Spy disguise weapons not updating when swapping disguises to spy from another class [TF2items Manager]

[kingofings]

If a spy is on the other team and uses a revolver with modified attributes he will not be able to change the disguise weapon to that revolver. This also causes the weapons not to update. E.g. When disguised as a demoman and swapping disguise to spy the Grenade launcher will still render on the spy. If all of the spies weapons have modified attributes he is not able to change disguise weapons at all.

If your first disguise is a spy with the above conditions you will not be able to swap to any of the modified disguise weapons, and will only have a sapper. On some cases the disguise will fallback to a random players weapons like a rocket launcher and show as a T Pose.

This only affects spy disguises!

Steps to reproduce the behavior of the first issue:

1. Modify any attributes of a spy weapon and let an enemy spy equip it (eg revolver)
2. Disguise as any class except spy
3. Swap disguise to spy

Steps to reproduce the behavior of the second issue:

1. Modify any attributes of a spy weapon and equip it (eg revolver)
2. Disguise as spy with an enemy spy with modified attributes

Expected behavior
Swap disguise weapons as normal, Don't render previous disguise weapons

Screenshots

Environment

• Sourcemod 1.10.0.6502
• Metamod 1.11.0-dev+1144
• Ubuntu 20.04.2 LTS

[BringBackQuickPlay]

Here's the solution. The comments contains my observations on the problem.
EDIT: This breaks the dropped weapon functionality of TF2, working on a improvement to this fix to take that into account.

public Action TF2Items_OnGiveNamedItem(int client, char[] class, int index, Handle& itemTarget) {
Handle itemNew;
// TF2Items_OnGiveNamedItem defaults to setting bForce to false for CTFPlayer::GiveNamedItem in tf_player.cpp when using it to change weapon attributes.
// this causes issues when a disguised spy (say, using a soldier disguise) disguises as enemy spy, leading to T-posing since the target enemy spies
// weapons are not properly copied into the m_hDisguiseWeaponList list since the disguised spy already "owns" the weapon types.
// When the game later uses DetermineDisguiseWeapon, it fails to do so since the list does not have the appropiate weapon 
// for your current selection (ex: Ambassador) and falls back to using last disguise weapon, which in this example would be whatever you had on your soldier disguise.
// It also traverses the m_hDisguiseWeaponList from first to last (primary, secondary and so on). That's why touching only knife with changes
// does not lead to t-pose but cannot switch to knife, but touching revolvers does.
// See here: https://github.com/ValveSoftware/source-sdk-2013/blob/2d3a6efb50bba856a44e73d4f0098ed4a726699c/src/game/server/tf/tf_player.cpp#L22629
// and here: https://github.com/ValveSoftware/source-sdk-2013/blob/2d3a6efb50bba856a44e73d4f0098ed4a726699c/src/game/server/tf/tf_player.cpp#L5540
// When it runs CreateDisguiseWeaponList, notice how bForce is set to true. I.e GiveNamedItem( pWeapon->GetClassname(), iSubType, pItem, true )
// We need to make sure that when GiveNamedItem is about to give a spy weapon to a disguised spys m_hDisguiseWeaponList, we set bForce to true ourself.
// While we cannot directly check if GiveNamedItem is being called in the context of filling out the m_hDisguiseWeaponList, we can be pretty
// sure that it is being called in that Context by doing the following:
// First check: is GiveNamedItem trying to give a spy weapon to client?
bool isGivingSpyWeapon = (
	(index == 61 || index == 1006) || (index == 460) || // (Ambassador) OR (Enforcer) OR
	(index == 810 || index == 831) || (index == 225 || index == 574) || (index == 649) // (Red-Tape Recorder) OR (Your Eternal Reward) OR (Spy-Cicle)
);

// Second check: Is GiveNamedItem trying to give to a: Living (i.e not DEAD) client who's Spy, that is already disguised AND isGivingSpyWeapon was true.
bool needForce =
IsPlayerAlive(client) &&
TF2_GetPlayerClass(client) == TFClass_Spy &&
TF2_IsPlayerInCondition(client, TFCond_Disguised) &&
isGivingSpyWeapon;

// IF needForce is true, we need add the FORCE_GENERATION flag to TF2Items_CreateItem so that TF2Items sets bForce to True for CTFPlayer::GiveNamedItem
// IF needForce is false, it's a non-spy class being given a item with GiveNamedItem, do not give FORCE_GENERATION flag or server will eventually crash from to many networked entities.
// ClearDisguiseWeaponList is run in OnRemoveDisguised and in CTFPlayerShared::ConditionGameRulesThink whenever player is not disguised. With our needForce check, we also ensure
// we only give bForce to items that would have ended up in m_hDisguiseWeaponList so we know this won't grow out of control.
itemNew = TF2Items_CreateItem( needForce ? (OVERRIDE_ATTRIBUTES | PRESERVE_ATTRIBUTES | FORCE_GENERATION)
: (OVERRIDE_ATTRIBUTES | PRESERVE_ATTRIBUTES));

// The rest of your code below

[BringBackQuickPlay]

If you are touching the regular revolver then don't forget to add it's DefIndex as seen in items_game.txt,
to the IsGivingSpyWeapon bool.