Stack init could accept explicit versions

[ndmitchell]

For my test suite, I run things like hlint through stack init then stack build. At the moment, haskell-src-exts is not correct in the latest lts, so stack init fails. I would like to do:

stack init --resolver "haskell-src-exts-1.17.0"

Whether resolver takes package names, or I use --extra haskell-src-exts-1.17.0 doesn't matter, but it would be nice to init with explicit constraints for when stack otherwise fails.

[mgsloan]

Makes sense! --package haskell-src-exts-1.17.0 would be consistent with stack ghci's CLI. I'm in favor of such an addition.

[harendra-kumar]

With the changes in pull request #1583 you can achieve this by putting your preferred resolver in stack.yaml and haskell-src-exts-1.17.0 in extra-deps and then using stack solver.

[ndmitchell]

@harendra-kumar - that doesn't help if I don't have a stack.yaml already, and here my use case is stack init to create the stack.yaml.

[mgsloan]

You can, however do stack init --force, and then add haskell-src-exts-1.17.0 to your extra-deps.

To me, this seems to handle the usecase nicely. I wouldn't be opposed to adding a --package flag if you still think it's needed and if it's easy to implement.

[ndmitchell]

As soon as it involves the step "edit the stack.yaml" then it's no longer really suitable for running automatically on a buildbot for my use case, and I'd have to go and create a manual stack file, which is a bit of a shame. But maybe that's not a use case you support.

[harendra-kumar]

At the moment, haskell-src-exts is not correct in the latest lts, so stack init fails.

#1583 does everything possible to make stack init succeed. With that merged you can just use stack init --solver and it should give you a working stack.yaml with a snapshot resolver and haskell-src-exts in extra-deps. You can also use stack init --solver --resolver if you want to init with a specific resolver.

[ndmitchell]

Ah, awesome :) - in that case I think there is enough to consider this fixed.