[Polysemy] Generalise and Move the Logger Effect to polysemy-wire-zoo

[mdimjasevic]

The PR generalises and moves the Logger effect from Spar into polysemy-wire-zoo.

Checklist

• The PR Title explains the impact of the change.
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[pcapriotti]

There is already a logger effect in polysemy-wire-zoo, which we use in galley and federator. Would it make sense to merge the two?

[mdimjasevic]

There is already a logger effect in polysemy-wire-zoo, which we use in galley and federator. Would it make sense to merge the two?

It crossed my mind and I was lazy to look at that. But you're right, this is a good opportunity to do that so I'll do it.

[isovector]

Looks good, but I'd suggest dropping discardTinyLogs

[isovector]

Why do you need this function?

[mdimjasevic]

This is to help GHC with type inference. If I don't use it, then GHC reports overlapping instances. An alternative is to use discardLogs @(Log.Msg -> Log.Msg) instead of discardTinyLogs.

[isovector]

That's surprising to me. Does the polysemy plugin help?

[mdimjasevic]

That's surprising to me. Does the polysemy plugin help?

It doesn't seem to. I tried this: 1) put the plugin as a GHC option in the cabal file and make its package a dependency, 2) use discardLogs instead of discardTinyLogs where I'm hoping the plugin would help, 3) observe I get the aforementioned error on overlapping instances, e.g.:

src/Federator/MockServer.hs:93:15: error:
    * Overlapping instances for Member
                                  (Wire.Sem.Logger.Logger
                                     (System.Logger.Message.Msg -> System.Logger.Message.Msg))
                                  '[Wire.Sem.Logger.Logger msg0, Embed IO]
        arising from a use of `runWaiErrors'
      Matching instances:
        two instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
      (The choice depends on the instantiation of `msg0'
       To pick the first instance above, use IncoherentInstances
       when compiling the other instance declarations)
    * In the second argument of `(.)', namely
        `runWaiErrors @'[ValidationError, ServerError, MockException]'
      In the second argument of `(.)', namely
        `discardLogs
           . runWaiErrors @'[ValidationError, ServerError, MockException]'
      In the expression:
        runM
          . discardLogs
              . runWaiErrors @'[ValidationError, ServerError, MockException]
   |
93 |             . runWaiErrors
   |               ^^^^^^^^^^^^...
cabal: Failed to build federator-1.0.0 (which is required by brig-2.0).

[mdimjasevic]

There is already a logger effect in polysemy-wire-zoo, which we use in galley and federator. Would it make sense to merge the two?

Done! I made the one that has been in Galley and Federator just a special case of the one I generalised from Spar.

[isovector]

lgtm