Merge pull request SciML#2288 from oscardssmith/os/fix-is_constant_cache

fix `is_constant_cache(::DefaultCache)

Author: ChrisRackauckas

src/cache_utils.jl

@@ -1,6 +1,7 @@
-is_constant_cache(cache::OrdinaryDiffEqConstantCache) = true
-is_constant_cache(cache::OrdinaryDiffEqCache) = false
+is_constant_cache(::OrdinaryDiffEqConstantCache) = true
+is_constant_cache(::OrdinaryDiffEqCache) = false
 is_constant_cache(cache::CompositeCache) = is_constant_cache(cache.caches[1])
+is_constant_cache(::DefaultCache{Cache1}) where {Cache1} = Cache1 <: OrdinaryDiffEqConstantCache
 
 function DiffEqBase.unwrap_cache(integrator::ODEIntegrator, is_stiff)
     alg = integrator.alg
@@ -22,6 +23,8 @@ function DiffEqBase.unwrap_cache(integrator::ODEIntegrator, is_stiff)
             return cache.cache5
         elseif current == 6
             return cache.cache6
+        else
+            error("This should not occur (please report a bug)")
         end
     elseif alg.choice_function isa AutoSwitch
         num = is_stiff ? 2 : 1

test/interface/default_solver_tests.jl

@@ -104,3 +104,10 @@ prob_rober_mm = ODEProblem(f, [1.0, 0.0, 1.0], (0.0, 1e5), (0.04, 3e7, 1e4))
 sol = solve(prob_rober_mm)
 @test all(isequal(3), sol.alg_choice)
 @test sol(0.5) isa Vector{Float64} # test dense output
+
+
+# test callback on ConstantCache (https://github.com/SciML/OrdinaryDiffEq.jl/issues/2287)
+using StaticArrays
+cb = ContinuousCallback((u, t, integrator) -> t - 1, (integrator) -> nothing)
+SA_ode_problem = ODEProblem((u, p, t) -> zero(u), SA[0], 2)
+@test solve(SA_ode_problem; callback=cb).retcode == ReturnCode.Success