There are two different approaches you could use:

1. Modify the source so that its base monad is ResourceT IO. You can do that using hoist, e.g.:

let newSource = hoist lift (requestBody req)

2. In a situation like this, you don't really need ResourceT at all. Instead, using withFile and sinkHandle would be sufficient:

withFile ("source" </> fromText name) WriteMode $ \h ->

requestBody req $$ sinkHandle h

I'd recommend going for (2), as IMO it's a little bit clearer what's going on, and is slightly more efficient.

Michael

On Sun, Dec 8, 2013 at 9:44 PM, Leif Warner <abimelech@gmail.com> wrote:

Trying to upgrade this code from WAI 1.4.1 to 2.0.0. On one hand, I don't have to liftIO the IO action on line 23 anymore. On the other, this line that writes the request body to a file seems to be giving me some trouble now:

https://github.com/LeifW/online-typechecker/blob/master/index.hs#L22

No instance for (MonadResource IO) arising from a use of `sinkFile'

Possible fix: add an instance declaration for (MonadResource IO)
In the second argument of `($$)', namely
`sinkFile ("sources" </> fromText name)'
In a stmt of a 'do' block:

requestBody req $$ sinkFile ("sources" </> fromText name)

If I put a "runResouceT" in front of that, like "runResourceT $ requestBody req $$ sinkFile ("sources" </> fromText name)", I get

Couldn't match type `IO' with `ResourceT IO'
Expected type: Data.Conduit.Internal.Source
(ResourceT IO) Data.ByteString.Internal.ByteString

Actual type: Data.Conduit.Internal.Source
IO Data.ByteString.Internal.ByteString
In the return type of a call of `requestBody'
In the first argument of `($$)', namely `requestBody req'

In the second argument of `($)', namely
`requestBody req $$ sinkFile ("sources" </> fromText name)'

Any pointers?

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