ModernUO/Projects/UOContent/Commands/VisibilityList.cs
Kamron Batman cce035f1c3
fix: Removes unnecessary dictionary removal guards (#2565)
## What

`Dictionary<K,V>.Remove` and `HashSet<T>.Remove` do not bump the collection's version, so removing an entry during a `foreach` does not invalidate the enumerator. A number of loops were still paying for a `PooledRefQueue`/`PooledRefList` to collect keys and drain them in a second pass. This drops those guards.

## Why it's safe

Verified against .NET 10.0.10 rather than taken on trust, since the documented guarantee covers only `Dictionary<TKey,TValue>.Remove` while several of these call sites are `HashSet<T>` or enumerate `.Keys`/`.Values`:

| Case | Result |
|---|---|
| `Dictionary` foreach + `Remove` | safe, all entries visited |
| `Dictionary.Keys` / `.Values` foreach + `Remove` | safe, all entries visited |
| `HashSet` foreach + `Remove` | safe, all entries visited |
| `Dictionary` foreach + `Remove` **then `Add`** | throws `InvalidOperationException` |

Reflection on `_version` confirms the mechanism: neither `Dictionary.Remove` nor `HashSet.Remove` touches it. Because `Remove` never bumps the version, the `Keys` and `Values` enumerators are just as safe as the dictionary's own, even though only `Dictionary.Remove` documents the behaviour. No entries were skipped in any case.

The `HashSet` half is confirmed by [stephentoub on dotnet/dotnet-api-docs#8177](https://github.com/dotnet/dotnet-api-docs/issues/8177#issuecomment-1167251052): *"Both HashSet and Dictionary have been improved to support removal during enumeration. The docs may just benefit from updating."* The gap is in the documentation, not the runtime.

`Remove` followed by `Add` in the same enumeration still throws. That is the line this PR does not cross.

## Guards removed

`VisibilityList`, `ChampionTitleSystem`, `Channel`, `BombingRun`, `Ruleset`, `PuzzleChest`, `RaceChangeGump`, `StepCache`, `PlayerMurderSystem`, `VirtueSystem`, `ProjectedItem`, `StaminaSystem`, `AIGroupMovement`, `PromotedGuard`, `AutoDenylist`, `LoginAllowlist`, `AntiMacroSystem`, `DetectHidden`.

Both collection kinds are covered: `Dictionary` (including loops over `.Keys` and `.Values`) and `HashSet` (`ProjectedItem._active`, `PlayerMurderSystem._contextTerms`, `StaminaSystem._resetHash`). In `StaminaSystem.ResetTimer` the `Count == queue.Count → Clear()` branch goes away with the queue — it only existed to avoid paying for N individual removes.

Where the collection supports it, `Contains` + `Remove` and `TryGetValue` + `Remove` also collapse into a single lookup (`if (list.Remove(x))`, `if (m_Pending.Remove(ns, out var state))`).

`Utility.Tidy<K,V>` keeps its two branches: when `K` is serializable the value is not inspected, otherwise the value is. Only the serializable side may be cast, so `Dictionary<Mobile, int>` and `Dictionary<Mobile, string>` stay valid.

## Deliberately unchanged

**`BaseCreature.LoyaltyTimer.OnTick`** keeps its deferred-delete queue. Removing from `World.Mobiles` while enumerating it is safe, but `Mobile.Delete()` is not a `Remove` — it runs `OnDelete`/`OnAfterDelete`, the `OnParentDeleted` cascade over the creature's pack, `DropHolding()`, and region and guild callbacks. Anything in that surface that constructs a `Mobile` is an `Add` into the dictionary being enumerated, which does invalidate it. `BaseHire.PayTimer.OnTick` has the same shape and is likewise untouched.

**Spatial-query buffers** — `GuardedRegion.CallGuards`, `Thunderstorm`, `Exorcism`, `LeverPuzzleController`, `BaseCreature.TeleportPets` — are a different hazard. They buffer the result of a range query because the drain moves or harms mobiles, which mutates sectors mid-enumeration.

