From 75588648785834905e2cb698a7d75174d178f435 Mon Sep 17 00:00:00 2001
From: Anthony Costarelli <acostare@nrel.gov>
Date: Tue, 2 Jun 2026 10:53:53 -0400
Subject: [PATCH] strip_module_name: handle UnionAll component types

PSY6 parameterized some component families on a unit system (e.g.
ReserveDemandCurve{ReserveUp} is now ReserveDemandCurve{ReserveUp, U} where U),
making the partially-applied type a UnionAll. The @generated Type method read
T.parameters, which only exists on DataType, so it threw a FieldError on these
types. Unwrap the UnionAll and drop the free TypeVars, keeping the bound
parameters so the stripped name stays unique (e.g. "ReserveDemandCurve{ReserveUp}").

This lets downstream consumers (IOM container-key encoding) drop their local
UnionAll workaround.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 src/utils/utils.jl | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/utils/utils.jl b/src/utils/utils.jl
index b37b6f656..c6689cda8 100644
--- a/src/utils/utils.jl
+++ b/src/utils/utils.jl
@@ -187,11 +187,18 @@ julia> strip_module_name(VariableReserve{PowerSystems.ReserveUp})
         # Fall back to string method for Union types
         return :(strip_module_name(string(T)))
     end
-    name = string(nameof(T))
-    if isempty(T.parameters)
+    # A partially-applied parameterized type (e.g. `ReserveDemandCurve{ReserveUp}` when the
+    # type carries a further free parameter such as a unit system) is a `UnionAll` and has
+    # no `.parameters`. Unwrap it and drop the free `TypeVar`s, keeping the bound parameters
+    # so the stripped name stays unique on those (e.g. "ReserveDemandCurve{ReserveUp}").
+    base = T isa UnionAll ? Base.unwrap_unionall(T) : T
+    name = string(nameof(base))
+    params = filter(p -> !(p isa TypeVar), collect(base.parameters))
+    if isempty(params)
         return name
     else # I believe there's only 2 parameters, so slightly overkill.
-        param_names = join([string(nameof(p)) for p in T.parameters], ", ")
+        param_names =
+            join([p isa Type ? string(nameof(p)) : string(p) for p in params], ", ")
         return name * "{" * param_names * "}"
     end
 end