Etlas doesn't seem to use latest version of package

[AlexeyRaga]

State

I have the following packages currently published for eta:

eta-kafka-client-0.5.0
eta-kafka-client-0.5.1
eta-kafka-conduit-0.5.0
eta-kafka-conduit-0.5.1

They are registered in https://github.com/typelead/etlas-index/tree/master/packages

Steps

In a new Eta project (etlas init):

1. reference both packages in .cabal without specifying the version :

  build-depends:        base >=4.8 && <4.9
                      , eta-kafka-client
                      , eta-kafka-conduit

2. etlas update

3. etlas install --dependencies only

Resolving dependencies...
Configuring eta-kafka-conduit-0.5.1...
Building eta-kafka-conduit-0.5.1...
Failed to install eta-kafka-conduit-0.5.1
Build log ( /Users/araga/.etlas/logs/eta-0.0.9.1/eta-kafka-conduit-0.5.1-6voahL7UFAK6qLtkfQzOuM.log ):
etlas: Entering directory '/var/folders/3x/l50y6rts50j_9jqyp0fl7lqh0000gn/T/etlas-tmp-87470'
Configuring eta-kafka-conduit-0.5.1...
Preprocessing library for eta-kafka-conduit-0.5.1..
Building library for eta-kafka-conduit-0.5.1..
[1 of 3] Compiling Kafka.Conduit.Source ( src/Kafka/Conduit/Source.hs, dist/build/Kafka/Conduit/Source.jar )

src/Kafka/Conduit/Source.hs:27:34:
    Couldn't match type ‘ghc-prim-0.4.0.0:GHC.CString.JByteArray’
                   with ‘ByteString’

This happens because etlas correctly chooses the latest version of eta-kafka-conduit (0.5.1), but for kafka-client it solves version 0.5.0 instead of the latest.

I did have 0.5.0 it etlas install'ed before, and I see it in my ~/.etlas/packages/etlas.typelead.com, but version 0.5.1 is not there despite etlas update.

So etlas somehow chooses to ignore newer version in favour of an oldest one.

Expected behaviour

I expected that etlas finds out and uses the latest version of the package when no constraints are specified in .cabal (up to etlas update time).

Workaround

Specifying constraints in .cabal helps:

  build-depends:        base >=4.8 && <4.9
                      , eta-kafka-client > 0.5.0
                      , eta-kafka-conduit > 0.5.0

[rahulmutt]

The default behaviour is to use the latest version that is installed already, as long as it matches the existing constraints. Do you think it may be better to have it automatically upgrade the package instead?

[rahulmutt]

One way to get the behaviour you want is to use the --allow-newer flag when you install. In fact, I really want to make this flag a default since it just makes dependency resolution a whole lot simpler.