Merge pull request #1236 from SciML/myb/extend

More robust system nesting

Author: YingboMa

src/systems/abstractsystem.jl

@@ -948,7 +948,7 @@ by default.
 function extend(sys::AbstractSystem, basesys::AbstractSystem; name::Symbol=nameof(sys))
     T = SciMLBase.parameterless_type(basesys)
     ivs = independent_variables(basesys)
-    if !(typeof(sys) <: T)
+    if !(sys isa T)
         if length(ivs) == 0
             sys = convert_system(T, sys)
         elseif length(ivs) == 1
@@ -958,11 +958,11 @@ function extend(sys::AbstractSystem, basesys::AbstractSystem; name::Symbol=nameo
         end
     end
 
-    eqs = union(equations(basesys), equations(sys))
-    sts = union(states(basesys), states(sys))
-    ps = union(parameters(basesys), parameters(sys))
-    obs = union(observed(basesys), observed(sys))
-    defs = merge(defaults(basesys), defaults(sys)) # prefer `sys`
+    eqs = union(get_eqs(basesys), get_eqs(sys))
+    sts = union(get_states(basesys), get_states(sys))
+    ps = union(get_ps(basesys), get_ps(sys))
+    obs = union(get_observed(basesys), get_observed(sys))
+    defs = merge(get_defaults(basesys), get_defaults(sys)) # prefer `sys`
     syss = union(get_systems(basesys), get_systems(sys))
 
     if length(ivs) == 0
@@ -984,7 +984,7 @@ function compose(sys::AbstractSystem, systems::AbstractArray{<:AbstractSystem};
     nsys = length(systems)
     nsys >= 1 || throw(ArgumentError("There must be at least 1 subsystem. Got $nsys subsystems."))
     @set! sys.name = name
-    @set! sys.systems = systems
+    @set! sys.systems = [get_systems(sys); systems]
     return sys
 end
 compose(syss::AbstractSystem...; name=nameof(first(syss))) = compose(first(syss), collect(syss[2:end]); name=name)

src/systems/diffeqs/odesystem.jl

@@ -187,6 +187,7 @@ end
 
 # NOTE: equality does not check cached Jacobian
 function Base.:(==)(sys1::ODESystem, sys2::ODESystem)
+    sys1 === sys2 && return true
     iv1 = get_iv(sys1)
     iv2 = get_iv(sys2)
     isequal(iv1, iv2) &&

test/components.jl

@@ -47,3 +47,11 @@ sol = solve(prob, Rodas4())
 
 prob = ODAEProblem(sys, u0, (0, 10.0))
 sol = solve(prob, Tsit5())
+
+@variables t x1(t) x2(t) x3(t) x4(t)
+D = Differential(t)
+@named sys1_inner = ODESystem([D(x1) ~ x1], t)
+@named sys1_partial = compose(ODESystem([D(x2) ~ x2], t; name=:foo), sys1_inner)
+@named sys1 = extend(ODESystem([D(x3) ~ x3], t; name=:foo), sys1_partial)
+@named sys2 = compose(ODESystem([D(x4) ~ x4], t; name=:foo), sys1)
+@test_nowarn sys2.sys1.sys1_inner.x1 # test the correct nesting