Enforce maximum 1 MDI Form per project

Author: Andrew Mansell

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

@@ -2,22 +2,54 @@
 using Rubberduck.Navigation.CodeExplorer;
 using Rubberduck.UI.Command;
 using Rubberduck.VBEditor.SafeComWrappers;
+using Rubberduck.VBEditor.SafeComWrappers.Abstract;
 
 namespace Rubberduck.UI.CodeExplorer.Commands
 {
     [CodeExplorerCommand]
     public class AddMDIFormCommand : CommandBase
     {
+        private readonly IVBE _vbe;
         private readonly AddComponentCommand _addComponentCommand;
 
-        public AddMDIFormCommand(AddComponentCommand addComponentCommand) : base(LogManager.GetCurrentClassLogger())
+        public AddMDIFormCommand(IVBE vbe, AddComponentCommand addComponentCommand) : base(LogManager.GetCurrentClassLogger())
         {
+            _vbe = vbe;
             _addComponentCommand = addComponentCommand;
         }
 
         protected override bool EvaluateCanExecute(object parameter)
         {
-            return _addComponentCommand.CanAddComponent(parameter as CodeExplorerItemViewModel, new[] {ProjectType.StandardExe, ProjectType.ActiveXExe});
+            var node = parameter as CodeExplorerItemViewModel;
+            while (node != null && !(node is ICodeExplorerDeclarationViewModel))
+            {
+                node = node.Parent;
+            }
+            var project = (node as ICodeExplorerDeclarationViewModel)?.Declaration?.Project;
+
+            if (project == null  && _vbe.ProjectsCount == 1)
+            {
+                project = _vbe.VBProjects[1];
+            }
+
+            if (project == null)
+            {
+                return false;
+            }
+
+            foreach (var component in project.VBComponents)
+            {
+                using (component)
+                {
+                    if (component.Type == ComponentType.MDIForm)
+                    {
+                        // Only one MDI Form allowed per project
+                        return false;
+                    }
+                }                    
+            }            
+
+            return _addComponentCommand.CanAddComponent(parameter as CodeExplorerItemViewModel, new[] { ProjectType.StandardExe, ProjectType.ActiveXExe });
         }
 
         protected override void OnExecute(object parameter)

RubberduckTests/CodeExplorer/CodeExplorerTests.cs

@@ -337,7 +337,7 @@ public void AddMDIForm()
             var vbe = builder.AddProject(project.Build()).Build();
             var vbeEvents = MockVbeEvents.CreateMockVbeEvents(vbe);
 
-            var commands = new List<CommandBase> { new AddMDIFormCommand(new AddComponentCommand(vbe.Object)) };
+            var commands = new List<CommandBase> { new AddMDIFormCommand(vbe.Object, new AddComponentCommand(vbe.Object)) };
 
             var projectRepository = new ProjectsRepository(vbe.Object);
             var uiDispatcher = new Mock<IUiDispatcher>();
@@ -375,7 +375,7 @@ public bool AddMDIForm_CanExecuteBasedOnProjectType(ProjectType projectType)
             var vbe = builder.AddProject(project.Build()).Build();
             var vbeEvents = MockVbeEvents.CreateMockVbeEvents(vbe);
 
-            var commands = new List<CommandBase> { new AddMDIFormCommand(new AddComponentCommand(vbe.Object)) };
+            var commands = new List<CommandBase> { new AddMDIFormCommand(vbe.Object, new AddComponentCommand(vbe.Object)) };
 
             var projectRepository = new ProjectsRepository(vbe.Object);
             var uiDispatcher = new Mock<IUiDispatcher>();
@@ -394,6 +394,37 @@ public bool AddMDIForm_CanExecuteBasedOnProjectType(ProjectType projectType)
             }
         }
 
+        [Category("Code Explorer")]
+        [Test]
+        public void AddMDIForm_CannotExecuteIfProjectAlreadyHasMDIForm()
+        {
+            var builder = new MockVbeBuilder();
+            var project = builder.ProjectBuilder("TestProject1", ProjectProtection.Unprotected, ProjectType.StandardExe)
+                .AddComponent("MDIForm1", ComponentType.MDIForm, "");
+
+
+            var vbe = builder.AddProject(project.Build()).Build();
+            var vbeEvents = MockVbeEvents.CreateMockVbeEvents(vbe);
+
+            var commands = new List<CommandBase> { new AddMDIFormCommand(vbe.Object, new AddComponentCommand(vbe.Object)) };
+
+            var projectRepository = new ProjectsRepository(vbe.Object);
+            var uiDispatcher = new Mock<IUiDispatcher>();
+
+            using (var state = new RubberduckParserState(vbe.Object, projectRepository, new DeclarationFinderFactory(), vbeEvents.Object))
+            {
+                var vm = new CodeExplorerViewModel(new FolderHelper(state), state, commands, _generalSettingsProvider.Object, _windowSettingsProvider.Object, uiDispatcher.Object, vbe.Object);
+
+                var parser = MockParser.Create(vbe.Object, state, projectRepository);
+                parser.Parse(new CancellationTokenSource());
+                if (parser.State.Status >= ParserState.Error) { Assert.Inconclusive("Parser Error"); }
+
+                vm.SelectedItem = vm.Projects.First().Items.First().Items.First();
+
+                Assert.IsFalse(vm.AddMDIFormCommand.CanExecute(vm.SelectedItem));
+            }
+        }
+
         [Category("Code Explorer")]
         [Test]
         public void AddUserControlForm()