fix missing uuid check on extension when finding the location of an extension

in stacked environments with name collisions of extensions this could compute the path for the wrong extension

Author: KristofferC

base/loading.jl

@@ -694,7 +694,7 @@ function manifest_uuid_path(env::String, pkg::PkgId)::Union{Nothing,String,Missi
             # if `pkg` matches the project, return the project itself
             return project_file_path(project_file, pkg.name)
         end
-        mby_ext = project_file_ext_path(project_file, pkg.name)
+        mby_ext = project_file_ext_path(project_file, pkg)
         mby_ext === nothing || return mby_ext
         # look for manifest file and `where` stanza
         return explicit_manifest_uuid_path(project_file, pkg)
@@ -709,7 +709,7 @@ function manifest_uuid_path(env::String, pkg::PkgId)::Union{Nothing,String,Missi
             if parent_project_file !== nothing
                 parentproj = project_file_name_uuid(parent_project_file, parentid.name)
                 if parentproj == parentid
-                    mby_ext = project_file_ext_path(parent_project_file, pkg.name)
+                    mby_ext = project_file_ext_path(parent_project_file, pkg)
                     mby_ext === nothing || return mby_ext
                 end
             end
@@ -725,13 +725,13 @@ function find_ext_path(project_path::String, extname::String)
     return joinpath(project_path, "ext", extname * ".jl")
 end
 
-function project_file_ext_path(project_file::String, name::String)
+function project_file_ext_path(project_file::String, ext::PkgId)
     d = parsed_toml(project_file)
     p = dirname(project_file)
     exts = get(d, "extensions", nothing)::Union{Dict{String, Any}, Nothing}
     if exts !== nothing
-        if name in keys(exts)
-            return find_ext_path(p, name)
+        if ext.name in keys(exts) && ext.uuid == uuid5(UUID(d["uuid"]::String), ext.name)
+            return find_ext_path(p, ext.name)
         end
     end
     return nothing
@@ -834,9 +834,7 @@ function implicit_env_project_file_extension(dir::String, ext::PkgId)
     for pkg in readdir(dir; join=true)
         project_file = env_project_file(pkg)
         project_file isa String || continue
-        proj = project_file_name_uuid(project_file, "")
-        uuid5(proj.uuid, ext.name) == ext.uuid || continue
-        path = project_file_ext_path(project_file, ext.name)
+        path = project_file_ext_path(project_file, ext)
         if path !== nothing
             return path, project_file
         end

test/loading.jl

@@ -1630,3 +1630,16 @@ end
         copy!(LOAD_PATH, old_load_path)
     end
 end
+
+@testset "extension path computation name collision" begin
+    old_load_path = copy(LOAD_PATH)
+    try
+        empty!(LOAD_PATH)
+        push!(LOAD_PATH, joinpath(@__DIR__, "project", "Extensions", "ExtNameCollision_A"))
+        push!(LOAD_PATH, joinpath(@__DIR__, "project", "Extensions", "ExtNameCollision_B"))
+        ext_B = Base.PkgId(Base.uuid5(Base.identify_package("ExtNameCollision_B").uuid, "REPLExt"), "REPLExt")
+        @test Base.locate_package(ext_B) == joinpath(@__DIR__, "project",  "Extensions", "ExtNameCollision_B", "ext", "REPLExt.jl")
+    finally
+        copy!(LOAD_PATH, old_load_path)
+    end
+end