Lua: allow to get the JSON encoding of log messages

1 files changed, 5 insertions, 0 deletions

diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/CommonState.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/CommonState.hs
index 28cb5925b..376f2dd74 100644
--- a/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/CommonState.hs
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/CommonState.hs
@@ -19,6 +19,7 @@ import HsLua
 import Text.Pandoc.Class (CommonState (..))
 import Text.Pandoc.Logging (LogMessage, showLogMessage)
 import Text.Pandoc.Lua.Marshal.List (pushPandocList)
+import qualified Data.Aeson as Aeson
 
 -- | Lua type used for the @CommonState@ object.
 typeCommonState :: LuaError e => DocumentedType e CommonState
@@ -64,5 +65,9 @@ typeLogMessage = deftype "pandoc LogMessage"
       ### liftPure showLogMessage
       <#> udparam typeLogMessage "msg" "object"
       =#> functionResult pushText "string" "stringified log message"
+  , operation (CustomOperation "__tojson") $ lambda
+      ### liftPure Aeson.encode
+      <#> udparam typeLogMessage "msg" "object"
+      =#> functionResult pushLazyByteString "string" "JSON encoded object"
   ]
   mempty -- no members