Where can I find correct package name and version for Haskell?

Question

Say, I need System.Eval.Haskell. Or whatever else. How do I know which package I should specify in my package.yaml? When I go to the https://hackag

Answer 1

Say, I need System.Eval.Haskell. Or whatever else. How do I know which package I should specify in my package.yaml?

There may be many packages which export a particular module, so you can't necessarily know which package to import from the module name. But generally it's obvious from a google search.

As duplode mentions the package is named plugins, and as you found out stack uses the - format to specify a package name + version in the stack.yaml. Cabal uses a different format, which is more flexible (can specify fuzzy package version ranges, etc.). Since stack works on fixed snapshots of package versions, the plugins-1.5.7 format is sufficient.

When you write plugins in your *.cabal file, you're specifying something like "any version of plugins but prefer the most recent". But because your package repository is limited to a particular snapshot by stack what you're really doing is letting stack manage your dependencies.