[Haskell-cafe] cannot catch exception

[David Fox]

This fixes it by forcing the evaluation of the decode where it can be
caught:

return $ Right $! TE.decodeUtf8 bufferStrict

or

Right <$> evaluate (TE.decodeUtf8 bufferStrict)



On Mon, Mar 4, 2019 at 3:50 AM Kees Bleijenberg <K.Bleijenberg at lijbrandt.nl>
wrote:

> Hi all,
>
>
>
> The program reads lots of small Text files. readCDFile handles the
> encoding. Below is the simplest version of readCDFile.
>
> If I call readCDFile "/home/kees/freeDB/inputError/" "blah" (the file blah
> does not exist) I get:
>
> Left "MyError: /home/kees/freeDB/inputError/blah: openBinaryFile: does not
> exist (No such file or directory)". The exception is caught by
> exceptionHandler
>
> If I call readCDFile "/home/kees/freeDB/inputError/" "67129209" I get
> freeDB: Cannot decode byte '\xa0': Data.Text.Internal.Encoding.decodeUtf8:
> Invalid UTF-8 stream. The exception is not caught by exceptionHandler (No
> “MyError: ” in front). The file 67129209 is indeed bad encoded.
>
> I’am using SomeException. Still, this ‘bad encoding exception’ is not
> caught. Why?
>
>
>
> Kees
>
>
>
> import qualified Data.Text as T
>
> import System.FilePath.Posix
>
> import qualified Data.Text.Encoding as TE
>
> import qualified Data.ByteString.Lazy as B
>
> import Prelude hiding (catch)
>
> import Control.Exception
>
>
>
> main :: IO ()
>
> main = do
>
>           res <- readCDFile "/home/kees/freeDB/inputError/" "67129209"
>
>           print res
>
>
>
> readCDFile :: FilePath -> FilePath -> IO (Either String T.Text)
>
> readCDFile baseDir fn = do
>
>   catch ( do
>
>             buffer <- B.readFile (combine baseDir fn)
>
>             let bufferStrict = B.toStrict buffer
>
>             return $ Right $ TE.decodeUtf8 bufferStrict
>
>          ) exceptionHandler
>
>
>
> exceptionHandler :: SomeException -> IO (Either String T.Text)
>
> exceptionHandler e = do let err = show e
>
>                         return $ Left $ "MyError: " ++ err
>
>
>
>
>
>
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> Virusvrij.
> www.avast.com
> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
> <#m_4240515626836095125_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20190304/6844815c/attachment.html>