You can force this with cabal using --constraint "persistent-template=2.2.2" or the equivalent.

But these kinds of dependency solving problems are the primary reason I recommend using a Stackage snapshot[1]. If you switch over to building with Stack[2], you'll get that behavior by default.

[1] https://www.stackage.org/
[2] http://haskellstack.org/

On Wed, Mar 2, 2016 at 12:04 PM, Miro Karpis <miroslav.karpis@gmail.com> wrote:
Please,..can you help me with following?

I'm trying to install both persistent-postgresql together with persistent-template, but I keep getting:


mac:~ miro$ cabal install persistent-template
Resolving dependencies...
In order, the following would be installed:
aeson-0.9.0.1 (latest: 0.11.0.0) (via: persistent-template-2.1.5 persistent-2.2.4 aeson-compat-0.3.1.0) (new version)
aeson-compat-0.3.1.0 (via: persistent-template-2.1.5) (new package)
persistent-2.2.4 (via: persistent-template-2.1.5) (reinstall) (changes: aeson-0.11.0.0 -> 0.9.0.1)
persistent-template-2.1.5 (new package)
cabal: The following packages are likely to be broken by the reinstalls:
persistent-postgresql-2.2.2
Use --force-reinstalls if you want to install anyway.



If I continue with force-reinstall then I broke postgresql. Is there a way to force persistent-template to use 2.2.2 version (I know if I download it and change the dep. in cabal file,....but is that what I should do :) )?



running on:
mac:~ miro$ cabal --version
cabal-install version 1.22.8.0
using version 1.22.7.0 of the Cabal library

mac:~ miro$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.10.3



cheers,
m.



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