RST reader: handle class attribute for for custom roles (#7700)

Previously the class attribute was ignored, and the name of the role used as the class.
Closes #7699.

src/Text/Pandoc/Readers/RST.hs

@@ -919,14 +919,22 @@ addNewRole roleText fields = do
         (baseRole, baseFmt, baseAttr) =
                getBaseRole (parentRole, Nothing, nullAttr) customRoles
         fmt = if parentRole == "raw" then lookup "format" fields else baseFmt
-        annotate :: [Text] -> [Text]
-        annotate = maybe id (:) $
-            if baseRole == "code"
-               then lookup "language" fields
-               else Nothing
-        attr = let (ident, classes, keyValues) = baseAttr
-        -- nub in case role name & language class are the same
-               in (ident, nub . (role :) . annotate $ classes, keyValues)
+
+        updateClasses :: [Text] -> [Text]
+        updateClasses oldClasses = let
+
+          codeLanguageClass = if baseRole == "code"
+            then maybeToList (lookup "language" fields)
+            else []
+
+          -- if no ":class:" field is given, the default is the role name
+          classFieldClasses = maybe [role] T.words (lookup "class" fields)
+
+          -- nub in case role name & language class are the same
+          in nub (classFieldClasses ++ codeLanguageClass ++ oldClasses)
+
+        attr = let (ident, baseClasses, keyValues) = baseAttr
+               in (ident, updateClasses baseClasses, keyValues)
 
     -- warn about syntax we ignore
     forM_ fields $ \(key, _) -> case key of

test/Tests/Readers/RST.hs

@@ -179,6 +179,15 @@ tests = [ "line block with blank line" =:
           , "custom code role with language field"
             =: ".. role:: lhs(code)\n    :language: haskell\n\n:lhs:`a`"
             =?> para (codeWith ("", ["lhs", "haskell"], []) "a")
+          , "custom role with class field"
+            =: ".. role:: classy\n    :class: myclass\n\n:classy:`a`"
+            =?> para (spanWith ("", ["myclass"], []) "a")
+          , "custom role with class field containing multiple whitespace-separated classes"
+            =: ".. role:: classy\n    :class: myclass1 myclass2\n       myclass3\n\n:classy:`a`"
+            =?> para (spanWith ("", ["myclass1", "myclass2", "myclass3"], []) "a")
+          , "custom role with inherited class field"
+            =: ".. role:: classy\n    :class: myclass1\n.. role:: classier(classy)\n    :class: myclass2\n\n:classier:`a`"
+            =?> para (spanWith ("", ["myclass2", "myclass1"], []) "a")
           , "custom role with unspecified parent role"
             =: ".. role:: classy\n\n:classy:`text`"
             =?> para (spanWith ("", ["classy"], []) "text")