Syntax highlight for inline code of OpenDocument (#6711)

To implement Syntax highlighting for OpenDocument, inlineToOpenDocument in OpenDocument Writer is updated based on Docx Writer.
This commit is only for inline Code because update of CodeBlock needs structual change of output document.
Currently, styles are not generated automatically in styles.xml. To implement it, additional commit for ODT Writer is needed.
Although styles are not included in styles.xml, output file can be shown in LibreOffice(7.0.0.3) like normal characters.

src/Text/Pandoc/Writers/OpenDocument.hs

@@ -19,7 +19,7 @@ import Control.Monad.State.Strict hiding (when)
 import Data.Char (chr)
 import Data.List (sortOn, sortBy, foldl')
 import qualified Data.Map as Map
-import Data.Maybe (fromMaybe)
+import Data.Maybe (fromMaybe, isNothing)
 import Data.Ord (comparing)
 import qualified Data.Set as Set
 import Data.Text (Text)
@@ -40,6 +40,8 @@ import Text.Pandoc.Writers.Shared
 import qualified Text.Pandoc.Writers.AnnotatedTable as Ann
 import Text.Pandoc.XML
 import Text.Printf (printf)
+import Text.Pandoc.Highlighting (highlight)
+import Skylighting
 
 -- | Auxiliary function to convert Plain block to Para.
 plainToPara :: Block -> Block
@@ -563,7 +565,7 @@ inlineToOpenDocument o ils
     SoftBreak
      | writerWrapText o == WrapPreserve
                   -> return $ preformatted "\n"
-     | otherwise  ->return space
+     | otherwise  -> return space
     Span attr xs  -> withLangFromAttr attr (inlinesToOpenDocument o xs)
     LineBreak     -> return $ selfClosingTag "text:line-break" []
     Str         s -> return $ handleSpaces $ escapeStringForXML s
@@ -575,7 +577,14 @@ inlineToOpenDocument o ils
     Subscript   l -> withTextStyle Sub    $ inlinesToOpenDocument o l
     SmallCaps   l -> withTextStyle SmallC $ inlinesToOpenDocument o l
     Quoted    t l -> inQuotes t <$> inlinesToOpenDocument o l
-    Code      _ s -> inlinedCode $ preformatted s
+    Code      attrs s -> if isNothing (writerHighlightStyle o)
+      then unhighlighted s
+      else case highlight (writerSyntaxMap o)
+                  formatOpenDocument attrs s of
+                Right h  -> return $ mconcat $ mconcat h
+                Left msg -> do
+                  unless (T.null msg) $ report $ CouldNotHighlight msg
+                  unhighlighted s
     Math      t s -> lift (texMathToInlines t s) >>=
                          inlinesToOpenDocument o
     Cite      _ l -> inlinesToOpenDocument o l
@@ -588,6 +597,12 @@ inlineToOpenDocument o ils
     Image attr _ (s,t) -> mkImg attr s t
     Note        l  -> mkNote l
     where
+      formatOpenDocument :: FormatOptions -> [SourceLine] -> [[Doc Text]]
+      formatOpenDocument _fmtOpts = map (map toHlTok)
+      toHlTok :: Token -> Doc Text
+      toHlTok (toktype,tok) =
+        inTags False "text:span" [("text:style-name", (T.pack $ show toktype))] $ preformatted tok
+      unhighlighted s = inlinedCode $ preformatted s
       preformatted s = handleSpaces $ escapeStringForXML s
       inlinedCode s = return $ inTags False "text:span" [("text:style-name", "Source_Text")] s
       mkLink   s t = inTags False "text:a" [ ("xlink:type" , "simple")