Resolved all reviews and change request.

Added tests for `CanExecute`.

Author: Mrblackey

Rubberduck.Core/UI/CodeExplorer/Commands/CodeExplorerExtractInterfaceCommand.cs

@@ -1,5 +1,6 @@
 using Rubberduck.Navigation.CodeExplorer;
 using Rubberduck.Parsing.VBA;
+using Rubberduck.Refactorings.Exceptions;
 using Rubberduck.Refactorings.ExtractInterface;
 using Rubberduck.UI.Command.Refactorings.Notifiers;
 using Rubberduck.VBEditor.Events;
@@ -30,6 +31,7 @@ public CodeExplorerExtractInterfaceCommand(
             _refactoring = refactoring;
             _failureNotifier = failureNotifier;
             AddToCanExecuteEvaluation(SpecialEvaluateCanExecute);
+            AddToOnExecuteEvaluation(FurtherCanExecuteEvaluation);
         }
 
         public sealed override IEnumerable<Type> ApplicableNodeTypes => ApplicableNodes;
@@ -38,19 +40,28 @@ private bool SpecialEvaluateCanExecute(object parameter)
         {
             return _state.Status == ParserState.Ready &&
                    parameter is CodeExplorerComponentViewModel node &&
-                   ExtractInterfaceRefactoring.CanExecute((RubberduckParserState)_state, node.QualifiedSelection.Value.QualifiedName);
+                   _refactoring.CanExecute((RubberduckParserState)_state, node.QualifiedSelection.Value.QualifiedName);
+        }
+
+        private bool FurtherCanExecuteEvaluation(object parameter)
+        {
+            return _state.Status == ParserState.Ready &&
+                parameter is CodeExplorerItemViewModel node &&
+                node.Declaration != null;
         }
 
         protected override void OnExecute(object parameter)
         {
-            if (_state.Status != ParserState.Ready ||
-                !(parameter is CodeExplorerItemViewModel node) ||
-                node.Declaration == null)
+            try
             {
-                return;
+                _refactoring.Refactor(((CodeExplorerItemViewModel)parameter).Declaration);
+            }
+            catch (RefactoringAbortedException)
+            { }
+            catch (RefactoringException exception)
+            {
+                _failureNotifier.Notify(exception);
             }
-
-            _refactoring.Refactor(node.Declaration);
         }
     }
 }

Rubberduck.Core/UI/Command/Refactorings/RefactorExtractInterfaceCommand.cs

@@ -32,7 +32,7 @@ private bool SpecializedEvaluateCanExecute(object parameter)
             {
                 return false;
             }
-            return ExtractInterfaceRefactoring.CanExecute(_state, activeSelection.Value.QualifiedName);
+            return ((ExtractInterfaceRefactoring)Refactoring).CanExecute(_state, activeSelection.Value.QualifiedName);
         }
 
         private static readonly IReadOnlyList<DeclarationType> ModuleTypes = new[]

Rubberduck.Refactorings/ExtractInterface/ExtractInterfaceRefactoring.cs

@@ -137,7 +137,7 @@ private string GetInterfaceModuleBody(ExtractInterfaceModel model)
             DeclarationType.UserForm
         };
 
-        public static bool CanExecute(RubberduckParserState state, QualifiedModuleName qualifiedName)
+        public bool CanExecute(RubberduckParserState state, QualifiedModuleName qualifiedName)
         {
             var interfaceClass = state.AllUserDeclarations.SingleOrDefault(item =>
                 item.QualifiedName.QualifiedModuleName.Equals(qualifiedName)

RubberduckTests/CodeExplorer/CodeExplorerViewModelTests.cs

@@ -245,6 +245,31 @@ public bool AddUserDocument_CanExecuteBasedOnProjectType(ProjectType projectType
             }
         }
 
+        [Category("Code Explorer")]
+        [Test]
+        [TestCase(ComponentType.ActiveXDesigner, ExpectedResult = true)]
+        [TestCase(ComponentType.ClassModule, ExpectedResult = true)]
+        [TestCase(ComponentType.ComComponent, ExpectedResult = true)]
+        [TestCase(ComponentType.DocObject, ExpectedResult = true)]
+        [TestCase(ComponentType.Document, ExpectedResult = true)]
+        [TestCase(ComponentType.MDIForm, ExpectedResult = true)]
+        [TestCase(ComponentType.PropPage, ExpectedResult = true)]
+        [TestCase(ComponentType.RelatedDocument, ExpectedResult = false, Ignore = "Module doesn't contain members")]
+        [TestCase(ComponentType.ResFile, ExpectedResult = false, Ignore = "Module doesn't contain members")]
+        [TestCase(ComponentType.StandardModule, ExpectedResult = false)]
+        [TestCase(ComponentType.Undefined, ExpectedResult = true)]
+        [TestCase(ComponentType.UserControl, ExpectedResult = true)]
+        [TestCase(ComponentType.UserForm, ExpectedResult = true)]
+        [TestCase(ComponentType.VBForm, ExpectedResult = true)]
+        public bool RefactorExtractInterface_CanExecuteBasedOnComponentType(ComponentType componentType)
+        {
+            using (var explorer = new MockedCodeExplorer(ProjectType.HostProject, componentType, @"Public Sub Foo():  MsgBox """":End Sub ")
+                .ImplementExtractIntercaceCommand().SelectFirstModule())
+            {
+                return explorer.ViewModel.CodeExplorerExtractInterfaceCommand.CanExecute(explorer.ViewModel.SelectedItem);
+            }
+        }
+
         [Category("Code Explorer")]
         [Test]
         public void AddTestModule()

RubberduckTests/CodeExplorer/MockedCodeExplorer.cs

@@ -403,6 +403,15 @@ public MockedCodeExplorer ImplementIndenterCommand()
             return this;
         }
 
+        public MockedCodeExplorer ImplementExtractIntercaceCommand()
+        {
+            ViewModel.CodeExplorerExtractInterfaceCommand = new CodeExplorerExtractInterfaceCommand(
+                new Rubberduck.Refactorings.ExtractInterface.ExtractInterfaceRefactoring(
+                    State, State, null, null, null),
+                State, null, VbeEvents.Object);
+            return this;
+        }
+
         public MockedCodeExplorer ConfigureSaveDialog(string path, DialogResult result)
         {
             SaveDialog.Setup(o => o.FileName).Returns(path);