feat: enable structural_simplify(::SDESystem)

Author: AayushSabharwal

src/systems/systems.jl

@@ -72,6 +72,10 @@ function __structural_simplify(sys::JumpSystem, args...; kwargs...)
     return sys
 end
 
+function __structural_simplify(sys::SDESystem, args...; kwargs...)
+    return __structural_simplify(ODESystem(sys), args...; kwargs...)
+end
+
 function __structural_simplify(sys::AbstractSystem, io = nothing; simplify = false,
         kwargs...)
     sys = expand_connections(sys)

test/sdesystem.jl

@@ -858,3 +858,13 @@ end
         end
     end
 end
+
+@testset "`structural_simplify(::SDESystem)`" begin
+    @variables x(t) y(t)
+    @mtkbuild sys = SDESystem(
+        [D(x) ~ x, y ~ 2x], [x, 0], t, [x, y], []; is_scalar_noise = true)
+    @test sys isa SDESystem
+    @test length(equations(sys)) == 1
+    @test length(ModelingToolkit.get_noiseeqs(sys)) == 1
+    @test length(observed(sys)) == 1
+end