[Haskell-cafe] Conduit Error Output: Control.Monad.Trans.Resource.stateCleanup

[Lyndon Maydwell]

Hi Michael, Café.

I'm writing some code using the conduit library and am encountering
the following error output (while the program appears to function
correctly) when using Data.Conduit.Lazy.

The error given is:

> profile_simple_test_data: Control.Monad.Trans.Resource.stateCleanup: There is a bug in the implementation. The mutable state is being accessed after cleanup. Please contact the maintainers.

A reduced code snippet that generates this error is (also attached):

> import Control.Monad
> import System.Environment
> import Control.Monad.IO.Class (liftIO)
> import System.IO
> import Data.Conduit.Lazy
> import Data.List (sort)
>
> import Data.Conduit
>
> import Prelude hiding (map)
>
> main = getArgs >>= process
>
> process args = mapM_ sorted args
>
> sorted x = runResourceT (lazyConsume $ sourceFeed x) >>= (mapM_ print . id)
>
> sourceFeed :: ResourceIO m => FilePath -> Source m String
> sourceFeed file = sourceIO
>     (openFile file ReadMode)
>     hClose
>     (\h -> liftIO $ do
>         eof <- hIsEOF h
>         if eof
>             then return IOClosed
>             else fmap IOOpen $ hGetLine h)

when run over any text file.

I may be doing something inconsistent with the correct use of sourceIO
or lazyConsume, however, I tried to follow the example at
http://www.yesodweb.com/home/snoyberg/blogs/conduit/conduit/source/source.ditamap?nav=nav-2
as closely as possible.

Is this a bug, or simply an incorrect use of Conduit?
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