DYN-6527: Fix graph update for primitive input nodes that are first initialized to null

src/Engine/ProtoAssociative/CodeGen_SSA.cs

@@ -1,4 +1,4 @@
-using ProtoCore.AST.AssociativeAST;
+using ProtoCore.AST.AssociativeAST;
 using ProtoCore.DSASM;
 using ProtoCore.Utils;
 using System.Collections.Generic;
@@ -275,7 +275,11 @@ private List<AssociativeNode> BuildSSA(List<AssociativeNode> astList, ProtoCore.
                         BinaryExpressionNode bnode = (node as BinaryExpressionNode);
                         int generatedUID = ProtoCore.DSASM.Constants.kInvalidIndex;
 
-                        if (context.applySSATransform && core.Options.GenerateSSA)
+                        // Skip SSA for input ASTs that are first assigned null such as this:
+                        // a = null; (update "a") => a = <some primitive>;
+                        // SSA would break up the null AST into two assignments, which then breaks update:
+                        // a = null; (SSA) => temp = null; a = temp;
+                        if (context.applySSATransform && core.Options.GenerateSSA && !bnode.IsInputExpression)
                         {
                             int ssaID = ProtoCore.DSASM.Constants.kInvalidIndex;
                             string name = ProtoCore.Utils.CoreUtils.GenerateIdentListNameString(bnode.LeftNode);
@@ -382,53 +386,6 @@ private List<AssociativeNode> BuildSSA(List<AssociativeNode> astList, ProtoCore.
             return astList;
         }
 
-        private void DfsSSAIeentList(AssociativeNode node, ref Stack<AssociativeNode> ssaStack, ref List<AssociativeNode> astlist)
-        {
-            if (node is IdentifierListNode)
-            {
-                IdentifierListNode listNode = node as IdentifierListNode;
-
-                bool isSingleDot = !(listNode.LeftNode is IdentifierListNode) && !(listNode.RightNode is IdentifierListNode);
-                if (isSingleDot)
-                {
-                    BinaryExpressionNode bnode = BuildSSAIdentListAssignmentNode(listNode);
-                    astlist.Add(bnode);
-                    ssaStack.Push(bnode);
-                }
-                else
-                {
-                    DfsSSAIeentList(listNode.LeftNode, ref ssaStack, ref astlist);
-
-                    IdentifierListNode newListNode = node as IdentifierListNode;
-                    newListNode.Optr = Operator.dot;
-
-                    AssociativeNode leftnode = ssaStack.Pop();
-                    Validity.Assert(leftnode is BinaryExpressionNode);
-
-                    newListNode.LeftNode = (leftnode as BinaryExpressionNode).LeftNode;
-                    newListNode.RightNode = listNode.RightNode;
-
-                    BinaryExpressionNode bnode = BuildSSAIdentListAssignmentNode(newListNode);
-                    astlist.Add(bnode);
-                    ssaStack.Push(bnode);
-
-                }
-            }
-            else if (node is FunctionCallNode)
-            {
-                FunctionCallNode fcNode = node as FunctionCallNode;
-                for (int idx = 0; idx < fcNode.FormalArguments.Count; idx++)
-                {
-                    AssociativeNode arg = fcNode.FormalArguments[idx];
-
-                    Stack<AssociativeNode> ssaStack1 = new Stack<AssociativeNode>();
-                    DFSEmitSSA_AST(arg, ssaStack1, ref astlist);
-                    AssociativeNode argNode = ssaStack.Pop();
-                    fcNode.FormalArguments[idx] = argNode is BinaryExpressionNode ? (argNode as BinaryExpressionNode).LeftNode : argNode;
-                }
-            }
-        }
-
         private void DFSEmitSSA_AST(AssociativeNode node, Stack<AssociativeNode> ssaStack, ref List<AssociativeNode> astlist)
         {
             Validity.Assert(null != astlist && null != ssaStack);
@@ -488,7 +445,8 @@ private void DFSEmitSSA_AST(AssociativeNode node, Stack<AssociativeNode> ssaStac
 
