Fix remake of ForwardDiffSensitivity

Fixes #1137

Author: ChrisRackauckas

src/forward_sensitivity.jl

@@ -675,8 +675,14 @@ function SciMLBase.remake(
         {uType, tType, isinplace, P, F, K}
     _p = p === nothing ? parameter_values(prob) : p
     _f = f === nothing ? prob.f.f : f
-    _u0 = u0 === nothing ? state_values(prob, 1:(prob.f.numindvar)) :
-          u0[1:(prob.f.numindvar)]
+
+    if typeof(_f) <: ODEForwardSensitivityFunction
+        _u0 = u0 === nothing ? state_values(prob, 1:(_f.numindvar)) :
+            u0[1:(_f.numindvar)]
+    else
+        _u0 = u0 === nothing ? state_values(prob) : u0
+    end
+    
     _tspan = tspan === nothing ? prob.tspan : tspan
     ODEForwardSensitivityProblem(_f, _u0,
         _tspan, _p; sensealg = prob.problem_type.sensealg,

test/forward.jl

@@ -271,3 +271,15 @@ f = prob.f
 @assert f isa ODEForwardSensitivityFunction
 @test hasproperty(f, :observed)
 @test f.observed == SciMLBase.DEFAULT_OBSERVED
+
+# `remake`: https://github.com/SciML/SciMLSensitivity.jl/issues/1137
+
+function f(du, u, p, t)
+    du[1] = dx = p[1] * u[1] - p[2] * u[1] * u[2]
+    du[2] = dy = -p[3] * u[2] + u[1] * u[2]
+end
+
+p = [1.5, 1.0, 3.0]
+ts = (0, 10)
+prob = ODEForwardSensitivityProblem(f, [1.0; 1.0], ts, p, sensealg=ForwardDiffSensitivity())
+sol = solve(prob, Tsit5())