Add custom extensions.

T.P.Extensions [API change]:

+ Add CustomExtension constructor to Extension.
+ Remove Bounded, Enum instances for Extension.
+ Add `extensionsToList` function.
+ Revise `readExtension` so it can handle CustomExtension, and so
  that it returns a Text rather than Maybe Text.
+ Add `showExtension`.

T.P.Format:

+ Revise error checking to handle CustomExtension.

1 files changed, 1 insertions, 5 deletions

diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/Format.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/Format.hs
index a71aeb952..377ce159b 100644
--- a/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/Format.hs
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/Marshal/Format.hs
@@ -19,16 +19,12 @@ module Text.Pandoc.Lua.Marshal.Format
 import HsLua
 import Text.Pandoc.Extensions (Extension, Extensions, extensionsFromList, readExtension)
 import Text.Pandoc.Format (ExtensionsConfig (..))
-import qualified HsLua.Core.Utf8 as UTF8
 
 -- | Retrieves an 'Extensions' set from the Lua stack.
 peekExtension :: LuaError e => Peeker e Extension
 peekExtension idx = do
   extString <- peekString idx
-  case readExtension extString of
-    Just ext -> return ext
-    Nothing  -> failPeek . UTF8.fromString $
-                "Unknown extension: " <> extString
+  return $ readExtension extString
 {-# INLINE peekExtension #-}
 
 -- | Retrieves an 'Extensions' set from the Lua stack.