Convert all writers to use PandocMonad.

Since PandocMonad is an instance of MonadError, this will allow us, in a
future commit, to change all invocations of `error` to `throwError`,
which will be preferable for the pure versions. At the moment, we're
disabling the lua custom writers (this is temporary).

This requires changing the type of the Writer in Text.Pandoc. Right now,
we run `runIOorExplode` in pandoc.hs, to make the conversion easier. We
can switch it to the safer `runIO` in the future.

Note that this required a change to Text.Pandoc.PDF as well. Since
running an external program is necessarily IO, we can be clearer about
using PandocIO.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Writers/Man.hs b/src/Text/Pandoc/Writers/Man.hs
index 304995ec8..75c026463 100644
--- a/src/Text/Pandoc/Writers/Man.hs
+++ b/src/Text/Pandoc/Writers/Man.hs
@@ -41,14 +41,15 @@ import Data.Maybe (fromMaybe)
 import Text.Pandoc.Pretty
 import Text.Pandoc.Builder (deleteMeta)
 import Control.Monad.State
+import Text.Pandoc.Class (PandocMonad)
 
 type Notes = [[Block]]
 data WriterState = WriterState { stNotes  :: Notes
                                , stHasTables :: Bool }
 
 -- | Convert Pandoc to Man.
-writeMan :: WriterOptions -> Pandoc -> String
-writeMan opts document = evalState (pandocToMan opts document) (WriterState [] False)
+writeMan :: PandocMonad m => WriterOptions -> Pandoc -> m String
+writeMan opts document = return $ evalState (pandocToMan opts document) (WriterState [] False)
 
 -- | Return groff man representation of document.
 pandocToMan :: WriterOptions -> Pandoc -> State WriterState String