour
    rfcLink rfcNo = B.link rfcUrl ("RFC " ++ rfcNo) $ B.str ("RFC " ++ rfcNo)

src/Text/Pandoc/Writers/RST.hs

@@ -439,7 +439,12 @@ inlineListToRST lst =
 
 -- | Convert Pandoc inline element to RST.
 inlineToRST :: PandocMonad m => Inline -> RST m Doc
-inlineToRST (Span _ ils) = inlineListToRST ils
+inlineToRST (Span (_,_,kvs) ils) = do
+  contents <- inlineListToRST ils
+  return $
+    case lookup "role" kvs of
+          Just role -> ":" <> text role <> ":`" <> contents <> "`"
+          Nothing   -> contents
 inlineToRST (Emph lst) = do
   contents <- inlineListToRST lst
   return $ "*" <> contents <> "*"

test/Tests/Readers/RST.hs

@@ -162,7 +162,8 @@ tests = [ "line block with blank line" =:
           , "role with recursive inheritance"
             =: ".. role:: haskell(code)\n.. role:: lhs(haskell)\n\n:lhs:`text`"
             =?> para (codeWith ("", ["lhs", "haskell", "sourceCode"], []) "text")
-          , "unknown role" =: ":unknown:`text`" =?> para (str "text")
+          , "unknown role" =: ":unknown:`text`" =?>
+              para (spanWith ("",[],[("role","unknown")]) (str "text"))
           ]
         , testGroup "footnotes"
           [ "remove space before note" =: T.unlines

test/command/3407.md

@@ -0,0 +1,13 @@
+```
+% pandoc -f native -t rst
+[Para [Span ("",[],[("role","foo")]) [Str "text"]]]
+^D
+:foo:`text`
+```
+
+```
+% pandoc -f rst -t native
+:foo:`text`
+^D
+[Para [Span ("",[],[("role","foo")]) [Str "text"]]]
+```