Core - Keep the last good outputs of a node that fails to evaluate (#917)

A node that failed to evaluate reset its outputs to their default values, so a node breaking for a few frames made
everything after it jump to defaults. It now keeps the outputs of its last successful run, like before #911, and still
marks them as evaluated so it isn't evaluated again for every pin reading from it.

src/Artemis.Core.Tests/VisualScripting/NodeTests.cs

@@ -218,9 +218,9 @@ public class NodeTests : ScriptTestBase
     }
 
     [Fact]
-    public void FailingNode_InAScript_SetsItsOutputsToTheirDefaultValues()
+    public void FailingNode_InAScript_KeepsTheOutputsOfItsLastSuccessfulRun()
     {
-        // Rather than letting the value from the last run that worked flow on
+        // So a node that fails for a few frames doesn't make the script jump to default values
         NodeScript<Numeric> script = CreateScript<Numeric>();
         TestThrowingNode node = ScriptNodes.AddNode<TestThrowingNode>(script);
         script.GetExitNode().Input.ConnectTo(node.Output);
@@ -231,7 +231,7 @@ public class NodeTests : ScriptTestBase
         node.FailsOn = TestThrowingNode.FailureMode.Evaluate;
         script.Run();
 
-        script.Result.ShouldBe(new Numeric(0));
+        script.Result.ShouldBe(new Numeric(5));
         node.BrokenState.ShouldBe("Failed to evaluate");
         script.GetExitNode().BrokenState.ShouldBeNull();
     }
@@ -239,7 +239,7 @@ public class NodeTests : ScriptTestBase
     [Fact]
     public void FailingNode_InAScript_IsEvaluatedOncePerRun()
     {
-        // A failing node sets its outputs to their default values, so the other pins reading from it don't try again
+        // A failing node still marks its outputs as evaluated, so the other pins reading from it don't try again
         NodeScript<Numeric> script = CreateScript<Numeric>();
         TestNode failing = new() {OnEvaluate = _ => throw new InvalidOperationException()};
         OutputPin<Numeric> output = failing.CreateOutputPin<Numeric>();

src/Artemis.Core/VisualScripting/Nodes/Node.cs

@@ -388,10 +388,10 @@ public abstract class Node : BreakableModel, INode
         if (TryOrBreak(Evaluate, "Failed to evaluate"))
             return;
 
-        // Don't let the values of the last successful run flow on, and don't try again for every pin that reads from this
+        // Keep the values of the last successful run so a brief failure goes unnoticed, and don't try again for every pin
-        // node. Setting a value marks the pin as evaluated until the next run
+        // that reads from this node
-        foreach (Pin pin in Pins.Concat(PinCollections.SelectMany(c => c)).OfType<Pin>().Where(p => p.Direction == PinDirection.Output))
+        foreach (IPin pin in Pins.Concat(PinCollections.SelectMany(c => c)).Where(p => p.Direction == PinDirection.Output))
-            pin.SetDefaultValue();
+            pin.IsEvaluated = true;
     }
 
     /// <summary>

src/Artemis.Core/VisualScripting/Pins/OutputPin.cs

@@ -29,11 +29,6 @@ public sealed class OutputPin<T> : Pin
     /// <inheritdoc />
     public override PinDirection Direction => PinDirection.Output;
 
-    internal override void SetDefaultValue()
-    {
-        Value = default;
-    }
-
     private T? _value;
 
     /// <summary>
@@ -105,11 +100,6 @@ public sealed class OutputPin : Pin
     /// <inheritdoc />
     public override PinDirection Direction => PinDirection.Output;
 
-    internal override void SetDefaultValue()
-    {
-        Value = Type.GetDefault();
-    }
-
     private object? _value;
     private Type _type;
 

src/Artemis.Core/VisualScripting/Pins/Pin.cs

@@ -85,13 +85,6 @@ public abstract class Pin : CorePropertyChanged, IPin
         IsEvaluated = false;
     }
 
-    /// <summary>
-    ///     Sets the value of an output pin to the default value of its type, used when its node fails to evaluate
-    /// </summary>
-    internal virtual void SetDefaultValue()
-    {
-    }
-
     /// <inheritdoc />
     public void ConnectTo(IPin pin)
     {