Wrap emojis in span nodes (#4759)

Text.Pandoc.Emoji now exports `emojiToInline`, which returns a Span inline containing the emoji character and some attributes with metadata (class `emoji`, attribute `data-emoji` with emoji name).  Previously, emojis (as supported in Markdown and CommonMark readers, e.g ":smile:")
were simply translated into the corresponding unicode code point.  By wrapping them in Span
nodes, we make it possible to do special handling such as giving them a special font
in HTML output.  We also open up the possibility of treating them differently when the
`--ascii` option is selected (though that is not part of this commit).

Closes #4743.

3 files changed, 27 insertions, 19 deletions

diff --git a/src/Text/Pandoc/Emoji.hs b/src/Text/Pandoc/Emoji.hs
index 5cc965153..7d0af1a72 100644
--- a/src/Text/Pandoc/Emoji.hs
+++ b/src/Text/Pandoc/Emoji.hs
@@ -28,9 +28,10 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 Emoji symbol lookup from canonical string identifier.
 -}
-module Text.Pandoc.Emoji ( emojis ) where
+module Text.Pandoc.Emoji ( emojis, emojiToInline ) where
 import Prelude
 import qualified Data.Map as M
+import Text.Pandoc.Definition (Inline (Span, Str))
 
 emojis :: M.Map String String
 emojis = M.fromList
@@ -905,3 +906,7 @@ emojis = M.fromList
   ,("zero","0\65039\8419")
   ,("zzz","\128164")
   ]
+
+emojiToInline :: String -> Maybe Inline
+emojiToInline emojikey = makeSpan <$> M.lookup emojikey emojis
+  where makeSpan = Span ("", ["emoji"], [("data-emoji", emojikey)]) . (:[]) . Str
diff --git a/src/Text/Pandoc/Readers/CommonMark.hs b/src/Text/Pandoc/Readers/CommonMark.hs
index a742ca666..9c4f7a8ac 100644
--- a/src/Text/Pandoc/Readers/CommonMark.hs
+++ b/src/Text/Pandoc/Readers/CommonMark.hs
@@ -44,7 +44,7 @@ import Data.Text (Text, unpack)
 import Text.Pandoc.Asciify (toAsciiChar)
 import Text.Pandoc.Class (PandocMonad)
 import Text.Pandoc.Definition
-import Text.Pandoc.Emoji (emojis)
+import Text.Pandoc.Emoji (emojiToInline)
 import Text.Pandoc.Options
 import Text.Pandoc.Shared (stringify)
 import Text.Pandoc.Walk (walkM)
@@ -61,16 +61,19 @@ readCommonMark opts s = return $
                [ extTable | isEnabled Ext_pipe_tables opts ] ++
                [ extAutolink | isEnabled Ext_autolink_bare_uris opts ]
 
-convertEmojis :: String -> String
-convertEmojis (':':xs) =
+convertEmojis :: String -> [Inline]
+convertEmojis s@(':':xs) =
    case break (==':') xs of
         (ys,':':zs) ->
-           case Map.lookup ys emojis of
-                Just s  -> s ++ convertEmojis zs
-                Nothing -> ':' : ys ++ convertEmojis (':':zs)
-        _ -> ':':xs
-convertEmojis (x:xs) = x : convertEmojis xs
-convertEmojis [] = []
+           case emojiToInline ys of
+                Just em -> em : convertEmojis zs
+                Nothing -> Str (':' : ys) : convertEmojis (':':zs)
+        _ -> [Str s]
+convertEmojis s =
+  case break (==':') s of
+    ("","") -> []
+    (_,"") -> [Str s]
+    (xs,ys) -> Str xs:convertEmojis ys
 
 addHeaderIdentifiers :: ReaderOptions -> Pandoc -> Pandoc
 addHeaderIdentifiers opts doc = evalState (walkM (addHeaderId opts) doc) mempty
@@ -205,17 +208,17 @@ addInlines :: ReaderOptions -> [Node] -> [Inline]
 addInlines opts = foldr (addInline opts) []
 
 addInline :: ReaderOptions -> Node -> [Inline] -> [Inline]
-addInline opts (Node _ (TEXT t) _) = (map toinl clumps ++)
+addInline opts (Node _ (TEXT t) _) = (foldr ((++) . toinl) [] clumps ++)
   where raw = unpack t
         clumps = groupBy samekind raw
         samekind ' ' ' ' = True
         samekind ' ' _   = False
         samekind _   ' ' = False
         samekind _  _    = True
-        toinl (' ':_) = Space
-        toinl xs      = Str $ if isEnabled Ext_emoji opts
-                                 then convertEmojis xs
-                                 else xs
+        toinl (' ':_) = [Space]
+        toinl xs      = if isEnabled Ext_emoji opts
+                        then convertEmojis xs
+                        else [Str xs]
 addInline _ (Node _ LINEBREAK _) = (LineBreak :)
 addInline opts (Node _ SOFTBREAK _)
   | isEnabled Ext_hard_line_breaks opts = (LineBreak :)
diff --git a/src/Text/Pandoc/Readers/Markdown.hs b/src/Text/Pandoc/Readers/Markdown.hs
index 68f076e35..e491f6276 100644
--- a/src/Text/Pandoc/Readers/Markdown.hs
+++ b/src/Text/Pandoc/Readers/Markdown.hs
@@ -51,7 +51,7 @@ import Text.Pandoc.Builder (Blocks, Inlines)
 import qualified Text.Pandoc.Builder as B
 import Text.Pandoc.Class (PandocMonad (..), report)
 import Text.Pandoc.Definition
-import Text.Pandoc.Emoji (emojis)
+import Text.Pandoc.Emoji (emojiToInline)
 import Text.Pandoc.Error
 import Text.Pandoc.Logging
 import Text.Pandoc.Options
@@ -2027,9 +2027,9 @@ emoji = try $ do
   char ':'
   emojikey <- many1 (oneOf emojiChars)
   char ':'
-  case M.lookup emojikey emojis of
-       Just s  -> return (return (B.str s))
-       Nothing -> mzero
+  case emojiToInline emojikey of
+    Just i -> return (return $ B.singleton i)
+    Nothing -> mzero
 
 -- Citations