                 var bnode = AstFactory.BuildAssignment(leftNode, rightNode);
                 bnode.isSSAAssignment = isSSAAssignment;
-                bnode.IsInputExpression = astBNode.IsInputExpression;
+                // TODO: SSA is not called for ASTs that are input expressions. Revisit this if there are any issues.
+                // bnode.IsInputExpression = astBNode.IsInputExpression;
 
                 astlist.Add(bnode);
                 ssaStack.Push(bnode);

src/Engine/ProtoCore/DSASM/InstructionSet.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using ProtoCore.Exceptions;
@@ -10,6 +10,7 @@ namespace ProtoCore.DSASM
     public enum Registers
     {
         RX,
+        // Register used to temporarily store primitive values for graph update cycles.
         LX,
     }
 

src/Libraries/CoreNodeModels/Enum.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;

test/DynamoCoreWpfTests/NodeExecutionUITest.cs

@@ -328,5 +328,58 @@ public void TestSelectionNodeUpdate2()
             AssertPreviewValue(tsn.GUID.ToString(), 0);
 
         }
+
+        [Test]
+        public void TestDropdownNodeUpdate()
+        {
+            var model = GetModel();
+            var tdd = new TestDropdown
+            {
+                SelectedIndex = 0
+            };
+
+            var command = new DynamoModel.CreateNodeCommand(tdd, 0, 0, true, false);
+            model.ExecuteCommand(command);
+
+            AssertPreviewValue(tdd.GUID.ToString(), "one");
+
+            tdd.SelectedIndex = 1;
+            tdd.OnNodeModified();
+
+            AssertPreviewValue(tdd.GUID.ToString(), "two");
+
+            tdd.SelectedIndex = 2;
+            tdd.OnNodeModified();
+
+            AssertPreviewValue(tdd.GUID.ToString(), "three");
+
+        }
+
+        [Test]
+        public void TestDropdownNodeUpdate1()
+        {
+            var model = GetModel();
+            var tdd = new TestDropdown();
+
+            var command = new DynamoModel.CreateNodeCommand(tdd, 0, 0, true, false);
+            model.ExecuteCommand(command);
+
+            AssertPreviewValue(tdd.GUID.ToString(), null);
+
+            tdd.SelectedIndex = 0;
+            tdd.OnNodeModified();
+
+            AssertPreviewValue(tdd.GUID.ToString(), "one");
+
+            tdd.SelectedIndex = 1;
+            tdd.OnNodeModified();
+
+            AssertPreviewValue(tdd.GUID.ToString(), "two");
+
+            tdd.SelectedIndex = 2;
+            tdd.OnNodeModified();
+
+            AssertPreviewValue(tdd.GUID.ToString(), "three");
+        }
     }
 }

test/TestUINodes/TestUINodes.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
@@ -140,4 +140,54 @@ protected override int GetModelObjectFromIdentifer(string id)
             return id.Length;
         }
     }
+
+    [NodeName("Test Dropdown Node")]
+    [NodeCategory("TestUINodes")]
+    [NodeDescription("test dropdown node")]
+    [OutPortTypes("string")]
+    [IsDesignScriptCompatible]
+    [IsVisibleInDynamoLibrary(false)]
+    public class TestDropdown : DSDropDownBase
+    {
+        public TestDropdown() : base("TestDropdown") { }
+
+
+        public override IEnumerable<AssociativeNode> BuildOutputAst(List<AssociativeNode> inputAstNodes)
+        {
+            AssociativeNode node;
+            if (SelectedIndex < 0 || SelectedIndex >= Items.Count)
+            {
+                node = AstFactory.BuildNullNode();
+                return new[] { AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), node) };
+            }
+            else
+            {
+                // get the selected items name
+                var stringNode = AstFactory.BuildStringNode((string)Items[SelectedIndex].Name);
+
+                // assign the selected name to an actual enumeration value
+                var assign = AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), stringNode);
+
+                // return the enumeration value
+                return new List<AssociativeNode> { assign };
+            }
+        }
+
+        protected override SelectionState PopulateItemsCore(string currentSelection)
+        {
+            Items.Clear();
+
+            var symbols = new[] { "one", "two", "three" };
+
+
+            foreach (var symbol in symbols)
+            {
+
+                Items.Add(new DynamoDropDownItem(symbol, symbol));
+            }
+
+            return SelectionState.Restore;
+        }
+
+    }
 }