Enable nullability in ArrayEditor

src/System.Windows.Forms.Design/src/PublicAPI.Shipped.txt

@@ -1,7 +1,7 @@
 #nullable enable
-~override System.ComponentModel.Design.ArrayEditor.CreateCollectionItemType() -> System.Type
-~override System.ComponentModel.Design.ArrayEditor.GetItems(object editValue) -> object[]
-~override System.ComponentModel.Design.ArrayEditor.SetItems(object editValue, object[] value) -> object
+override System.ComponentModel.Design.ArrayEditor.CreateCollectionItemType() -> System.Type!
+override System.ComponentModel.Design.ArrayEditor.GetItems(object? editValue) -> object![]!
+override System.ComponentModel.Design.ArrayEditor.SetItems(object? editValue, object![]? value) -> object?
 ~override System.Windows.Forms.Design.ComponentTray.GetService(System.Type serviceType) -> object
 ~override System.Windows.Forms.Design.ComponentTray.OnDragDrop(System.Windows.Forms.DragEventArgs de) -> void
 ~override System.Windows.Forms.Design.ComponentTray.OnDragEnter(System.Windows.Forms.DragEventArgs de) -> void
@@ -31,7 +31,7 @@
 ~override System.Windows.Forms.Design.ParentControlDesigner.SnapLines.get -> System.Collections.IList
 ~override System.Windows.Forms.Design.WindowsFormsDesignerOptionService.PopulateOptionCollection(System.ComponentModel.Design.DesignerOptionService.DesignerOptionCollection options) -> void
 ~static System.Windows.Forms.Design.ParentControlDesigner.InvokeCreateTool(System.Windows.Forms.Design.ParentControlDesigner toInvoke, System.Drawing.Design.ToolboxItem tool) -> void
-~System.ComponentModel.Design.ArrayEditor.ArrayEditor(System.Type type) -> void
+System.ComponentModel.Design.ArrayEditor.ArrayEditor(System.Type! type) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName, bool includeAsDesignerVerb) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName, string category) -> void

src/System.Windows.Forms.Design/src/System/ComponentModel/Design/ArrayEditor.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 namespace System.ComponentModel.Design;
 
 /// <summary>
@@ -22,12 +20,16 @@ public ArrayEditor(Type type) : base(type)
     ///  Gets or sets the data type this collection contains.
     /// </summary>
     protected override Type CreateCollectionItemType()
-        => CollectionType?.GetElementType();
+    {
+        Type? type = CollectionType.GetElementType();
+
+        return type is null ? throw new InvalidOperationException() : type;
+    }
 
     /// <summary>
     ///  Gets the items in the array.
     /// </summary>
-    protected override object[] GetItems(object editValue)
+    protected override object[] GetItems(object? editValue)
     {
         if (editValue is Array valueArray)
         {
@@ -42,7 +44,7 @@ protected override object[] GetItems(object editValue)
     /// <summary>
     ///  Sets the items in the array.
     /// </summary>
-    protected override object SetItems(object editValue, object[] value)
+    protected override object? SetItems(object? editValue, object[]? value)
     {
         if (editValue is not null and not Array)
         {

src/System.Windows.Forms.Design/src/System/ComponentModel/Design/CollectionEditor.cs

@@ -23,7 +23,7 @@ public partial class CollectionEditor : UITypeEditor
     /// <summary>
     ///  Initializes a new instance of the <see cref="CollectionEditor"/> class using the specified collection type.
     /// </summary>
-    public CollectionEditor(Type type) => CollectionType = type;
+    public CollectionEditor(Type type) => CollectionType = type.OrThrowIfNull();
 
     /// <summary>
     ///  Gets the data type of each item in the collection.

src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/ArrayEditorTests.cs

@@ -11,17 +11,8 @@ namespace System.ComponentModel.Design.Tests;
 public class ArrayEditorTests
 {
     [Theory]
-    [InlineData(typeof(object), null)]
-    [InlineData(typeof(string), null)]
+    [InlineData(typeof(string[]), typeof(string))]
     [InlineData(typeof(int[]), typeof(int))]
-    [InlineData(typeof(IList<int>), null)]
-    [InlineData(typeof(IList), null)]
-    [InlineData(typeof(ClassWithItem), null)]
-    [InlineData(typeof(ClassWithPrivateItem), null)]
-    [InlineData(typeof(ClassWithStaticItem), null)]
-    [InlineData(typeof(ClassWithItems), null)]
-    [InlineData(typeof(ClassWithPrivateItems), null)]
-    [InlineData(typeof(ClassWithStaticItems), null)]
     public void ArrayEditor_Ctor_Type(Type type, Type expectedItemType)
     {
         SubArrayEditor editor = new(type);
@@ -34,16 +25,27 @@ public void ArrayEditor_Ctor_Type(Type type, Type expectedItemType)
         Assert.Equal([expectedItemType], editor.NewItemTypes);
     }
 
