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/Docbook.hs b/src/Text/Pandoc/Writers/Docbook.hs
index 5c03d449d..74e3bff3d 100644
--- a/src/Text/Pandoc/Writers/Docbook.hs
+++ b/src/Text/Pandoc/Writers/Docbook.hs
@@ -47,6 +47,7 @@ import qualified Text.Pandoc.Builder as B
 import Text.TeXMath
 import qualified Text.XML.Light as Xml
 import Data.Generics (everywhere, mkT)
+import Text.Pandoc.Class (PandocMonad)
 
 -- | Convert list of authors to a docbook <author> section
 authorToDocbook :: WriterOptions -> [Inline] -> B.Inlines
@@ -73,8 +74,8 @@ authorToDocbook opts name' =
                   inTagsSimple "surname" (text $ escapeStringForXML lastname)
 
 -- | Convert Pandoc document to string in Docbook format.
-writeDocbook :: WriterOptions -> Pandoc -> String
-writeDocbook opts (Pandoc meta blocks) =
+writeDocbook :: PandocMonad m => WriterOptions -> Pandoc -> m String
+writeDocbook opts (Pandoc meta blocks) = return $
   let elements = hierarchicalize blocks
       colwidth = if writerWrapText opts == WrapAuto
                     then Just $ writerColumns opts