fixup! feat: allow initialization of null integrators

Author: AayushSabharwal

src/initialize_dae.jl

@@ -140,20 +140,7 @@ end
 function _initialize_dae!(integrator, prob::Union{ODEProblem, DAEProblem},
         alg::OverrideInit, isinplace::Union{Val{true}, Val{false}})
     initializeprob = prob.f.initializeprob
-    if initializeprob.f.sys !== nothing && prob.f.sys !== nothing
-        if initializeprob.u0 === nothing || isempty(initializeprob.u0)
-            initu0 = Float64[]
-        else
-            initu0vars = variable_symbols(initializeprob)
-            initu0order = variable_index.((initializeprob,), initu0vars)
-            # Variable symbols are not guaranteed to be in order
-            invpermute!(initu0vars, initu0order)
-            initu0 = getu(prob.f.initializeprob, initu0vars)(prob)
-        end
-        initp = remake_buffer(initializeprob, parameter_values(initializeprob),
-            Dict(sym => getu(prob, sym)(prob) for sym in parameter_symbols(initializeprob)))
-        initializeprob = remake(initializeprob; u0 = initu0, p = initp)
-    end
+    prob.f.initializeprob_init!(initializeprob, integrator)
     # If it doesn't have autodiff, assume it comes from symbolic system like ModelingToolkit
     # Since then it's the case of not a DAE but has initializeprob
     # In which case, it should be differentiable
@@ -168,19 +155,9 @@ function _initialize_dae!(integrator, prob::Union{ODEProblem, DAEProblem},
     alg = default_nlsolve(alg.nlsolve, isinplace, initializeprob.u0, initializeprob, isAD)
     nlsol = solve(initializeprob, alg)
     if isinplace === Val{true}()
-        if prob.u0 !== nothing && !isempty(prob.u0)
-            integrator.u .= prob.f.initializeprobmap(nlsol)
-        end
-        if SciMLBase.has_initializeprob_updatep(prob.f)
-            prob.f.initializeprob_updatep!(integrator.p, nlsol)
-        end
+        prob.f.initializeprob_update!(integrator, nlsol)
     elseif isinplace === Val{false}()
-        if prob.u0 !== nothing && !isempty(prob.u0)
-            integrator.u .= prob.f.initializeprobmap(nlsol)
-        end
-        if SciMLBase.has_initializeprob_updatep(prob.f)
-            prob.f.initializeprob_updatep!(integrator.p, nlsol)
-        end
+        prob.f.initializeprob_update!(integrator, nlsol)
     else
         error("Unreachable reached. Report this error.")
     end