FIX: JSON read changing empty binding path to null (case 1231968, #1237).

Author: Rene Damm

Assets/Tests/InputSystem/CoreTests_Actions.cs

@@ -2679,12 +2679,17 @@ public void Actions_CanConvertActionMapToAndFromJson()
         //Give action maps stable internal names (just like actions)
         var map = new InputActionMap("test");
 
-        map.AddAction(name: "action1", expectedControlLayout: "Button", binding: "/gamepad/leftStick")
+        var action1 = map.AddAction(name: "action1", expectedControlLayout: "Button", binding: "/gamepad/leftStick");
+        action1
             .AddBinding("/gamepad/rightStick")
             .WithGroup("group")
             .WithProcessor("deadzone");
         map.AddAction(name: "action2", binding: "/gamepad/buttonSouth", interactions: "tap,slowTap(duration=0.1)");
 
+        // Add binding with an empty path and make sure we persist that correctly.
+        // https://fogbugz.unity3d.com/f/cases/1231968/
+        action1.AddBinding("");
+
         var json = map.ToJson();
         var maps = InputActionMap.FromJson(json);
 
@@ -2698,8 +2703,12 @@ public void Actions_CanConvertActionMapToAndFromJson()
         Assert.That(maps[0].actions[1].id, Is.EqualTo(map["action2"].id));
         Assert.That(maps[0].actions[0].expectedControlType, Is.EqualTo("Button"));
         Assert.That(maps[0].actions[1].expectedControlType, Is.Null);
-        Assert.That(maps[0].actions[0].bindings, Has.Count.EqualTo(2));
+        Assert.That(maps[0].actions[0].bindings, Has.Count.EqualTo(3));
         Assert.That(maps[0].actions[1].bindings, Has.Count.EqualTo(1));
+        Assert.That(maps[0].actions[0].bindings[0].path, Is.EqualTo("/gamepad/leftStick"));
+        Assert.That(maps[0].actions[0].bindings[1].path, Is.EqualTo("/gamepad/rightStick"));
+        Assert.That(maps[0].actions[0].bindings[2].path, Is.Not.Null);
+        Assert.That(maps[0].actions[0].bindings[2].path, Is.Empty);
         Assert.That(maps[0].actions[0].bindings[0].groups, Is.Null);
         Assert.That(maps[0].actions[0].bindings[1].groups, Is.EqualTo("group"));
         Assert.That(maps[0].actions[0].bindings[0].processors, Is.Null);

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -48,6 +48,7 @@ however, it has to be formatted properly to pass verification tests.
   action.AddBinding("<Gamepad>/button*"); // Will only receive buttonWest, buttonEast, and buttonNorth.
   ```
   * This also means that `InputAction.controls` will now only contain any control at most once.
+- Fixed JSON serialization of action maps not preserving empty binding paths ([case 1231968](https://issuetracker.unity3d.com/issues/cloning-actionmap-through-json-converts-empty-paths-to-null-which-is-not-allowed)).
 
 ### Added
 

Packages/com.unity.inputsystem/InputSystem/Actions/InputActionMap.cs

@@ -1259,7 +1259,7 @@ public InputBinding ToBinding()
                 {
                     name = string.IsNullOrEmpty(name) ? null : name,
                     m_Id = string.IsNullOrEmpty(id) ? null : id,
-                    path = string.IsNullOrEmpty(path) ? null : path,
+                    path = path,
                     action = string.IsNullOrEmpty(action) ? null : action,
                     interactions = string.IsNullOrEmpty(interactions) ? null : interactions,
                     processors = string.IsNullOrEmpty(processors) ? null : processors,