[iOS] Allow empty format in DatePicker

Xamarin.Forms.ControlGallery.iOS/Xamarin.Forms.ControlGallery.iOS.csproj

@@ -146,6 +146,7 @@
     <Compile Include="_10337CustomRenderer.cs" />
     <Compile Include="_11132CustomRenderer.cs" />
     <Compile Include="CustomRenderers\_12372CustomRenderer.cs" />
+    <Compile Include="_13577CustomRenderer.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Xamarin.Forms.Controls\Xamarin.Forms.Controls.csproj">

Xamarin.Forms.ControlGallery.iOS/_13577CustomRenderer.cs

@@ -0,0 +1,78 @@
+using System;
+using System.Collections.Generic;
+using CoreGraphics;
+using UIKit;
+using Xamarin.Forms;
+using Xamarin.Forms.ControlGallery.iOS;
+using Xamarin.Forms.Controls.Issues;
+using Xamarin.Forms.Platform.iOS;
+
+[assembly: ExportRenderer(typeof(NullableDatePicker), typeof(_13577CustomRenderer))]
+namespace Xamarin.Forms.ControlGallery.iOS
+{
+	public class _13577CustomRenderer : DatePickerRenderer
+    {
+        public NullableDatePicker Entry => Element as NullableDatePicker;
+
+        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.DatePicker> e)
+        {
+            base.OnElementChanged(e);
+
+            if (Control != null)
+            {
+                AddClearButton();
+
+                // Border style; Remove corner radius and change colors
+                Control.BorderStyle = UITextBorderStyle.Line;
+                Control.Layer.CornerRadius = 0;
+                Control.Layer.BorderWidth = 1;
+
+                // Add padding
+                Control.LeftView = new UIView(new CGRect(0, 0, 10, 0));
+                Control.LeftViewMode = UITextFieldViewMode.Always;
+                Control.RightView = new UIView(new CGRect(0, 0, 10, 0));
+                Control.RightViewMode = UITextFieldViewMode.Always;
+
+                if (e.NewElement != null)
+                {
+                    try
+                    {
+                        if (UIDevice.CurrentDevice.CheckSystemVersion(14, 0))
+                        {
+                            UIDatePicker picker = (UIDatePicker)Control.InputView;
+                            picker.PreferredDatePickerStyle = UIDatePickerStyle.Wheels;
+                        }
+                    }
+                    catch (Exception)
+                    {
+                        // Do nothing
+                    }
+                }
+            }
+        }
+
+        private void AddClearButton()
+        {
+            if (Control.InputAccessoryView is UIToolbar originalToolbar && originalToolbar.Items.Length <= 2)
+            {
+                var clearButton = new UIBarButtonItem("Delete", UIBarButtonItemStyle.Plain, (sender, ev) =>
+                {
+                    NullableDatePicker baseDatePicker = this.Element as NullableDatePicker;
+                    Element.Unfocus();
+                    baseDatePicker.CleanDate();
+                });
+
+                var newItems = new List<UIBarButtonItem>();
+                foreach (var item in originalToolbar.Items)
+                {
+                    newItems.Add(item);
+                }
+
+                newItems.Insert(0, clearButton);
+
+                originalToolbar.Items = newItems.ToArray();
+                originalToolbar.SetNeedsDisplay();
+            }
+        }
+    }
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13577.xaml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<local:TestContentPage
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:d="http://xamarin.com/schemas/2014/forms/design"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    Title="Test 13577" xmlns:local="using:Xamarin.Forms.Controls"
+    xmlns:issues="using:Xamarin.Forms.Controls.Issues"
+    x:Class="Xamarin.Forms.Controls.Issues.Issue13577">
+    <StackLayout>
+        <Label
+            Padding="12"
+            BackgroundColor="Black"
+            TextColor="White"
+            Text="If you can clear the selected Date, the test has passed."/>
+        <issues:NullableDatePicker
+            Format="dd-MM-yyyy"
+            NullableDate="{Binding NullableDate}" />
+    </StackLayout>
+</local:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13577.xaml.cs

