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haskellyesodconduit

Yesod respondSource from source that has PrimMonad constraint

I am working on a website using Yesod and am trying to stream a file from a zip archive into the HTTP response.

I choose the zip package, the relevant function is getEntrySource.

It returns a

ConduitT () ByteString m ()

where m has to satisfy

  • PrimMonad m
  • MonadThrow m
  • MonadResource m

One type that would fit those constraints would be ResourceT IO

In order to stream data Yesod provides the respondSource function that takes a

ConduitT () (Flush Builder) (HandlerFor site) ()

My Problem is:

  • ResourceT IO would work for getEntrySource but respondSource expects a HandlerFor site. I found the transPipe function but I don't think unwrapping the ResourceT IO and wrapping every chunk in a HandlerFor site is what I want.

  • HandlerFor site isn't an instance of PrimMonad and I don't grasp PrimMonad enough to judge whether it would even make sense for it to be.

Solution

  • Looks like a pure oversight that HandlerFor isn't an instance of PrimMonad. I've pushed a commit that should address this, and will release to Hackage once CI tells me it's safe.