Add set_preferences!(name::String, ...) method which pulls UUID fro…

…m `Project.toml`

This makes it much more convenient to set preferences as previously you
either had to know (1) the `UUID` or (2) have the `Module` handy, and
sometimes you don't want to load an entire package just to set a
preference for it.

src/Preferences.jl

@@ -285,6 +285,14 @@ end
 function set_preferences!(m::Module, prefs::Pair{String,<:Any}...; kwargs...)
  return set_preferences!(get_uuid(m), prefs...; kwargs...)
 end
+function set_preferences!(name::String, prefs::Pair{String,<:Any}...; kwargs...)
+ # Look up UUID
+ pkg_and_path = Base.identify_package_env(name)
+ if pkg_and_path === nothing
+ throw(ArgumentError("Cannot resolve package '$(name)' in load path; have you added the package as a top-level dependency?"))
+ end
+ return set_preferences!(pkg_and_path[1].uuid, prefs...; kwargs...)
+end
 
 """
  @set_preferences!(prefs...)

test/runtests.jl

@@ -154,6 +154,26 @@ up_path = joinpath(@__DIR__, "UsesPreferences")
  end
 end
 
+@testset "Loading UUID from Project.toml" begin
+ with_temp_depot() do; mktempdir() do dir
+ activate(dir) do
+ push!(Base.LOAD_PATH, dir)
+ try
+ # Can't do this unless `UsesPreferences` is added as a dep
+ @test_throws ArgumentError Preferences.set_preferences!("UsesPreferences", "location" => "exists")
+
+ Pkg.develop(;path=up_path)
+
+ # After `dev`'ing `up_path`, it works.
+ Preferences.set_preferences!("UsesPreferences", "location" => "exists")
+ @test load_preference(up_uuid, "location") == "exists"
+ finally
+ pop!(Base.LOAD_PATH)
+ end
+ end
+ end; end
+end
+
 # Load UsesPreferences, as we need it loaded to satisfy `set_preferences!()` below,
 # otherwise it can't properly map from a UUID to a name when installing into a package
 # that doesn't have UsesPreferences added yet.