feat: more robust inputs/outputs handling

src/inputoutput.jl

@@ -5,7 +5,7 @@ using Symbolics: get_variables
 Return all variables that mare marked as inputs. See also [`unbound_inputs`](@ref)
 See also [`bound_inputs`](@ref), [`unbound_inputs`](@ref)
 """
-inputs(sys) = [filter(isinput, unknowns(sys)); filter(isinput, parameters(sys))]
+inputs(sys) = collect(get_inputs(sys))
 
 """
     outputs(sys)
@@ -14,13 +14,7 @@ Return all variables that mare marked as outputs. See also [`unbound_outputs`](@
 See also [`bound_outputs`](@ref), [`unbound_outputs`](@ref)
 """
 function outputs(sys)
-    o = observed(sys)
-    rhss = [eq.rhs for eq in o]
-    lhss = [eq.lhs for eq in o]
-    unique([filter(isoutput, unknowns(sys))
-            filter(isoutput, parameters(sys))
-            filter(x -> iscall(x) && isoutput(x), rhss) # observed can return equations with complicated expressions, we are only looking for single Terms
-            filter(x -> iscall(x) && isoutput(x), lhss)])
+    return collect(get_outputs(sys))
 end
 
 """
@@ -316,6 +310,8 @@ function inputs_to_parameters!(state::TransformationState, inputsyms)
     ps = parameters(sys)
 
     @set! sys.ps = [ps; new_parameters]
+    @set! sys.inputs = Set{BasicSymbolic}(filter(isinput, fullvars))
+    @set! sys.outputs = Set{BasicSymbolic}(filter(isoutput, fullvars))
     @set! state.sys = sys
     @set! state.fullvars = Vector{BasicSymbolic}(new_fullvars)
     @set! state.structure = structure

src/systems/abstractsystem.jl

@@ -767,6 +767,8 @@ const SYS_PROPS = [:eqs
                    :parent
                    :is_dde
                    :tstops
+                   :inputs
+                   :outputs
                    :index_cache
                    :isscheduled
                    :costs

src/systems/system.jl

@@ -190,6 +190,16 @@ struct System <: AbstractSystem
     """
     tstops::Vector{Any}
     """
+    $INTERNAL_FIELD_WARNING
+    The list of input variables of the system.
+    """
+    inputs::Set{BasicSymbolic}
+    """
+    $INTERNAL_FIELD_WARNING
+    The list of output variables of the system.
+    """
+    outputs::Set{BasicSymbolic}
+    """
     The `TearingState` of the system post-simplification with `mtkcompile`.
     """
     tearing_state::Any
@@ -255,8 +265,9 @@ struct System <: AbstractSystem
             brownians, iv, observed, parameter_dependencies, var_to_name, name, description,
             defaults, guesses, systems, initialization_eqs, continuous_events, discrete_events,
             connector_type, assertions = Dict{BasicSymbolic, String}(),
-            metadata = MetadataT(), gui_metadata = nothing,
-            is_dde = false, tstops = [], tearing_state = nothing, namespacing = true,
+            metadata = MetadataT(), gui_metadata = nothing, is_dde = false, tstops = [],
+            inputs = Set{BasicSymbolic}(), outputs = Set{BasicSymbolic}(),
+            tearing_state = nothing, namespacing = true,
             complete = false, index_cache = nothing, ignored_connections = nothing,
             preface = nothing, parent = nothing, initializesystem = nothing,
             is_initializesystem = false, is_discrete = false, isscheduled = false,
@@ -296,7 +307,8 @@ struct System <: AbstractSystem
             observed, parameter_dependencies, var_to_name, name, description, defaults,
             guesses, systems, initialization_eqs, continuous_events, discrete_events,
             connector_type, assertions, metadata, gui_metadata, is_dde,
-            tstops, tearing_state, namespacing, complete, index_cache, ignored_connections,
+            tstops, inputs, outputs, tearing_state, namespacing,
+            complete, index_cache, ignored_connections,
             preface, parent, initializesystem, is_initializesystem, is_discrete,
             isscheduled, schedule)
     end
@@ -367,15 +379,27 @@ function System(eqs::Vector{Equation}, iv, dvs, ps, brownians = [];
 
