Text.Pandoc.App: Throw errors rather than exiting.

These are caught (and lead to exit) in pandoc.hs, but
other uses of Text.Pandoc.App may want to recover in another
way.

Added PandocAppError to PandocError (API change).
This is a stopgap:  later we should have a separate constructor
for each type of error.

Also fixed uses of 'exit' in Shared.readDataFile, and
removed 'err' from Shared (API change).

Finally, removed the dependency on extensible-exceptions.

See #3548.

1 files changed, 4 insertions, 12 deletions

diff --git a/src/Text/Pandoc/Shared.hs b/src/Text/Pandoc/Shared.hs
index 3b9ae7501..dfdbaf428 100644
--- a/src/Text/Pandoc/Shared.hs
+++ b/src/Text/Pandoc/Shared.hs
@@ -82,7 +82,6 @@ module Text.Pandoc.Shared (
                      collapseFilePath,
                      filteredFilesFromArchive,
                      -- * Error handling
-                     err,
                      mapLeft,
                      -- * for squashing blocks
                      blocksToInlines,
@@ -99,7 +98,6 @@ import Text.Pandoc.Walk
 import Text.Pandoc.Builder (Inlines, Blocks, ToMetaValue(..))
 import qualified Text.Pandoc.Builder as B
 import qualified Text.Pandoc.UTF8 as UTF8
-import System.Exit (exitWith, ExitCode(..))
 import Data.Char ( toLower, isLower, isUpper, isAlpha,
                    isLetter, isDigit, isSpace )
 import Data.List ( find, stripPrefix, intercalate )
@@ -112,16 +110,15 @@ import System.Directory
 import System.FilePath (splitDirectories, isPathSeparator)
 import qualified System.FilePath.Posix as Posix
 import Text.Pandoc.MIME (MimeType)
+import Text.Pandoc.Error (PandocError(..))
 import System.FilePath ( (</>) )
 import Data.Generics (Typeable, Data)
 import qualified Control.Monad.State as S
-import Control.Monad.Trans (MonadIO (..))
 import qualified Control.Exception as E
 import Control.Monad (msum, unless, MonadPlus(..))
 import Text.Pandoc.Pretty (charWidth)
 import Text.Pandoc.Compat.Time
 import Data.Time.Clock.POSIX
-import System.IO (stderr)
 import System.IO.Error
 import System.IO.Temp
 import Text.HTML.TagSoup (renderTagsOptions, RenderOptions(..), Tag(..),
@@ -677,7 +674,8 @@ readDefaultDataFile "reference.odt" =
 readDefaultDataFile fname =
 #ifdef EMBED_DATA_FILES
   case lookup (makeCanonical fname) dataFiles of
-    Nothing       -> err 97 $ "Could not find data file " ++ fname
+    Nothing       -> E.throwIO $ PandocAppError 97 $
+                        "Could not find data file " ++ fname
     Just contents -> return contents
   where makeCanonical = Posix.joinPath . transformPathParts . splitDirectories
         transformPathParts = reverse . foldl go []
@@ -693,7 +691,7 @@ checkExistence fn = do
   exists <- doesFileExist fn
   if exists
      then return fn
-     else err 97 ("Could not find data file " ++ fn)
+     else E.throwIO $ PandocAppError 97 ("Could not find data file " ++ fn)
 #endif
 
 -- | Read file from specified user data directory or, if not found there, from
@@ -759,12 +757,6 @@ openURL u
 -- Error reporting
 --
 
-err :: MonadIO m => Int -> String -> m a
-err exitCode msg = liftIO $ do
-  UTF8.hPutStrLn stderr msg
-  exitWith $ ExitFailure exitCode
-  return undefined
-
 mapLeft :: (a -> b) -> Either a c -> Either b c
 mapLeft f (Left x) = Left (f x)
 mapLeft _ (Right x) = Right x