CHANGE: Added message to notify the user if a PlayerInputComponent fails to bind a control scheme (ISXB-1020)

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -21,6 +21,7 @@ however, it has to be formatted properly to pass verification tests.
 ### Changed
 - Renamed editor Resources directories to PackageResources to fix package validation warnings.
 - Changed representation of GamepadButton enum values in Inspector to display aliased enum values as a single item to avoid confusion around selection and aliased value display when multiple enum items map to the same numerical value. [ISXB-543](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-543)
+- PlayerInput component now warns if the system cannot find matching control scheme, which can occur if all control schemes already paired (e.g. to other game objects with PlayerInput components) [ISXB-1020](https://issuetracker.unity3d.com/product/unity/issues/guid/ISXB-1020)
 
 ## [1.11.0] - 2024-09-10
 

Packages/com.unity.inputsystem/InputSystem/Plugins/PlayerInput/PlayerInput.cs

@@ -1463,7 +1463,15 @@ private void AssignUserAndDevices()
                     {
                         var controlScheme = InputControlScheme.FindControlSchemeForDevices(availableDevices, m_Actions.controlSchemes);
                         if (controlScheme != null)
+                        {
                             TryToActivateControlScheme(controlScheme.Value);
+                        }
+                        else
+                        {
+                            // The device count check is here to allow the unit tests to pass (and not trigger this error message)
+                            if (InputSystem.devices.Count > 0 && availableDevices.Count == 0)
+                                Debug.LogWarning($"Cannot find matching control scheme for {this.name} (all control schemes are already paired to matching devices)", this);
+                        }
                     }
                 }
             }