MahApps.Metro: Invalid behavior of the icon in row header in data grid when record implements INotifyDataErrorInfo

Description

1. Add DataGrid
2. Set as ItemsSource ObservableCollection with records which implement INotifyDataErrorInfo and INotifyPropertyChanged and with errors after initialization
3. Run app
4. Textbox has red border but icon is missing (strange but I can live with that)
5. Double click on cell (icon in row header is shown)
6. fix value and hit enter
7. Textbox hasn’t got red border (PASS) but icon with tooltip with original error is still there (FAIL)

Am I implemented it incorrectly? Or it’s an issue in header style?

Environment

• .NET Framework 4.7.2
• Windows 10 1903

Nuget libraries

• MahApps.Metro 1.6.5
• FluentValidation 8.5.1 (for validation)
• Fody 6.0.4
• PropertyChanged.Fody 3.1.3 (for autiomatic notifications)
• Caliburn.Micro 3.2.0 (only base class)

Code

using Caliburn.Micro;
using FluentValidation;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
namespace WpfDataGridValidation
{
public class MainWindowViewModel : Conductor<IScreen>.Collection.AllActive
{
    public MainWindowViewModel()
    {
        var validator = new MyRecordValidator();
        var record = new MyRecord(validator);
        Records = new ObservableCollection<MyRecord>(Enumerable.Repeat(record, 1));
    }

    public ObservableCollection<MyRecord> Records { get; set; }
}

public class MyRecord : Caliburn.Micro.PropertyChangedBase, INotifyDataErrorInfo
{
    private readonly FluentValidation.AbstractValidator<MyRecord> _validator;

    public MyRecord(FluentValidation.AbstractValidator<MyRecord> validator)
    {
        _validator = validator;
        Validate();
    }

    public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;

    public bool HasErrors => Errors.Any();

    public IEnumerable GetErrors(string propertyName)
    {
        if (string.IsNullOrEmpty(propertyName))
            return null;
        if (Errors.TryGetValue(propertyName, out List<string> value))
            return value;
        return Enumerable.Empty<string>();
    }

    private void Validate()
    {
        if (_validator == null)
            return;
        var previousKeys = Errors.Select(x => x.Key).ToList();
        Errors = _validator.Validate(this)
            .Errors
            .GroupBy(x => x.PropertyName)
            .ToDictionary(x => x.Key, x => x.Select(y => y.ErrorMessage).ToList());
        if (ErrorsChanged == null)
            return;
        foreach (var key in Errors.Keys)
            ErrorsChanged.Invoke(this, new DataErrorsChangedEventArgs(key));
        foreach (var key in previousKeys.Except(Errors.Select(x => x.Key)))
            ErrorsChanged.Invoke(this, new DataErrorsChangedEventArgs(key));
    }

    public override void NotifyOfPropertyChange([CallerMemberName] string propertyName = null)
    {
        if (propertyName != null && propertyName != nameof(Errors) && propertyName != nameof(HasErrors))
            Validate();
        base.NotifyOfPropertyChange(propertyName);
    }

    public string Name { get; set; }
    public Dictionary<string, List<string>> Errors { get; private set; } = new Dictionary<string, List<string>>();
}

public class MyRecordValidator : FluentValidation.AbstractValidator<MyRecord>
{
    public MyRecordValidator()
    {
        RuleFor(x => x.Name).NotEmpty();
    }
}
}

MainWindow view

<Window x:Class="WpfDataGridValidation.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfDataGridValidation"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <DataGrid
            x:Name="dataGrid"
            ItemsSource="{Binding Records}"
            CanUserAddRows="False"
            CanUserSortColumns="False"
            CanUserResizeColumns="False"
            CanUserResizeRows="False"
            CanUserReorderColumns="False"    
            SelectionMode="Single"
            SelectionUnit="Cell"
            AutoGenerateColumns="False"
            VerticalAlignment="Top"
            HorizontalAlignment="Left"
            GridLinesVisibility="All"
            VirtualizingStackPanel.VirtualizationMode="Standard"
            HeadersVisibility="All"
            RowHeaderWidth="40"
            >
            <DataGrid.Columns>
                <DataGridTextColumn Header="Name" Binding="{Binding Name, NotifyOnSourceUpdated=True, NotifyOnTargetUpdated=True, NotifyOnValidationError=True,ValidatesOnNotifyDataErrors=True}"/>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

MainWindow bode behind

using System.Windows;

namespace WpfDataGridValidation
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new MainWindowViewModel();
        }
    }
}

App.xaml

<Application x:Class="WpfDataGridValidation.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:WpfDataGridValidation"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Green.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>