Requesting better error message for non-packages

I just accidentally attempted to put a DrWatson project into my registry and spent a while figuring out why it wouldn't work. The stated error is that check_version! doesn't work on nothing (see below). That makes sense because a project isn't a package, and so doesn't have a version number. It doesn't make sense to put a non-package into a registry so this should fail, but I would prefer a better error message so that no one wastes the half hour I just wasted.

My suggestion is that when the UUID is loaded, if it's nothing immediately error with the message Project.toml has no UUID. Is $(package_name) a package? This makes sense to me because all packages need UUIDs.

I'm happy to make the PR this weekend.

julia> register("./NeonateTriCorr", registry = "SmithThesisRegistry")
┌ Info: Registering package
│   package_path = "/home/graham/git/NeonateTriCorr"
│   registry_path = "/home/graham/.julia/registries/SmithThesisRegistry"
│   package_repo = "https://github.com/grahamas/NeonateTriCorr.git"
│   uuid = nothing
│   version = nothing
│   tree_hash = "acebe5e97e155b073082cd8e6939ba74dc50e4c0"
└   subdir = ""
HEAD is now at 1601a1b New package: TriCorrApplications v0.2.0
Removing N/NeonateTriCorr/
Already on 'main'
Your branch is up to date with 'origin/main'.
ERROR: MethodError: no method matching check_version!(::Nothing, ::Vector{VersionNumber}, ::RegistryTools.ReturnStatus)
Closest candidates are:
  check_version!(::VersionNumber, ::Vector{VersionNumber}, ::RegistryTools.ReturnStatus) at ~/.julia/packages/RegistryTools/Epat9/src/register.jl:183
Stacktrace:
 [1] check_versions!(pkg::Pkg.Types.Project, versions_data::Dict{String, Any}, status::RegistryTools.ReturnStatus)
   @ RegistryTools ~/.julia/packages/RegistryTools/Epat9/src/register.jl:371
 [2] check_and_update_registry_files(pkg::Pkg.Types.Project, package_repo::String, tree_hash::SubString{String}, registry_path::String, registry_deps_paths::Vector{String}, status::RegistryTools.ReturnStatus; subdir::String)
   @ RegistryTools ~/.julia/packages/RegistryTools/Epat9/src/register.jl:575
 [3] do_register(package::String, registry::String; commit::Bool, push::Bool, branch::Nothing, repo::Nothing, ignore_reregistration::Bool, gitconfig::Dict{Any, Any}, create_gitlab_mr::Bool)
   @ LocalRegistry ~/.julia/packages/LocalRegistry/I8u9h/src/LocalRegistry.jl:247
 [4] do_register
   @ ~/.julia/packages/LocalRegistry/I8u9h/src/LocalRegistry.jl:156 [inlined]
 [5] #register#2
   @ ~/.julia/packages/LocalRegistry/I8u9h/src/LocalRegistry.jl:149 [inlined]
 [6] top-level scope
   @ REPL[6]:1

GunnarFarneback / LocalRegistry.jl

Requesting better error message for non-packages #60