+    [Theory]
+    [InlineData(typeof(object))]
+    [InlineData(typeof(string))]
+    [InlineData(typeof(IList<int>))]
+    [InlineData(typeof(IList))]
+    [InlineData(typeof(ClassWithItem))]
+    [InlineData(typeof(ClassWithPrivateItem))]
+    [InlineData(typeof(ClassWithStaticItem))]
+    [InlineData(typeof(ClassWithItems))]
+    [InlineData(typeof(ClassWithPrivateItems))]
+    [InlineData(typeof(ClassWithStaticItems))]
+    public void ArrayEditor_Ctor_Invalid_Type(Type type)
+    {
+        SubArrayEditor editor = new(type);
+        Assert.Throws<InvalidOperationException>(() => editor.CollectionItemType);
+    }
+
     [Fact]
-    public void ArrayEditor_Ctor_NullType()
+    public void ArrayEditor_Ctor_NullType_ThrowsArgumentNullException()
     {
-        SubArrayEditor editor = new(null);
-        Assert.Null(editor.CollectionItemType);
-        Assert.Null(editor.CollectionType);
-        Assert.Null(editor.Context);
-        Assert.Equal("net.ComponentModel.CollectionEditor", editor.HelpTopic);
-        Assert.False(editor.IsDropDownResizable);
-        Assert.Equal([null], editor.NewItemTypes);
+        Assert.Throws<ArgumentNullException>(() => new SubArrayEditor(null));
     }
 
     public static IEnumerable<object[]> CanRemoveInstance_TestData()
@@ -58,7 +60,7 @@ public static IEnumerable<object[]> CanRemoveInstance_TestData()
     [MemberData(nameof(CanRemoveInstance_TestData))]
     public void ArrayEditor_CanRemoveInstance_Invoke_ReturnsExpected(object value)
     {
-        SubArrayEditor editor = new(null);
+        SubArrayEditor editor = new(typeof(string[]));
         Assert.True(editor.CanRemoveInstance(value));
     }
 
@@ -77,29 +79,19 @@ public void ArrayEditor_CanRemoveInstance_InheritanceAttribute_ReturnsExpected(I
     {
         using Component component = new();
         TypeDescriptor.AddAttributes(component, attribute);
-        SubArrayEditor editor = new(null);
+        SubArrayEditor editor = new(typeof(string[]));
         Assert.Equal(expected, editor.CanRemoveInstance(component));
     }
 
     [Fact]
     public void ArrayEditor_CanSelectMultipleInstances_Invoke_ReturnsFalse()
     {
-        SubArrayEditor editor = new(null);
+        SubArrayEditor editor = new(typeof(string[]));
         Assert.True(editor.CanSelectMultipleInstances());
     }
 
     public static IEnumerable<object[]> GetDisplayText_TestData()
     {
-        yield return new object[] { null, null, string.Empty };
-        yield return new object[] { null, string.Empty, "String" };
-        yield return new object[] { null, "string", "string" };
-
-        yield return new object[] { null, new ClassWithStringName { Name = "CustomName" }, "CustomName" };
-        yield return new object[] { null, new ClassWithStringName { Name = string.Empty }, "ClassWithStringName" };
-        yield return new object[] { null, new ClassWithStringName { Name = null }, "ClassWithStringName" };
-        yield return new object[] { null, new ClassWithNonStringName { Name = 1 }, "ClassWithNonStringName" };
-        yield return new object[] { null, new ClassWithNullToString(), "ClassWithNullToString" };
-
         yield return new object[] { typeof(int), null, string.Empty };
         yield return new object[] { typeof(int), "", "String" };
         yield return new object[] { typeof(int), "value", "value" };
@@ -135,7 +127,7 @@ public void ArrayEditor_GetDisplayText_ValueDoesNotMatchCollectionType_ThrowsTar
     [CommonMemberData(typeof(CommonTestHelperEx), nameof(CommonTestHelperEx.GetITypeDescriptorContextTestData))]
     public void ArrayEditor_GetEditStyle_Invoke_ReturnsModal(ITypeDescriptorContext context)
     {
-        ArrayEditor editor = new(null);
+        ArrayEditor editor = new(typeof(string[]));
         Assert.Equal(UITypeEditorEditStyle.Modal, editor.GetEditStyle(context));
     }
 
@@ -151,7 +143,7 @@ public static IEnumerable<object[]> GetItems_TestData()
     [MemberData(nameof(GetItems_TestData))]
     public void ArrayEditor_GetItems_Invoke_ReturnsExpected(object editValue, object[] expected)
     {
-        SubArrayEditor editor = new(null);
+        SubArrayEditor editor = new(typeof(string[]));
         object[] items = editor.GetItems(editValue);
         Assert.Equal(expected, items);
         Assert.IsType(expected.GetType(), items);
@@ -162,7 +154,7 @@ public void ArrayEditor_GetItems_Invoke_ReturnsExpected(object editValue, object
     [CommonMemberData(typeof(CommonTestHelperEx), nameof(CommonTestHelperEx.GetITypeDescriptorContextTestData))]
     public void ArrayEditor_GetPaintValueSupported_Invoke_ReturnsFalse(ITypeDescriptorContext context)
     {
-        ArrayEditor editor = new(null);
+        ArrayEditor editor = new(typeof(string[]));
         Assert.False(editor.GetPaintValueSupported(context));
     }
 
@@ -202,17 +194,6 @@ public void ArrayEditor_SetItems_InvokeNonArrayValue_ReturnsExpected(object edit
         Assert.Same(expected, editor.SetItems(editValue, value));
     }
 
-    [Theory]
-    [InlineData(typeof(object))]
-    [InlineData(null)]
-    public void ArrayEditor_SetItems_NullCollectionItemType_ThrowsArgumentNullException(Type type)
-    {
-        SubArrayEditor editor = new(type);
-        Assert.Null(editor.CollectionItemType);
-        Assert.Throws<ArgumentNullException>("elementType", () => editor.SetItems(null, Array.Empty<object>()));
-        Assert.Throws<ArgumentNullException>("elementType", () => editor.SetItems(Array.Empty<object>(), Array.Empty<object>()));
-    }
-
     private class SubArrayEditor : ArrayEditor
     {
         public SubArrayEditor(Type type) : base(type)