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/RST.hs b/src/Text/Pandoc/Writers/RST.hs
index c170889cc..438407cce 100644
--- a/src/Text/Pandoc/Writers/RST.hs
+++ b/src/Text/Pandoc/Writers/RST.hs
@@ -44,6 +44,7 @@ import Network.URI (isURI)
 import Text.Pandoc.Pretty
 import Control.Monad.State
 import Data.Char (isSpace, toLower)
+import Text.Pandoc.Class (PandocMonad)
 
 type Refs = [([Inline], Target)]
 
@@ -58,8 +59,8 @@ data WriterState =
               }
 
 -- | Convert Pandoc to RST.
-writeRST :: WriterOptions -> Pandoc -> String
-writeRST opts document =
+writeRST :: PandocMonad m => WriterOptions -> Pandoc -> m String
+writeRST opts document = return $
   let st = WriterState { stNotes = [], stLinks = [],
                          stImages = [], stHasMath = False,
                          stHasRawTeX = False, stOptions = opts,