Handle dummy derivative u0's and throw custom incomplete init error

Author: ChrisRackauckas

src/systems/diffeqs/abstractodesystem.jl

@@ -1540,6 +1540,21 @@ function InitializationProblem{false}(sys::AbstractODESystem, args...; kwargs...
     InitializationProblem{false, SciMLBase.FullSpecialize}(sys, args...; kwargs...)
 end
 
+const INCOMPLETE_INITIALIZATION_MESSAGE = """
+                                Initialization incomplete. Not all of the state variables of the
+                                DAE system can be determined by the initialization. Missing
+                                variables:
+                                """
+
+struct IncompleteInitializationError <: Exception 
+    uninit
+end
+
+function Base.showerror(io::IO, e::IncompleteInitializationError)
+    println(io, INCOMPLETE_INITIALIZATION_MESSAGE)
+    println(io, e.uninit)
+end
+
 function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
         t::Number, u0map = [],
         parammap = DiffEqBase.NullParameters();
@@ -1560,6 +1575,11 @@ function InitializationProblem{iip, specialize}(sys::AbstractODESystem,
             generate_initializesystem(sys; u0map); fully_determined = false)
     end
 
+    uninit = setdiff(unknowns(sys),[unknowns(isys); getfield.(observed(isys),:lhs)])
+    if !isempty(uninit)
+        throw(IncompleteInitializationError(uninit))
+    end
+
     neqs = length(equations(isys))
     nunknown = length(unknowns(isys))
 

src/systems/nonlinear/initializesystem.jl

@@ -17,21 +17,23 @@ function generate_initializesystem(sys::ODESystem;
     # Start the equations list with algebraic equations
     eqs_ics = eqs[idxs_alge]
     u0 = Vector{Pair}(undef, 0)
-    defs = merge(defaults(sys), todict(u0map))
 
     full_states = [sts; getfield.((observed(sys)), :lhs)]
     set_full_states = Set(full_states)
     guesses = todict(guesses)
     schedule = getfield(sys, :schedule)
-
-    dd_guess = if schedule !== nothing
+    
+    if schedule !== nothing
         guessmap = [x[2] => get(guesses, x[1], default_dd_value)
                     for x in schedule.dummy_sub]
-        Dict(filter(x -> !isnothing(x[1]), guessmap))
+        dd_guess = Dict(filter(x -> !isnothing(x[1]), guessmap))
+        filtered_u0 = todict([get(schedule.dummy_sub, x[1], x[1]) => x[2] for x in u0map])
     else
-        Dict()
+        dd_guess = Dict()
+        filtered_u0 = u0map
     end
 
+    defs = merge(defaults(sys), filtered_u0)
     guesses = merge(get_guesses(sys), todict(guesses), dd_guess)
 
     for st in full_states

test/initializationsystem.jl

@@ -331,7 +331,7 @@ p = [σ => 28.0,
     β => 8 / 3]
 
 tspan = (0.0, 100.0)
-@test_throws ArgumentError prob=ODEProblem(sys, u0, tspan, p, jac = true)
+@test_throws ModelingToolkit.IncompleteInitializationError prob=ODEProblem(sys, u0, tspan, p, jac = true)
 
 # DAE Initialization on ODE with nonlinear system for initial conditions
 # https://github.com/SciML/ModelingToolkit.jl/issues/2508