How can I downgrade a package?

[lippling]

Hi,

I have problems with the tls package and want to downgrade it from 1.3.1 to 1.2.17. How can I do that?

I have the following files:

haskell-apns.cabal:

build-depends: [...]
               , tls == 1.2.17  -- I tried to pin down the version, originally there was no version constraint
               [...]

stack.yaml:

packages:
- '.'
extra-deps: ["tls-1.2.17", "x509-validation-1.5.2", "x509-1.5.1", "x509-store-1.5.0"]
resolver: nightly-2015-07-19

1.2.17 is built, but 1.3.1 is used and e.g. stack ghci or stack unpack use 1.3.1.

Any ideas?

PS: I use stack: Version 0.1.2.1, Git revision 500a55336af2245d2bcb3ed4201b126a030088c7, but I also tried 0.1.2.0.

[DanBurton]

How odd. I just want to confirm that your expectations are correct, and this is indeed a bug.

[lippling]

Is there anything I could do as a workaround until the bug ist fixed?

[DanBurton]

As a workaround, you could try using resolver: ghc-7.10 and then specifying explicit versions for all of your dependencies in extra-deps.

[DanBurton]

Pinging @chrisdone and @snoyberg to draw attention to this bug; I remember commenting on related code a while ago and thought it was fixed since then.

[snoyberg]

I was just looking this over. I think there are two different issues at play:

1. stack unpack ignores all version constraints in the stack.yaml file. This is actually by design: stack unpack is not a project level command, and therefore does not use project settings. This may be confusing, but is designed to work in the same way as the cabal unpack command. You can give it an explicit version via stack unpack foo-1.2.3
2. stack ghci allows GHC itself to choose the versions of packages, and unfortunately GHC's shadowing algorithm is not working the way we want. It seems like stack ghci needs to be explicit about which package versions/IDs it's using, likely by passing in -package flags. I believe you can work around this with something like stack exec -- ghci -package foo-1.2.3.

Am I reading correctly that these are the two issues being reported?

[lippling]

@snoyberg you are right. stack build works and stack exec -- ghci -package tls-1.2.17 also seems to work. Why does stack ghci --package tls-1.2.17 not work?

Thanks!

[snoyberg]

Because of what I mentioned above: the stack ghci command is not passing any -package flags to ghci (though it probably should). --package is just telling stack to make sure that that package is installed, but that information is not being communicated to GHCi in any way.

[lippling]

Ok, thanks for the clarfication.

[snoyberg]

I've opened up #678 to track the necessary changes to stack ghci. I believe that covers everything, so I'll close this out.