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Add API for exceptional error conditions #25

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merged 2 commits into from
Nov 25, 2019
Merged

Add API for exceptional error conditions #25

merged 2 commits into from
Nov 25, 2019

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serras
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@serras serras commented Nov 25, 2019

Following a meeting with @kutyel and @pepegar, we have drafted an API for exceptional conditions in mu-haskell (errors like not found or not implemented).

  • We follow the design of both Servant and Mu, that is, and make the servers return ExceptT ServerError IO a instead of plain IO a as before.
  • To make simple server unaware of the extra ExceptT layer, there's an alwaysOk function which lifts a simple handler in IO to work on ExceptT ServerError IO.

This PR implements that API and updates the examples to use it.

Comments are welcome. The main paint points are:

  • Conduits also have to be upgraded to use those monad transformers (do they? maybe we can make them unaware of external errors, but this does not seam real...)
  • You have to sprinkle the alwaysOk here and there.

@serras serras requested a review from kutyel November 25, 2019 11:44
pepegar
pepegar reviewed Nov 25, 2019
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Just added a comment, apart of that, it looks awesome. Great job @serras !

core/rpc/src/Mu/Server.hs Outdated Show resolved Hide resolved
kutyel
kutyel approved these changes Nov 25, 2019
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Looks good to me, awesome work! 🙌

examples/todolist/src/Server.hs
todos <- liftIO $ readTVarIO t
case find (getMsg idMsg) todos of
Just todo -> pure $ TodoListResponse todo
Nothing -> serverError $ ServerError NotFound "unknown todolist id"
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👀 This looks good, thanks for adding it! 👏

@serras serras merged commit 7674ef0 into master Nov 25, 2019
@serras serras deleted the errors branch November 25, 2019 13:12
kutyel pushed a commit that referenced this pull request Jan 4, 2022
@serras
Add API for exceptional error conditions (#25)
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@kutyel kutyel kutyel approved these changes

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3 participants
@serras @pepegar @kutyel