stackage-curator should throw an error if a package name is mistyped or otherwise non-existent

[sjakobi]

I noticed that stackage-curator currently simply ignores a non-existent package name here.

I'd be interested in submitting a PR to fix this but I'm unfamiliar with the code base and unsure where to add such a check. I guess it should happen soon after parsing the build-constraints.yaml file.

[snoyberg]

This is a great idea, thanks for bringing it up. I believe the right place to start is the Stackage.BuildPlan.newBuildPlan function. That function takes a BuildConstraints value (which represents everything in the build-constraints.yaml) and combines it with the actual package index information to create a BuildPlan. It appears that we should additionally collect a Set of all PackageNames referenced, remove all such package names seen in the index, and then raise an error if any are left over.

That's a guess on my part, is that enough of a pointer in the (hopefully) right direction?

[sjakobi]

Thanks! Your pointer was perfect! :)