Add set_preferences!(name::String, ...) method which pulls UUID from Project.toml

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
+    uuid = get_uuid(name)
+    if uuid === nothing
+        throw(ArgumentError("Cannot resolve package '$(name)' in load path; have you added the package as a top-level dependency?"))
+    end
+    return set_preferences!(uuid, prefs...; kwargs...)
+end
 
 """
     @set_preferences!(prefs...)

src/utils.jl

@@ -52,22 +52,47 @@
     end
 end
 
-function find_first_project_with_uuid(uuid::UUID)
-    # Find first element in `Base.load_path()` that contains this UUID
-    # This code should look similar to the search in `Base.get_preferences()`
+function load_path_walk(f::Function)
     for env in Base.load_path()
         project_toml = Base.env_project_file(env)
         if !isa(project_toml, String)
             continue
         end
 
+        ret = f(project_toml)
+        if ret !== nothing
+            return ret
+        end
+    end
+    return nothing
+end
+
+function get_uuid(name::String)
+    return load_path_walk() do project_toml
+        project = Base.parsed_toml(project_toml)
+        if haskey(project, "uuid") && get(project, "name", "") == name
+            return project["uuid"]
+        end
+        for key in ["deps", "extras"]
+            if haskey(project, key) && haskey(project[key], name)
+                return parse(Base.UUID, project[key][name])
+            end
+        end
+        return nothing
+   end
+end
+
+function find_first_project_with_uuid(uuid::UUID)
+    # Find first element in `Base.load_path()` that contains this UUID
+    # This code should look similar to the search in `Base.get_preferences()`
+    return load_path_walk() do project_toml
         # Check to see if this project has a name mapping
         pkg_name = Base.get_uuid_name(project_toml, uuid)
         if pkg_name !== nothing
             return (project_toml, pkg_name)
         end
+        return nothing
     end
-    return (nothing, nothing)
 end
 
 # Drop any nested `__clear__` keys:

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.