Improve CompatMgr behaviour for unknown versions

Currently, Impostor will show an "Client is in an invalid state."
message if a player tries to join a match where the host or the joining
player is using a version unknown to Impostor.

This message confused a *lot* of people, so this PR changes the API such
that if the version is not registered, the version itself is put in a
compatibility group and compared, assuming no other game versions are
compatible with it. This works fine in most cases, as Among Us network
versions generally increase over time.

Failure on 2222.2.2 (which is ancient at this point, so likely no longer
used) and future cases where Innersloth messes up (which is unlikely) is
an acceptable consequence to me.

diff --git a/src/Impostor.Server/Net/Manager/CompatibilityManager.cs b/src/Impostor.Server/Net/Manager/CompatibilityManager.cs
index 7ff6aa6a165476a936213ef2db9d4b9478d1d846..f339792c81853467c65ff7ffbce89aed2b0df6b6 100644 (file)
--- a/src/Impostor.Server/Net/Manager/CompatibilityManager.cs
+++ b/src/Impostor.Server/Net/Manager/CompatibilityManager.cs
@@ -63,6 +63,12 @@ internal class CompatibilityManager : ICompatibilityManager
         return null;
     }
 
+    private CompatibilityGroup GetCompatibilityGroupOrDefault(GameVersion clientVersion)
+    {
+        // If the compatibility group is not defined, we assume it is not compatible with anything else than itself
+        return TryGetCompatibilityGroup(clientVersion) ?? new CompatibilityGroup(new[] { clientVersion.Normalize() });
+    }
+
     public VersionCompareResult CanConnectToServer(GameVersion clientVersion)
     {
         if (this.TryGetCompatibilityGroup(clientVersion) != null)
@@ -91,13 +97,8 @@ internal class CompatibilityManager : ICompatibilityManager
             return GameJoinError.None;
         }
 
-        var hostCompatGroup = this.TryGetCompatibilityGroup(hostVersion);
-        var playerCompatGroup = this.TryGetCompatibilityGroup(clientVersion);
-
-        if (hostCompatGroup == null || playerCompatGroup == null)
-        {
-            return GameJoinError.InvalidClient;
-        }
+        var hostCompatGroup = GetCompatibilityGroupOrDefault(hostVersion);
+        var playerCompatGroup = GetCompatibilityGroupOrDefault(clientVersion);
 
         if (hostCompatGroup != playerCompatGroup)
         {

diff --git a/src/Impostor.Tests/CompatibilityManagerTests.cs b/src/Impostor.Tests/CompatibilityManagerTests.cs
index 20cb77623c4a31db628380db57b1bccf890fa885..85ecea623a134861c9173d42568772450ac925ea 100644 (file)
--- a/src/Impostor.Tests/CompatibilityManagerTests.cs
+++ b/src/Impostor.Tests/CompatibilityManagerTests.cs
@@ -48,11 +48,23 @@ public sealed class CompatibilityManagerTests
     public static IEnumerable<object[]> CanJoinGameData =>
         new List<object[]>
         {
+            // Same version -> can join
             new object[] { GameJoinError.None, new GameVersion(1, 0, 0), new GameVersion(1, 0, 0) },
-            new object[] { GameJoinError.InvalidClient, new GameVersion(1, 0, 0), new GameVersion(100, 0, 0) },
+
+            // Compatible versions -> can join
+            new object[] { GameJoinError.None, new GameVersion(2, 0, 0), new GameVersion(2, 1, 0) },
+
+            // Different incompatible versions -> show correct error
             new object[] { GameJoinError.ClientOutdated, new GameVersion(2, 0, 0), new GameVersion(1, 0, 0) },
             new object[] { GameJoinError.ClientTooNew, new GameVersion(1, 0, 0), new GameVersion(2, 0, 0) },
-            new object[] { GameJoinError.None, new GameVersion(2, 0, 0), new GameVersion(2, 1, 0) },
+
+            // Versions unknown to Impostor -> also show correct errors
+            new object[] { GameJoinError.ClientTooNew, new GameVersion(0, 0, 1), new GameVersion(1, 0, 0) },
+            new object[] { GameJoinError.ClientOutdated, new GameVersion(1, 0, 0), new GameVersion(0, 0, 1) },
+            new object[] { GameJoinError.ClientTooNew, new GameVersion(1, 0, 0), new GameVersion(100, 0, 0) },
+            new object[] { GameJoinError.ClientOutdated, new GameVersion(100, 0, 0), new GameVersion(1, 0, 0) },
+            new object[] { GameJoinError.ClientTooNew, new GameVersion(0, 0, 1), new GameVersion(100, 0, 0) },
+
         };
 
     [Theory]