Merge pull request #3992 from TorkelE/add_missing_event_error

Prevents erroneous creation of discrete events (vector of conditions)

Author: AayushSabharwal

src/systems/callbacks.jl

@@ -438,8 +438,11 @@ function SymbolicDiscreteCallback(
         condition::Union{Symbolic{Bool}, Number, Vector{<:Number}}, affect = nothing;
         initialize = nothing, finalize = nothing,
         reinitializealg = nothing, kwargs...)
-    c = is_timed_condition(condition) ? condition : value(scalarize(condition))
+    # Manual error check (to prevent events like `[X < 5.0] => [X ~ Pre(X) + 10.0]` from being created).
+    (condition isa Vector) && (eltype(condition) <: Num) &&
+        error("Vectors of symbolic conditions are not allowed for `SymbolicDiscreteCallback`.")
 
+    c = is_timed_condition(condition) ? condition : value(scalarize(condition))
     if isnothing(reinitializealg)
         if any(a -> a isa ImperativeAffect,
             [affect, initialize, finalize])

test/symbolic_events.jl

@@ -1440,3 +1440,18 @@ end
     @mtkcompile sys = MWE()
     @test_nowarn ODEProblem(sys, [], (0.0, 1.0))
 end
+
+@testset "Test erroneously created events yields errors" begin
+    @parameters p(t) d
+    @variables X(t)
+    @test_throws "Vectors of symbolic conditions are not allowed" SymbolicDiscreteCallback([X <
+                                                                                            5.0] => [X ~
+                                                                                                     Pre(X) +
+                                                                                                     10.0])
+    @test_throws "Vectors of symbolic conditions are not allowed" SymbolicDiscreteCallback([
+        X < 5.0, X > 10.0] => [X ~ Pre(X) + 10.0])
+    @test_throws "MethodError: no method" SymbolicContinuousCallback((X <
+                                                                      5.0) => [X ~
+                                                                               Pre(X) +
+                                                                               10.0])
+end