     defaults = anydict(defaults)
     guesses = anydict(guesses)
+    inputs = Set{BasicSymbolic}()
+    outputs = Set{BasicSymbolic}()
     var_to_name = anydict()
 
     let defaults = discover_from_metadata ? defaults : Dict(),
-        guesses = discover_from_metadata ? guesses : Dict()
+        guesses = discover_from_metadata ? guesses : Dict(),
+        inputs = discover_from_metadata ? inputs : Set(),
+        outputs = discover_from_metadata ? outputs : Set()
 
         process_variables!(var_to_name, defaults, guesses, dvs)
         process_variables!(var_to_name, defaults, guesses, ps)
         process_variables!(var_to_name, defaults, guesses, [eq.lhs for eq in observed])
         process_variables!(var_to_name, defaults, guesses, [eq.rhs for eq in observed])
+
+        for var in dvs
+            if isinput(var)
+                push!(inputs, var)
+            elseif isoutput(var)
+                push!(outputs, var)
+            end
+        end
     end
     filter!(!(isnothing ∘ last), defaults)
     filter!(!(isnothing ∘ last), guesses)
@@ -416,7 +440,8 @@ function System(eqs::Vector{Equation}, iv, dvs, ps, brownians = [];
         costs, consolidate, dvs, ps, brownians, iv, observed, Equation[],
         var_to_name, name, description, defaults, guesses, systems, initialization_eqs,
         continuous_events, discrete_events, connector_type, assertions, metadata, gui_metadata, is_dde,
-        tstops, tearing_state, true, false, nothing, ignored_connections, preface, parent,
+        tstops, inputs, outputs, tearing_state, true, false,
+        nothing, ignored_connections, preface, parent,
         initializesystem, is_initializesystem, is_discrete; checks)
 end
 
@@ -1141,6 +1166,8 @@ function Base.isapprox(sysa::System, sysb::System)
            isequal(get_metadata(sysa), get_metadata(sysb)) &&
            isequal(get_is_dde(sysa), get_is_dde(sysb)) &&
            issetequal(get_tstops(sysa), get_tstops(sysb)) &&
+           issetequal(get_inputs(sysa), get_inputs(sysb)) &&
+           issetequal(get_outputs(sysa), get_outputs(sysb)) &&
            safe_issetequal(get_ignored_connections(sysa), get_ignored_connections(sysb)) &&
            isequal(get_is_initializesystem(sysa), get_is_initializesystem(sysb)) &&
            isequal(get_is_discrete(sysa), get_is_discrete(sysb)) &&

test/input_output_handling.jl

@@ -464,3 +464,20 @@ end
     x = [1.0]
     @test_nowarn f[1](x, u, p, 0.0)
 end
+
+@testset "Observed inputs and outputs" begin
+    @variables x(t) y(t) [input = true] z(t) [output = true]
+    eqs = [D(x) ~ x + y + z
+           y ~ z]
+    @named sys = System(eqs, t)
+    @test issetequal(ModelingToolkit.inputs(sys), [y])
+    @test issetequal(ModelingToolkit.outputs(sys), [z])
+
+    ss1 = mtkcompile(sys, inputs = [y], outputs = [z])
+    @test issetequal(ModelingToolkit.inputs(ss1), [y])
+    @test issetequal(ModelingToolkit.outputs(ss1), [z])
+
+    ss2 = mtkcompile(sys, inputs = [z], outputs = [y])
+    @test issetequal(ModelingToolkit.inputs(ss2), [z])
+    @test issetequal(ModelingToolkit.outputs(ss2), [y])
+end