Add a hook to govern the application of effects in a similar manner to CanAbilityHitUnit

[ReshiMael]

Goal: Provide widely applicable and easy to use tool to govern whether or not effects are allowed to be applied to a unit, providing a similar result to CanAbilityHitUnit, which directly governs what abilities are allowed to apply to a unit.

Something in the vein of: EffectShouldRedirect() as declared in X2Effect_Persistent.
Maybe something along the lines of adding the code as follows to ApplyEffect in X2Effect, and adding a function bool to X2Effect that enables this functionality:

simulated final function name X2Effect::ApplyEffect(/**/)
{
if (TargetStateObject != none)
{
if (TargetStateObject.IsImmuneToEffect(self, SourceStateObject, AbilityStateObject))
{
return 'AA_UnitIsImmune';
}
}
}

And in XGS_Unit
function bool IsImmuneToEffect(X2Effect Effect, XComGameState_Unit SourceUnit, XComGameState_Ability AbilityState)
{
local XComGameStateHistory History;
local XComGameState_Effect EffectState;

History = `XCOMHISTORY;

foreach AffectedByEffects(EffectRef)
{
    EffectState = XComGameState_Effect(History.GetGameStateForObjectID(EffectRef.ObjectID));
    if (EffectState.GetX2Effect().ProvidesImmunityToEffect(Effect, EffectState, SourceUnit, self, AbilityState))
    {
        return true;
    }
}

return false;

}

and in X2Effect_Persistent
function bool ProvidesImmunityToEffect(X2Effect Effect, XComGameState_Effect EffectState, XComGameState_Unit SourceUnit, XComGameState_Unit TargetUnit, XComGameState_Ability AbilityState) { return false; }

Thanks for the help with figuring out a better implementation for this, Merist o7

[M3r1st]

I'd suggest less loaded definitions:

EDIT: ApplyEffectParameters can be replaced with states or references to make the functions usable in other functions

simulated final function name X2Effect::ApplyEffect(/**/)
{
    //

    if (TargetStateObject != none)
    {
        if (TargetStateObject.IsImmuneToEffect(ApplyEffectParameters))
        {
            return 'AA_UnitIsImmune';
        }
    }

    //
}

function bool XComGameState_Unit::IsImmuneToEffect(const out EffectAppliedData ApplyEffectParameters)
{
    local XComGameStateHistory History;
	local XComGameState_Effect EffectState;

    History = `XCOMHISTORY;

    foreach AffectedByEffects(EffectRef)
    {
        EffectState = XComGameState_Effect(History.GetGameStateForObjectID(EffectRef.ObjectID));
        if (EffectState.GetX2Effect().ProvidesImmunityToEffect(EffectState, ApplyEffectParameters))
        {
            return true;
        }
    }

    return false;
}

function bool X2Effect_Persistent::ProvidesImmunityToEffect(XComGameState_Effect EffectState, const out EffectAppliedData ApplyEffectParameters) { return false; }