Merge pull request #3451 from retailcoder/ObjectVariableNotSet

"Object variable not set" inspection enhancements: assignments to Nothing are now taken into consideration.

Author: retailcoder

Rubberduck.Inspections/Concrete/ObjectVariableNotSetInspection.cs

@@ -34,17 +34,20 @@ protected override IEnumerable<IInspectionResult> DoGetInspectionResults()
 
             var objectVariableNotSetReferences = referencesRequiringSetAssignment.Where(FlagIfObjectVariableNotSet);
 
-            return objectVariableNotSetReferences.Select(reference =>
+            return objectVariableNotSetReferences
+                .Select(reference =>
                 new IdentifierReferenceInspectionResult(this,
-                                     string.Format(InspectionsUI.ObjectVariableNotSetInspectionResultFormat, reference.Declaration.IdentifierName),
-                                     State,
-                                     reference));
+                    string.Format(InspectionsUI.ObjectVariableNotSetInspectionResultFormat, reference.Declaration.IdentifierName),
+                    State, reference));
         }
 
         private bool FlagIfObjectVariableNotSet(IdentifierReference reference)
         {
+            var allrefs = reference.Declaration.References;
             var letStmtContext = ParserRuleContextHelper.GetParent<VBAParser.LetStmtContext>(reference.Context);
-            return (reference.IsAssignment && letStmtContext != null);
+
+            return reference.IsAssignment && (letStmtContext != null 
+                   || allrefs.Where(r => r.IsAssignment).All(r => ParserRuleContextHelper.GetParent<VBAParser.SetStmtContext>(r.Context)?.expression()?.GetText().Equals(Tokens.Nothing, StringComparison.InvariantCultureIgnoreCase) ?? false));
         }
     }
 }

RubberduckTests/Inspections/ObjectVariableNotSetInspectionTests.cs

@@ -11,6 +11,39 @@ namespace RubberduckTests.Inspections
     [TestClass]
     public class ObjectVariableNotSetInspectionTests
     {
+        [TestMethod]
+        [TestCategory("Inspections")]
+        public void ObjectVariableNotSet_OnlyAssignedToNothing_ReturnsResult()
+        {
+            var expectResultCount = 1;
+            var input =
+                @"
+Private Sub DoSomething()
+    Dim target As Object
+    target.DoSomething ' error 91
+    Set target = Nothing
+End Sub
+";
+            AssertInputCodeYieldsExpectedInspectionResultCount(input, expectResultCount);
+        }
+
+        [TestMethod]
+        [TestCategory("Inspections")]
+        public void ObjectVariableNotSet_AlsoAssignedToNothing_ReturnsNoResult()
+        {
+            var expectResultCount = 0;
+            var input =
+                @"
+Private Sub DoSomething()
+    Dim target As Object
+    Set target = New Object
+    target.DoSomething
+    Set target = Nothing
+End Sub
+";
+            AssertInputCodeYieldsExpectedInspectionResultCount(input, expectResultCount);
+        }
+
         [TestMethod]
         [TestCategory("Inspections")]
         public void ObjectVariableNotSet_GivenIndexerObjectAccess_ReturnsNoResult()