test: test code generation for non-standard array indexes

Author: AayushSabharwal

test/code_generation.jl

@@ -1,4 +1,4 @@
-using ModelingToolkit
+using ModelingToolkit, OrdinaryDiffEq
 using ModelingToolkit: t_nounits as t, D_nounits as D
 
 @testset "`generate_custom_function`" begin
@@ -54,3 +54,27 @@ using ModelingToolkit: t_nounits as t, D_nounits as D
     fn5 = generate_custom_function(sys, ifelse(!p4, p1, p2[2]); expression = Val(false))
     @test fn5(u0, p, 1.0) == 1.0
 end
+
+@testset "Non-standard array variables" begin
+    @variables x(t)
+    @parameters p[0:2] (f::Function)(..)
+    @mtkbuild sys = ODESystem(D(x) ~ p[0] * x + p[1] * t + p[2] + f(p), t)
+    prob = ODEProblem(sys, [x => 1.0], (0.0, 1.0), [p => [1.0, 2.0, 3.0], f => sum])
+    @test prob.ps[p] == [1.0, 2.0, 3.0]
+    @test prob.ps[p[0]] == 1.0
+    sol = solve(prob, Tsit5())
+    @test SciMLBase.successful_retcode(sol)
+
+    @testset "Array split across buffers" begin
+        @variables x(t)[0:2]
+        @parameters p[1:2] (f::Function)(..)
+        @named sys = ODESystem(
+            [D(x[0]) ~ p[1] * x[0] + x[2], D(x[1]) ~ p[2] * f(x) + x[2]], t)
+        sys, = structural_simplify(sys, ([x[2]], []))
+        @test is_parameter(sys, x[2])
+        prob = ODEProblem(sys, [x[0] => 1.0, x[1] => 1.0], (0.0, 1.0),
+            [p => ones(2), f => sum, x[2] => 2.0])
+        sol = solve(prob, Tsit5())
+        @test SciMLBase.successful_retcode(sol)
+    end
+end