Pkg.project() returns nothing for name, uuid, version for package added via Pkg

[NHDaly]

This question regards the Pkg.project() feature, originally added in #385.

The package in question here is RAI.jl, which attempts to set its user agent for HTTP requests using the project version:
https://github.com/RelationalAI/rai-sdk-julia/blob/93b18be6d7d91385a0854330b5d3bd0fe28f4653/src/RAI.jl#L25-L26

When I clone this repo, and open it as a project via julia --proj, it works correctly, giving:

julia> using RAI

julia> RAI.PROJECT_VERSION
v"0.2.4"

julia> RAI._user_agent()
"rai-sdk-julia/0.2.4"

However, if I add the package to another project, or to my top-level environment, it gets nothing:

julia> using Pkg

julia> Pkg.add("RAI")

julia> using RAI

julia> RAI._user_agent()
"rai-sdk-julia/nothing"

julia> RAI.PROJECT_VERSION

You can see that this is returning nothing:

julia> @eval RAI Pkg.project()
Pkg.API.ProjectInfo(nothing, nothing, nothing, false, Dict{String, Base.UUID}("PProf" => UUID("e4faabce-9ead-11e9-39d9-4379958e3056"), "MethodAnalysis" => UUID("85b6ec6f-f7df-4429-9514-a64bcd9ee824"), "Memoize" => UUID("c03570c3-d221-55d1-a50c-7939bbd78826"), "Revise" => UUID("295af30f-e4ad-537b-8983-00126c2a3abe"), "BenchmarkTo
ols" => UUID("6e4b80f9-dd63-53aa-95a3-0cdb28fa8baf"), "Cthulhu" => UUID("f68482b8-f384-11e8-15f7-abe071a5a75f"), "RAI" => UUID("9c30249a-7e08-11ec-0e99-a323e937e79f"), "LookingGlass" => UUID("1fcbbee2-b350-4a01-aad8-439064dba09e"), "CloudStore" => UUID("3365d9ee-d53b-4a56-812d-5344d5b716d7")), "/Users/nathandaly/.julia/environme
nts/v1.8/Project.toml")

julia> @eval RAI Pkg.project().version

julia>

I see in #3267 that this is an experimental feature.

Should we not be using it like this?

Thank you!