Update hackage-security to GHC 8.8

[Avi-D-coder]

This goes on top of #232

[Avi-D-coder]

Is MonadFail the right approach?

[bgamari]

Indeed this seems rather odd. I haven't looked at the surrounding code but it does seem suspicious that you would need to add a constraint of this form. Are you sure this is necessary?

[Avi-D-coder]

I'm not clear how MonadFail can be replaced, it seems to come from getCachedInfo:347 and ReadJSON_Keys_Layout comes from readLocalFile : 367.

Should I try to replace MonadFail with a Throws _?

[Avi-D-coder]

My mtl foo is not good enough to remove MonadFail ReadJSON_Keys_Layout.

@edsko I see you wrote the ReadJSON_Keys_Layout code, do you have any advice?

[Avi-D-coder]

THe cloest I have gotten is MonadError DeserializationError IO, but this produces the warning:

Security/Client.hs:211:18: warning:
    • Couldn't match type ‘IOException’ with ‘DeserializationError’
        arising from a functional dependency between:
          constraint ‘MonadError DeserializationError IO’
            arising from the type signature for:
                           checkForUpdates :: forall (down :: * -> *).
                                              (MonadError DeserializationError IO,
                                               Throws VerificationError, Throws SomeRemoteError) =>
                                              Repository down -> Maybe UTCTime -> IO HasUpdates
          instance ‘MonadError IOException IO’ at <no location info>
      Inaccessible code in
        a pattern with constructor: FGz :: Format FormatGz,
        in a case alternative
    • In the pattern: FGz
      In the pattern: Some FGz
      In a case alternative:
          Some FGz -> verifyFileInfo' (Just newInfoTarGz) targetPath tempPath

[bgamari]

In this case I would probably try to use the MonadError constraint to instead report a more precise error. For instance, define locally:

let lookupFile path =
      withExceptT DeserializationErrorSchema 
      $ liftEither $ FileMap.lookupM snapshotMeta path

and use this in place of FIleMap.lookupM below.

[Avi-D-coder]

I was not able to make this work (Either does not implement MonadFail) so I just wrote:

lookupErr :: MonadError e m => (String -> e) -> FileMap -> TargetPath -> m FileInfo

[hvr]

@Avi-D-coder to be honest, I'm utterly confused by this PR; is this really against master? Also this seems to address an issue that has long been resolved by 471a7b8, no?

[hvr]

This line here makes me suspect this is against some fairly ancient state of the master branch

[bgamari]

Hmm, indeed I am also a bit confused; master already appears to build with GHC 8.8.1. @Avi-D-coder, is there a particular error that you were seeing?

[Avi-D-coder]

This was based on #232