fix: fix parameter object aliasing after remake

Author: AayushSabharwal

src/systems/nonlinear/initializesystem.jl

@@ -512,9 +512,10 @@ end
 
 function SciMLBase.late_binding_update_u0_p(
         prob, sys::AbstractSystem, u0, p, t0, newu0, newp)
-    u0 === missing && return newu0, newp
-    eltype(u0) <: Pair || return newu0, newp
+    u0 === missing && return newu0, (p === missing ? copy(newp) : newp)
+    eltype(u0) <: Pair || return newu0, (p === missing ? copy(newp) : newp)
 
+    newp = p === missing ? copy(newp) : newp
     newu0 = DiffEqBase.promote_u0(newu0, newp, t0)
     tunables, repack, alias = SciMLStructures.canonicalize(SciMLStructures.Tunable(), newp)
     tunables = DiffEqBase.promote_u0(tunables, newu0, t0)

test/initializationsystem.jl

@@ -1370,3 +1370,21 @@ end
     @test_nowarn remake(prob, p = [p => 1.0])
     @test_nowarn remake(prob, p = [p => ForwardDiff.Dual(1.0)])
 end
+
+@testset "`late_binding_update_u0_p` copies `newp`" begin
+    @parameters k1 k2
+    @variables X1(t) X2(t)
+    @parameters Γ[1:1]=missing [guess = [1.0]]
+    eqs = [
+        D(X1) ~ k1 * (Γ[1] - X1) - k2 * X1
+    ]
+    obs = [X2 ~ Γ[1] - X1]
+    @mtkbuild osys = ODESystem(eqs, t, [X1, X2], [k1, k2, Γ]; observed = obs)
+    u0 = [X1 => 1.0, X2 => 2.0]
+    ps = [k1 => 0.1, k2 => 0.2]
+
+    oprob1 = ODEProblem(osys, u0, 1.0, ps)
+    oprob2 = remake(oprob1, u0 = [X1 => 10.0])
+    integ1 = init(oprob1)
+    @test integ1[X1] ≈ 1.0
+end