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Fix: exiting Play mode from the editor's own Stop button crashed

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Real bug, caught by hand (not by any automated test): clicking Stop in
the Lingua Editor panel threw InvalidOperationException — "A system
structurally changed 'QuadRenderer' without declaring Writes<QuadRenderer>()".

Root cause: GameWorld.Restore rebuilds the world via GameObject.
AddComponent, which SystemAccessScope checks. That's fine when Restore is
called from unconstrained code — every existing WorldSnapshotTests test
calls it directly, outside any system, which is exactly why none of them
caught this. But PlayModeController.ExitPlay is called from inside
EditorPlugin's own Stage.Render system (the button click handler runs as
part of DrawUi), which correctly declares no Reads/Writes at all — it has
no compile-time knowledge of QuadRenderer or any other game's component
types. So the ambient SystemAccessScope was still active when Restore
tried to rebuild them.

SystemAccessScope's own doc comment already said "editor code... [is]
unconstrained by design" — true only when the call happened to originate
outside a system's scope, not actually true in general. Fixed with
SystemAccessScope.Suspend(), which GameWorld.Restore now wraps its entire
rebuild in: Restore is a bulk, whole-world reset regardless of who calls
it, the same category of operation Destroy already is (which never went
through the checked RemoveComponent path to begin with).

New regression test reproduces the exact shape: a system with no declared
access calling Restore, run through the real Schedule — not calling
SystemAccessScope directly, and not calling Restore outside a system
either, which is why this slipped through the first time. Passed
immediately after the fix; would have failed loudly before it.

Full suite: 87 tests.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N1qPfzq8TDCUMFMV3UwV5N
This commit is contained in:
Emil
2026-09-02 17:24:14 +03:00
co-authored by Claude Sonnet 5
parent c6d9ff1a26
commit 88e0afa46b
3 changed files with 56 additions and 0 deletions
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tests/Engine.Kernel.Tests/WorldSnapshotTests.cs
+27
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@@ -1,4 +1,5 @@
using System.Diagnostics;
using Engine.Kernel.Scheduling;
using Engine.Kernel.World;
namespace Engine.Kernel.Tests;
@@ -103,4 +104,30 @@ public class WorldSnapshotTests
stopwatch.ElapsedMilliseconds < 100,
$"Snapshot + Restore of 300 GameObjects took {stopwatch.ElapsedMilliseconds} ms, expected < 100 ms.");
}
// A real bug, caught by hand: entering then exiting Play mode via
// engine.editor's own Stop button threw InvalidOperationException,
// because ExitPlay runs Restore from inside EditorPlugin's Stage.
// Render system — which correctly declares no Reads/Writes at all, it
// has no compile-time knowledge of QuadRenderer or any other game's
// component types — and Restore rebuilds those very types via
// AddComponent. Every other test in this file calls Restore directly,
// outside any system's scope, which is exactly why none of them caught
// this. This one reproduces the real call shape: a system with no
// declared access, calling Restore, run through the real Schedule.
[Fact]
public void Restore_Called_From_A_System_With_No_Declared_Access_Does_Not_Throw()
{
var world = new GameWorld();
var go = world.CreateGameObject("Hero");
go.AddComponent<Health>().Value = 100;
var snapshot = world.Snapshot();
var schedule = new Schedule();
schedule.Add(Stage.Update, (IWorld w) => w.Restore(snapshot)); // no Reads/Writes — like EditorPlugin's DrawUi
var exception = Record.Exception(() => schedule.RunStage(Stage.Update, world));
Assert.Null(exception);
}
}