Can't install with stack

[JonathanReeve]

I'm a haskell beginner, and I'm trying to follow the instructions on the hakyll tutorial. I run these commands:

stack install hakyll
hackyll-init hackyll-test
cd hakyll-test
stack init
stack build
stack init site build

And that allows me to run Hakyll OK. But then if I run cabal install hakyll-sass as in the readme, it can't find the module, and I can't import it. Then if I try stack install hakyll-sass, I get these errors:

Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for hakyll-sass-0.2.3:
    aeson-pretty-0.7.2 must match >=0.8 (latest applicable is 0.8.5)

But if I try stack install aeson-pretty-0.8.5 I get the same error. I can't seem to install hakyll-sass in a way that hakyll (under stack) can see it.

[dunnl]

You're seeing this error because the resolver (package set) being used by stack for your project includes a version of aeson-pretty that conflicts with the dependencies of the hakyll-sass version you are trying to install. You get the same conflict when you try to install the latest version because it too conflicts with the older version (naturally).

One way to fix this is by modifying your stack.yaml file: change the resolver to lts-9.0 so that you are working with the latest package versions, including aeson-pretty-0.8.5. Then add hakyll-sass-0.2.3 to your extra-deps, because version 0.2.3 is not in the lts-9.0 resolver but it is on Hackage, so stack will get it from there.

Your issue might then be renamed "Version 0.2.3 is not on Stackage"

[JonathanReeve]

Great, thanks for this! Lawrence Dunn <[email protected]> writes:

…

You're seeing this error because the resolver (package set) being used by stack for your project includes a version of `aeson-pretty` that conflicts with the dependencies of the `hakyll-sass` version you are trying to install. You get the same conflict when you try to install the latest version because it too conflicts with the older version (naturally). One way to fix this is by modifying your stack.yaml file: change the resolver to `lts-9.0` so that you are working with the latest package versions, including `aeson-pretty-0.8.5`. Then add `hakyll-sass-0.2.3` to your extra-deps, because version 0.2.3 is not in the `lts-9.0` resolver but it is on Hackage, so stack will get it from there. Your issue might then be renamed "Version 0.2.3 is not on Stackage"