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Add more general version of onException #3119

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jerbaroo wants to merge 2 commits into from
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Add more general version of onException #3119

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bb006f2
Add onExceptionE
jerbaroo Jul 25, 2025
19b8ba8
Avoid duplication
jerbaroo Jul 25, 2025
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1 change: 1 addition & 0 deletions core/src/Streamly/Data/Stream.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -639,6 +639,7 @@ module Streamly.Data.Stream
-- stream of arrays before flattening it to a stream of chars.
--
, onException
, onExceptionE
, handle

-- * Resource Management
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10 changes: 8 additions & 2 deletions core/src/Streamly/Internal/Data/Stream/Exception.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@ module Streamly.Internal.Data.Stream.Exception

-- * Exceptions
, onException
, onExceptionE
, ghandle
, handle
)
Expand Down Expand Up @@ -280,11 +281,16 @@ afterIO action (Stream step state) = Stream step' Nothing
--
{-# INLINE_NORMAL onException #-}
onException :: MonadCatch m => m b -> Stream m a -> Stream m a
onException action stream =
onException action = onExceptionE $
\(e :: MC.SomeException) -> action >> MC.throwM e

{-# INLINE_NORMAL onExceptionE #-}
onExceptionE :: (Exception e, MonadCatch m) => (forall b. e -> m b) -> Stream m a -> Stream m a
onExceptionE onE stream =
gbracket_
(return ()) -- before
return -- after
(\_ (e :: MC.SomeException) _ -> action >> MC.throwM e)
(\_ e _ -> onE e)
(inline MC.try)
(const stream)

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