Short circuit processing if no Listener results

Author: BZngr

Rubberduck.CodeAnalysis/Inspections/Concrete/ProcedureCanBeWrittenAsFunctionInspection.cs

@@ -26,6 +26,11 @@ public ProcedureCanBeWrittenAsFunctionInspection(RubberduckParserState state)
 
         protected override IEnumerable<IInspectionResult> DoGetInspectionResults()
         {
+            if (Listener.Contexts.Count == 0)
+            {
+                return Enumerable.Empty<IInspectionResult>();
+            }
+
             var userDeclarations = UserDeclarations.ToList();
             var builtinHandlers = State.DeclarationFinder.FindEventHandlers().ToList();
 

RubberduckTests/Inspections/ProcedureShouldBeFunctionInspectionTests.cs

@@ -10,6 +10,28 @@ namespace RubberduckTests.Inspections
     [TestFixture]
     public class ProcedureShouldBeFunctionInspectionTests
     {
+        [Test]
+        [Category("Inspections")]
+        public void ProcedureShouldBeFunction_NoArgCase_NoResults()
+        {
+            const string inputCode =
+@"
+Private foo As Long
+Private Sub Foo()
+    foo = 42
+End Sub";
+
+            var vbe = MockVbeBuilder.BuildFromSingleStandardModule(inputCode, out _);
+            using (var state = MockParser.CreateAndParse(vbe.Object))
+            {
+                var inspection = new ProcedureCanBeWrittenAsFunctionInspection(state);
+                var inspector = InspectionsHelper.GetInspector(inspection);
+                var inspectionResults = inspector.FindIssuesAsync(state, CancellationToken.None).Result;
+
+                Assert.AreEqual(0, inspectionResults.Count());
+            }
+        }
+
         [Test]
         [Category("Inspections")]
         public void ProcedureShouldBeFunction_ReturnsResult()