Escape MetaString values (as added with --metadata flag).

Previously they would be transmitted to the template without
any escaping.

Note that `--M title='*foo*'` yields a different result from

    ---
    title: *foo*
    ---

In the latter case, we have emphasis; in the former case, just
a string with literal asterisks (which will be escaped
in formats, like Markdown, that require it).

Closes #3792.

1 files changed, 8 insertions, 6 deletions

diff --git a/src/Text/Pandoc/Writers/Shared.hs b/src/Text/Pandoc/Writers/Shared.hs
index 8369bc09c..c6a5fdaf8 100644
--- a/src/Text/Pandoc/Writers/Shared.hs
+++ b/src/Text/Pandoc/Writers/Shared.hs
@@ -42,7 +42,7 @@ module Text.Pandoc.Writers.Shared (
                      , gridTable
                      )
 where
-import Control.Monad (liftM, zipWithM)
+import Control.Monad (zipWithM)
 import Data.Aeson (FromJSON (..), Result (..), ToJSON (..), Value (Object),
                    encode, fromJSON)
 import qualified Data.HashMap.Strict as H
@@ -51,6 +51,7 @@ import qualified Data.Map as M
 import Data.Maybe (isJust)
 import qualified Data.Text as T
 import qualified Data.Traversable as Traversable
+import qualified Text.Pandoc.Builder as Builder
 import Text.Pandoc.Definition
 import Text.Pandoc.Options
 import Text.Pandoc.Pretty
@@ -103,14 +104,15 @@ metaValueToJSON :: (Monad m, ToJSON a)
                 -> ([Inline] -> m a)
                 -> MetaValue
                 -> m Value
-metaValueToJSON blockWriter inlineWriter (MetaMap metamap) = liftM toJSON $
+metaValueToJSON blockWriter inlineWriter (MetaMap metamap) = toJSON <$>
   Traversable.mapM (metaValueToJSON blockWriter inlineWriter) metamap
-metaValueToJSON blockWriter inlineWriter (MetaList xs) = liftM toJSON $
+metaValueToJSON blockWriter inlineWriter (MetaList xs) = toJSON <$>
   Traversable.mapM (metaValueToJSON blockWriter inlineWriter) xs
 metaValueToJSON _ _ (MetaBool b) = return $ toJSON b
-metaValueToJSON _ _ (MetaString s) = return $ toJSON s
-metaValueToJSON blockWriter _ (MetaBlocks bs) = liftM toJSON $ blockWriter bs
-metaValueToJSON _ inlineWriter (MetaInlines bs) = liftM toJSON $ inlineWriter bs
+metaValueToJSON _ inlineWriter (MetaString s) = toJSON <$>
+  inlineWriter (Builder.toList (Builder.text s))
+metaValueToJSON blockWriter _ (MetaBlocks bs) = toJSON <$> blockWriter bs
+metaValueToJSON _ inlineWriter (MetaInlines is) = toJSON <$> inlineWriter is
 
 -- | Retrieve a field value from a JSON object.
 getField :: FromJSON a