fix: fix initialization of DiscreteProblem(::JumpSystem)

Project.toml

@@ -123,7 +123,7 @@ NonlinearSolve = "4.3"
 OffsetArrays = "1"
 OrderedCollections = "1"
 OrdinaryDiffEq = "6.82.0"
-OrdinaryDiffEqCore = "1.13.0"
+OrdinaryDiffEqCore = "1.15.0"
 OrdinaryDiffEqDefault = "1.2"
 OrdinaryDiffEqNonlinearSolve = "1.3.0"
 PrecompileTools = "1"
@@ -132,7 +132,7 @@ RecursiveArrayTools = "3.26"
 Reexport = "0.2, 1"
 RuntimeGeneratedFunctions = "0.5.9"
 SCCNonlinearSolve = "1.0.0"
-SciMLBase = "2.68.1"
+SciMLBase = "2.71"
 SciMLStructures = "1.0"
 Serialization = "1"
 Setfield = "0.7, 0.8, 1"

src/systems/jumps/jumpsystem.jl

@@ -425,14 +425,15 @@ function DiffEqBase.DiscreteProblem(sys::JumpSystem, u0map, tspan::Union{Tuple,
         error("The passed in JumpSystem contains `Equation`s or continuous events, please use a problem type that supports these features, such as ODEProblem.")
     end
 
-    _, u0, p = process_SciMLProblem(EmptySciMLFunction, sys, u0map, parammap;
+    _f, u0, p = process_SciMLProblem(EmptySciMLFunction, sys, u0map, parammap;
         t = tspan === nothing ? nothing : tspan[1], use_union, tofloat = false, check_length = false)
     f = DiffEqBase.DISCRETE_INPLACE_DEFAULT
 
     observedfun = ObservedFunctionCache(
         sys; eval_expression, eval_module, checkbounds = get(kwargs, :checkbounds, false))
 
-    df = DiscreteFunction{true, true}(f; sys = sys, observed = observedfun)
+    df = DiscreteFunction{true, true}(f; sys = sys, observed = observedfun,
+        initialization_data = get(_f.kwargs, :initialization_data, nothing))
     DiscreteProblem(df, u0, tspan, p; kwargs...)
 end
 

src/systems/nonlinear/initializesystem.jl

@@ -13,7 +13,9 @@ function generate_initializesystem(sys::AbstractSystem;
         check_units = true, check_defguess = false,
         name = nameof(sys), extra_metadata = (;), kwargs...)
     eqs = equations(sys)
-    eqs = filter(x -> x isa Equation, eqs)
+    if !(eqs isa Vector{Equation})
+        eqs = Equation[x for x in eqs if x isa Equation]
+    end
     trueobs, eqs = unhack_observed(observed(sys), eqs)
     vars = unique([unknowns(sys); getfield.(trueobs, :lhs)])
     vars_set = Set(vars) # for efficient in-lookup

test/initializationsystem.jl

@@ -1,5 +1,5 @@
 using ModelingToolkit, OrdinaryDiffEq, NonlinearSolve, Test
-using StochasticDiffEq, DelayDiffEq, StochasticDelayDiffEq
+using StochasticDiffEq, DelayDiffEq, StochasticDelayDiffEq, JumpProcesses
 using ForwardDiff
 using SymbolicIndexingInterface, SciMLStructures
 using SciMLStructures: Tunable
@@ -1306,3 +1306,29 @@ end
     @test integ[X] ≈ 4.0
     @test integ[Y] ≈ 7.0
 end
+
+@testset "Issue#3297: `generate_initializesystem(::JumpSystem)`" begin
+    @parameters β γ S0
+    @variables S(t)=S0 I(t) R(t)
+    rate₁ = β * S * I
+    affect₁ = [S ~ S - 1, I ~ I + 1]
+    rate₂ = γ * I
+    affect₂ = [I ~ I - 1, R ~ R + 1]
+    j₁ = ConstantRateJump(rate₁, affect₁)
+    j₂ = ConstantRateJump(rate₂, affect₂)
+    j₃ = MassActionJump(2 * β + γ, [R => 1], [S => 1, R => -1])
+    @mtkbuild js = JumpSystem([j₁, j₂, j₃], t, [S, I, R], [β, γ, S0])
+
+    u0s = [I => 1, R => 0]
+    ps = [S0 => 999, β => 0.01, γ => 0.001]
+    dprob = DiscreteProblem(js, u0s, (0.0, 10.0), ps)
+    @test dprob.f.initialization_data !== nothing
+    sol = solve(dprob, FunctionMap())
+    @test sol[S, 1] ≈ 999
+    @test SciMLBase.successful_retcode(sol)
+
+    jprob = JumpProblem(js, dprob)
+    sol = solve(jprob, SSAStepper())
+    @test sol[S, 1] ≈ 999
+    @test SciMLBase.successful_retcode(sol)
+end