From c5e4ede1a46bfb6e669f98002ac69560ef088b2a Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Thu, 23 Jan 2025 17:35:23 +0530
Subject: [PATCH] fix: handle array unknown provided as `Symbol` to `remake`

---
 src/remake.jl                             | 5 ++++-
 test/downstream/modelingtoolkit_remake.jl | 8 ++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/remake.jl b/src/remake.jl
index 73d7634ef..4c8f20a97 100644
--- a/src/remake.jl
+++ b/src/remake.jl
@@ -910,7 +910,10 @@ function fill_vars(
         v === nothing && continue
         idx = index_function(prob, k)
         idx === nothing && continue
-        if !(idx isa AbstractArray) || symbolic_type(k) != ArraySymbolic()
+        # If `k` is an array symbolic, and `[:k => [1.0, 2.0]]` is provided
+        if idx isa AbstractArray && symbolic_type(k) == ScalarSymbolic()
+            k = [idx_to_vsym[i] for i in idx]
+        elseif !(idx isa AbstractArray) || symbolic_type(k) != ArraySymbolic()
             idx = (idx,)
             k = (k,)
             v = (v,)
diff --git a/test/downstream/modelingtoolkit_remake.jl b/test/downstream/modelingtoolkit_remake.jl
index 1797c5604..677a48a79 100644
--- a/test/downstream/modelingtoolkit_remake.jl
+++ b/test/downstream/modelingtoolkit_remake.jl
@@ -424,3 +424,11 @@ end
     @test eltype(initprob.u0) <: ForwardDiff.Dual
     @test eltype(SciMLStructures.canonicalize(SciMLStructures.Tunable(), initprob.p)[1]) <: ForwardDiff.Dual
 end
+
+@testset "Array unknown specified as Symbol" begin
+    @variables x(t)[1:2]
+    @parameters k
+    @mtkbuild sys = ODESystem([D(x[1]) ~ k * x[1], D(x[2]) ~ - x[2]], t)
+    prob = ODEProblem(sys, [x => ones(2)], (0.0, 1.0), [k => 2.0])
+    prob2 = remake(prob; u0 = [:x => 2ones(2)])
+end