add error for discrete parameter update, do not add observed to algebraic equations

Author: vyudu

src/systems/abstractsystem.jl

@@ -648,12 +648,12 @@ function complete(
         if has_continuous_events(sys) && is_time_dependent(sys)
             @set! sys.continuous_events = complete.(
                 get_continuous_events(sys); iv = get_iv(sys),
-                alg_eqs = [alg_equations(sys); observed(sys)])
+                alg_eqs = alg_equations(sys))
         end
         if has_discrete_events(sys) && is_time_dependent(sys)
             @set! sys.discrete_events = complete.(
                 get_discrete_events(sys); iv = get_iv(sys),
-                alg_eqs = [alg_equations(sys); observed(sys)])
+                alg_eqs = alg_equations(sys))
         end
     end
     if split && has_index_cache(sys)

src/systems/callbacks.jl

@@ -31,6 +31,8 @@ function Symbolics.fast_substitute(aff::SymbolicAffect, rules)
         map(substituter, aff.discrete_parameters))
 end
 
+all_equations(a::SymbolicAffect) = [a.affect; a.alg_eqs]
+
 struct AffectSystem
     """The internal implicit discrete system whose equations are solved to obtain values after the affect."""
     system::AbstractSystem
@@ -84,6 +86,9 @@ function AffectSystem(affect::Vector{Equation}; discrete_parameters = Any[],
              symbolic_type(eq.lhs) === NotSymbolic())
             @warn "Affect equation $eq has no `Pre` operator. As such it will be interpreted as an algebraic equation to be satisfied after the callback. If you intended to use the value of a variable x before the affect, use Pre(x). Errors may be thrown if there is no `Pre` and the algebraic equation is unsatisfiable, such as X ~ X + 1."
         end
+        if ModelingToolkit.isparameter(eq.lhs) && (eq.lhs ∉ OrderedSet(discrete_parameters))
+            error("Detected explicit update to parameter $(eq.lhs), but it has not been passed in as a `discrete_parameters` to the callback constructor, for example: \n\n(SymbolicDiscreteCallback(cond => aff, discrete_parameters = [$(eq.lhs)])\n\nAs a result, the parameter update will fail.")
+        end
         collect_vars!(dvs, params, eq, iv; op = Pre)
         empty!(_varsbuf)
         vars!(_varsbuf, eq; op = Pre)