**Re-entrant drains.** The `_users` sets in `Firebomb` and the explosion, conflagration and confusion-blast potions look like this pattern but are not: the loop collects, `Clear()`s, and only then runs `Target.Cancel` on each, which can re-enter. `AnimalTrainer` enumerates `pm.Stabled` and drains through `RemoveStabled`, which nulls the `Stabled` field once it empties — safe for an in-flight enumerator, which holds the set reference rather than the field, but subtle enough not to be worth inlining on a cold path.

## Verification

`dotnet build` clean with 0 warnings; 810 Server and 684 UOContent tests pass.
2026-08-08 11:50:01 -07:00

152 lines
5.3 KiB
C#

using System.Collections.Generic;
using ModernUO.CodeGeneratedEvents;
using Server.Mobiles;
using Server.Network;
using Server.Targeting;
namespace Server.Commands
{
public static class VisibilityList
{
public static void Configure()
{
CommandSystem.Register("Vis", AccessLevel.Counselor, Vis_OnCommand);
CommandSystem.Register("VisList", AccessLevel.Counselor, VisList_OnCommand);
CommandSystem.Register("VisClear", AccessLevel.Counselor, VisClear_OnCommand);
}
[OnEvent(nameof(PlayerMobile.PlayerLoginEvent))]
public static void OnLogin(PlayerMobile pm) => pm.VisibilityList.Clear();
[Usage("Vis")]
[Description("Adds or removes a targeted player from your visibility list. Anyone on your visibility list will be able to see you at all times, even when you're hidden.")]
public static void Vis_OnCommand(CommandEventArgs e)
{
if (e.Mobile is PlayerMobile)
{
e.Mobile.Target = new VisTarget();
e.Mobile.SendMessage("Select person to add or remove from your visibility list.");
}
}
[Usage("VisList")]
[Description("Shows the names of everyone in your visibility list.")]
public static void VisList_OnCommand(CommandEventArgs e)
{
if (e.Mobile is PlayerMobile pm)
{
var list = pm.VisibilityList;
if (list.Count > 0)
{
if (list.Count == 1)
{
pm.SendMessage($"You are visible to {list.Count} mobile:");
}
else
{
pm.SendMessage($"You are visible to {list.Count} mobiles:");
}
for (var i = 0; i < list.Count; ++i)
{
pm.SendMessage($"#{i + 1}: {list[i].Name}");
}
}
else
{
pm.SendMessage("Your visibility list is empty.");
}
}
}
[Usage("VisClear")]
[Description("Removes everyone from your visibility list.")]
public static void VisClear_OnCommand(CommandEventArgs e)
{
if (e.Mobile is PlayerMobile pm)
{
var list = new List<Mobile>(pm.VisibilityList);
pm.VisibilityList.Clear();
pm.SendMessage("Your visibility list has been cleared.");
if (list.Count > 0)
{
var removeEntity = stackalloc byte[OutgoingEntityPackets.RemoveEntityLength].InitializePacket();
for (var i = 0; i < list.Count; ++i)
{
var m = list[i];
if (!m.CanSee(pm) && Utility.InUpdateRange(m.Location, pm.Location))
{
OutgoingEntityPackets.CreateRemoveEntity(removeEntity, pm.Serial);
m.NetState?.Send(removeEntity);
}
}
}
}
}
private class VisTarget : Target
{
public VisTarget() : base(-1, false, TargetFlags.None)
{
}
protected override void OnTarget(Mobile from, object targeted)
{
if (from is PlayerMobile pm && targeted is Mobile targ)
{
if (targ.AccessLevel <= pm.AccessLevel)
{
var list = pm.VisibilityList;
if (list.Remove(targ))
{
pm.SendMessage($"{targ.Name} has been removed from your visibility list.");
}
else
{
list.Add(targ);
pm.SendMessage($"{targ.Name} has been added to your visibility list.");
}
if (Utility.InUpdateRange(targ.Location, from.Location))
{
var ns = targ.NetState;
if (ns != null)
{
if (targ.CanSee(pm))
{
ns.SendMobileIncoming(targ, pm);
pm.SendOPLPacketTo(ns);
foreach (var item in pm.Items)
{
item.SendOPLPacketTo(ns);
}
}
else
{
ns.SendRemoveEntity(pm.Serial);
}
}
}
}
else
{
pm.SendMessage("They can already see you!");
}
}
else
{
from.SendMessage("Add only mobiles to your visibility list.");
}
}
}
}
}