Change return type of Native reader

src/Text/Pandoc/Readers/Native.hs

@@ -3,7 +3,7 @@ Copyright (C) 2011-2014 John MacFarlane <jgm@berkeley.edu>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
-the Free Software Foundation; either version 2 of the License, or
+the Free Software Foundation; Either version 2 of the License, or
 (at your option) any later version.
 
 This program is distributed in the hope that it will be useful,
@@ -33,6 +33,9 @@ module Text.Pandoc.Readers.Native ( readNative ) where
 import Text.Pandoc.Definition
 import Text.Pandoc.Shared (safeRead)
 
+import Text.Pandoc.Error
+import Control.Applicative
+
 -- | Read native formatted text and return a Pandoc document.
 -- The input may be a full pandoc document, a block list, a block,
 -- an inline list, or an inline.  Thus, for example,
@@ -44,33 +47,18 @@ import Text.Pandoc.Shared (safeRead)
 -- > Pandoc nullMeta [Plain [Str "hi"]]
 --
 readNative :: String      -- ^ String to parse (assuming @'\n'@ line endings)
-           -> Pandoc
-readNative s =
-  case safeRead s of
-       Just d    -> d
-       Nothing   -> Pandoc nullMeta $ readBlocks s
+           -> Either PandocError Pandoc
+readNative s = maybe (Pandoc nullMeta <$> readBlocks s) Right (safeRead s)
 
-readBlocks :: String -> [Block]
-readBlocks s =
-  case safeRead s of
-       Just d    -> d
-       Nothing   -> [readBlock s]
+readBlocks :: String -> Either PandocError [Block]
+readBlocks s = maybe ((:[]) <$> readBlock s) Right (safeRead s)
 
-readBlock :: String -> Block
-readBlock s =
-  case safeRead s of
-       Just d    -> d
-       Nothing   -> Plain $ readInlines s
+readBlock :: String -> Either PandocError Block
+readBlock s = maybe (Plain <$> readInlines s) Right (safeRead s)
 
-readInlines :: String -> [Inline]
-readInlines s =
-  case safeRead s of
-       Just d     -> d
-       Nothing    -> [readInline s]
+readInlines :: String -> Either PandocError [Inline]
+readInlines s = maybe ((:[]) <$> readInline s) Right (safeRead s)
 
-readInline :: String -> Inline
-readInline s =
-  case safeRead s of
-       Just d     -> d
-       Nothing    -> error "Cannot parse document"
+readInline :: String -> Either PandocError Inline
+readInline s = maybe (Left . ParseFailure $ "Could not read: " ++ s) Right (safeRead s)