FIX: [Port] [UUM-137448] Fixed layout merge for controls declared for several variants (#2505)

Author: josepmariapujol-unity

Assets/Tests/InputSystem/CoreTests_Layouts.cs

@@ -2624,6 +2624,50 @@ public void Layouts_CanMatchControlPath()
         Assert.That(layout.m_Controls.Any(x => InputControlPath.MatchControlComponent(ref parsedUsagesPath, ref x)), Is.True);
     }
 
+    [Test]
+    [Category("Layouts")]
+    public void Layouts_ControlDeclaredForSeveralVariants_MergesUnderEachOfThem()
+    {
+        const string jsonBase = @"
+            {
+                ""name"" : ""VariantBaseCombined"",
+                ""extend"" : ""Gamepad"",
+                ""controls"" : [
+                    { ""name"" : ""custom"", ""layout"" : ""Axis"", ""variants"" : ""lefty;righty"", ""offset"" : 32 }
+                ]
+            }
+        ";
+        const string jsonDerived = @"
+            {
+                ""name"" : ""VariantDerivedFromCombined"",
+                ""extend"" : ""VariantBaseCombined"",
+                ""controls"" : [
+                    { ""name"" : ""custom"", ""variants"" : ""lefty"", ""format"" : ""FLT"" },
+                    { ""name"" : ""custom"", ""variants"" : ""righty"", ""format"" : ""FLT"" }
+                ]
+            }
+        ";
+
+        InputSystem.RegisterLayout(jsonBase);
+        InputSystem.RegisterLayout(jsonDerived);
+
+        var layout = InputSystem.LoadLayout("VariantDerivedFromCombined");
+
+        // Both variants named in the base must merge with the derived controls and inherit
+        // the base's settings, not just the first one.
+        var lefty = layout.controls.Single(x => x.name.ToString() == "custom" &&
+            string.Equals(x.variants.ToString(), "lefty", StringComparison.OrdinalIgnoreCase));
+        var righty = layout.controls.Single(x => x.name.ToString() == "custom" &&
+            string.Equals(x.variants.ToString(), "righty", StringComparison.OrdinalIgnoreCase));
+
+        Assert.That(lefty.layout.ToString(), Is.EqualTo("Axis"));
+        Assert.That(righty.layout.ToString(), Is.EqualTo("Axis"));
+        Assert.That(lefty.offset, Is.EqualTo(32));
+        Assert.That(righty.offset, Is.EqualTo(32));
+        Assert.That(lefty.format, Is.EqualTo(new FourCC("FLT")));
+        Assert.That(righty.format, Is.EqualTo(new FourCC("FLT")));
+    }
+
     [Test]
     [Category("Layouts")]
     [Ignore("TODO")]

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed touch input from Unity Remote 5 being ignored in Unity 6000.5 and newer. [UUM-155327](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-155327)
 - Fixed actions enabled during startup, for example in an Entities system's `OnCreate`, being disabled when entering Play Mode with domain reload disabled and in Player builds. [UUM-151403](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-151403)
 - Fixed the Player Input component Inspector not showing the action map events after the Behavior is set to Invoke Unity Events, until the GameObject was selected again. [UUM-150956](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-150956)
+- Fixed a control declared for several variants at once (for example `"variants" : "A;B"`) only merging with derived layouts under its first variant; derived overrides for the other variants lost the base control's layout, offset, format and usages. [UUM-160829](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-160829)
 
 ## [1.20.1] - 2026-10-05
 

Packages/com.unity.inputsystem/InputSystem/Runtime/Controls/InputControlLayout.cs

@@ -1485,8 +1485,7 @@ private static Dictionary<string, ControlItem> CreateLookupTableForControls(
                         foreach (var name in itemVariantArray)
                         {
                             variants?.Add(name);
-                            key = $"{key}@{name}";
-                            table[key] = controlItems[i];
+                            table[$"{key}@{name}"] = controlItems[i];
                         }
 
                         continue;