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, 10 insertions, 1 deletions

diff --git a/src/Text/Pandoc/Error.hs b/src/Text/Pandoc/Error.hs
index 4b38348ac..252c469b1 100644
--- a/src/Text/Pandoc/Error.hs
+++ b/src/Text/Pandoc/Error.hs
@@ -37,9 +37,11 @@ module Text.Pandoc.Error (
 import Control.Exception (Exception)
 import Data.Generics (Typeable)
 import GHC.Generics (Generic)
-import Text.Pandoc.Shared (err)
 import Text.Parsec.Error
 import Text.Parsec.Pos hiding (Line)
+import qualified Text.Pandoc.UTF8 as UTF8
+import System.Exit (exitWith, ExitCode(..))
+import System.IO (stderr)
 
 type Input = String
 
@@ -49,6 +51,7 @@ data PandocError = PandocIOError String IOError
                  | PandocParseError String
                  | PandocParsecError Input ParseError
                  | PandocMakePDFError String
+                 | PandocAppError Int String
                  deriving (Show, Typeable, Generic)
 
 instance Exception PandocError
@@ -74,4 +77,10 @@ handleError (Left e) =
                         else ""
         in  err 65 $ "\nError at " ++ show  err' ++ errorInFile
     PandocMakePDFError s -> err 65 s
+    PandocAppError ec s -> err ec s
 
+err :: Int -> String -> IO a
+err exitCode msg = do
+  UTF8.hPutStrLn stderr msg
+  exitWith $ ExitFailure exitCode
+  return undefined