@@ -0,0 +1,126 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 13577,
+        "[Bug][DatePicker][XF5] DatePicker empty format now invalid",
+		PlatformAffected.iOS)]
+	public partial class Issue13577 : TestContentPage
+	{
+		public Issue13577()
+		{
+#if APP
+			InitializeComponent();
+#endif
+		}
+
+		protected override void Init()
+        {
+            BindingContext = new Issue13577ViewModel();
+        }
+	}
+
+    public class Issue13577ViewModel
+    {
+        public Issue13577ViewModel()
+        {
+            NullableDate = null;
+        }
+
+        public DateTime? NullableDate { get; set; }
+    }
+
+    public class NullableDatePicker : Xamarin.Forms.DatePicker
+    {
+        public static readonly BindableProperty NullableDateProperty = BindableProperty.Create("NullableDate", typeof(DateTime?), typeof(NullableDatePicker), null, BindingMode.TwoWay);
+
+        public DateTime? NullableDate
+        {
+            get
+            {
+                return (DateTime?)GetValue(NullableDateProperty);
+            }
+            set
+            {
+                if (value != NullableDate)
+                {
+                    SetValue(NullableDateProperty, value);
+                    UpdateDate();
+                }
+            }
+        }
+
+        public void CleanDate()
+        {
+            NullableDate = null;
+            UpdateDate();
+        }
+
+        public void AssignValue()
+        {
+            NullableDate = Date;
+            UpdateDate();
+        }
+
+        protected override void OnBindingContextChanged()
+        {
+            base.OnBindingContextChanged();
+            UpdateDate();
+        }
+
+        protected override void OnPropertyChanged(string propertyName = null)
+        {
+            base.OnPropertyChanged(propertyName);
+
+            if (propertyName == IsFocusedProperty.PropertyName)
+            {
+                if (!IsFocused)
+                {
+                    OnPropertyChanged(DateProperty.PropertyName);
+                }
+            }
+
+            if (propertyName == DateProperty.PropertyName)
+            {
+                NullableDate = Date;
+            }
+
+            if (propertyName == NullableDateProperty.PropertyName)
+            {
+                if (NullableDate.HasValue)
+                {
+                    Date = NullableDate.Value;
+                    Format = "dd-MM-yyyy";
+                }
+                else
+                {
+                    Format = "  ";
+                }
+            }
+        }
+
+        private void UpdateDate()
+        {
+            if (NullableDate.HasValue)
+            {
+                Date = NullableDate.Value;
+                Format = "dd-MM-yyyy";
+            }
+            else
+            {
+                Format = "  ";
+            }
+        }
+    }
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -1788,6 +1788,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)FrameBackgroundIssue.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14664.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14192.xaml.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue13577.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14505.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue14505-II.cs" />
   </ItemGroup>
@@ -2255,6 +2256,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue14192.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue13577.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla27417Xaml.xaml">

Xamarin.Forms.Platform.iOS/Renderers/DatePickerRenderer.cs

@@ -1,7 +1,6 @@
 using System;
 using System.ComponentModel;
 using System.Globalization;
-using System.Linq;
 using Foundation;
 using UIKit;
 using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
@@ -169,10 +168,12 @@ void UpdateDateFromModel(bool animate)
 				_picker.SetDate(Element.Date.ToNSDate(), animate);
 
 			// Can't use Element.Format because it won't display the correct format if the region and language are set differently
-			if (string.IsNullOrWhiteSpace(Element.Format) || Element.Format.Equals("d") || Element.Format.Equals("D"))
+			if (Element.Format.Equals("d") || Element.Format.Equals("D"))
 			{
-				NSDateFormatter dateFormatter = new NSDateFormatter();
-				dateFormatter.TimeZone = NSTimeZone.FromGMT(0);
+				NSDateFormatter dateFormatter = new NSDateFormatter
+				{
+					TimeZone = NSTimeZone.FromGMT(0)
+				};
 
 				if (Element.Format?.Equals("D") == true)
 				{