Feature extension and testcase for new ModelObservableValidation (#59)

* extension method for overload with property lambda

* testcase for new functionality

Author: jasonwurzel

src/ReactiveUI.Validation.Tests/API/ApiApprovalTests.ValidationProject.net472.approved.txt

@@ -134,6 +134,8 @@ namespace ReactiveUI.Validation.Extensions
             where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
         public static ReactiveUI.Validation.Helpers.ValidationHelper ValidationRule<TViewModel>(this TViewModel viewModel, System.Func<TViewModel, System.IObservable<bool>> viewModelObservableProperty, System.Func<TViewModel, bool, string> messageFunc)
             where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
+        public static ReactiveUI.Validation.Helpers.ValidationHelper ValidationRule<TViewModel, TViewModelProp>(this TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TViewModelProp>> viewModelProperty, System.Func<TViewModel, System.IObservable<bool>> viewModelObservableProperty, System.Func<TViewModel, bool, string> messageFunc)
+            where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
     }
     public class static ValidationContextExtensions
     {

src/ReactiveUI.Validation.Tests/API/ApiApprovalTests.ValidationProject.netcoreapp2.1.approved.txt

@@ -134,6 +134,8 @@ namespace ReactiveUI.Validation.Extensions
             where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
         public static ReactiveUI.Validation.Helpers.ValidationHelper ValidationRule<TViewModel>(this TViewModel viewModel, System.Func<TViewModel, System.IObservable<bool>> viewModelObservableProperty, System.Func<TViewModel, bool, string> messageFunc)
             where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
+        public static ReactiveUI.Validation.Helpers.ValidationHelper ValidationRule<TViewModel, TViewModelProp>(this TViewModel viewModel, System.Linq.Expressions.Expression<System.Func<TViewModel, TViewModelProp>> viewModelProperty, System.Func<TViewModel, System.IObservable<bool>> viewModelObservableProperty, System.Func<TViewModel, bool, string> messageFunc)
+            where TViewModel : ReactiveUI.ReactiveObject, ReactiveUI.Validation.Abstractions.IValidatableViewModel { }
     }
     public class static ValidationContextExtensions
     {

src/ReactiveUI.Validation.Tests/Models/IndeiTestViewModel.cs

@@ -9,6 +9,7 @@ namespace ReactiveUI.Validation.Tests.Models
     public class IndeiTestViewModel : ReactiveValidationObject<IndeiTestViewModel>
     {
         private string _name;
+        private string _otherName;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="IndeiTestViewModel"/> class.
@@ -26,5 +27,14 @@ public string Name
             get => _name;
             set => this.RaiseAndSetIfChanged(ref _name, value);
         }
+
+        /// <summary>
+        /// Gets or sets get the Name.
+        /// </summary>
+        public string OtherName
+        {
+            get => _otherName;
+            set => this.RaiseAndSetIfChanged(ref _otherName, value);
+        }
     }
 }

src/ReactiveUI.Validation.Tests/NotifyDataErrorInfoTests.cs

@@ -1,5 +1,6 @@
 using System.ComponentModel;
 using System.Linq;
+using System.Reactive.Linq;
 using ReactiveUI.Validation.Components;
 using ReactiveUI.Validation.Extensions;
 using ReactiveUI.Validation.Tests.Models;
@@ -121,5 +122,42 @@ public void ShouldFireErrorsChangedEventWhenValidationStateChanges()
             Assert.NotNull(arguments);
             Assert.Equal(string.Empty, arguments.PropertyName);
         }
+
+        /// <summary>
+        /// Using ModelObservableValidation with NotifyDataErrorInfo should return errors when associated property changes.
+        /// </summary>
+        [Fact]
+        public void ShouldDeliverErrorsWhenModelObservableValidationTriggers()
+        {
+            var viewModel = new IndeiTestViewModel();
+
+            string namesShouldMatchMessage = "names should match.";
+            var validation = new ModelObservableValidation<IndeiTestViewModel, string>(
+                viewModel,
+                vm => vm.OtherName,
+                vm => vm.WhenAnyValue(
+                        m => m.Name,
+                        m => m.OtherName,
+                        (n, on) => new { n, on })
+                    .Select(bothNames => bothNames.n == bothNames.on),
+                (_, isValid) => isValid ? string.Empty : namesShouldMatchMessage);
+
+            viewModel.ValidationContext.Add(validation);
+
+            Assert.False(viewModel.HasErrors);
+            Assert.True(viewModel.ValidationContext.IsValid);
+            Assert.Single(viewModel.ValidationContext.Validations);
+            Assert.Empty(viewModel.GetErrors(nameof(viewModel.Name)).Cast<string>());
+            Assert.Empty(viewModel.GetErrors(nameof(viewModel.OtherName)).Cast<string>());
+
+            viewModel.Name = "JoJo";
+            viewModel.OtherName = "NoNo";
+
+            Assert.True(viewModel.HasErrors);
+            Assert.Empty(viewModel.GetErrors(nameof(viewModel.Name)).Cast<string>());
+            Assert.Single(viewModel.GetErrors(nameof(viewModel.OtherName)).Cast<string>());
+            Assert.Single(validation.Text);
+            Assert.Equal(namesShouldMatchMessage, validation.Text.Single());
+        }
     }
 }

src/ReactiveUI.Validation/Extensions/SupportsValidationExtensions.cs

@@ -103,6 +103,34 @@ public static ValidationHelper ValidationRule<TViewModel>(
             return new ValidationHelper(validation);
         }
 
+        /// <summary>
+        /// Setup a validation rule with a general observable indicating validity.
+        /// </summary>
+        /// <typeparam name="TViewModel">ViewModel type.</typeparam>
+        /// <typeparam name="TViewModelProp">ViewModel property type.</typeparam>
+        /// <param name="viewModel">ViewModel instance.</param>
+        /// <param name="viewModelProperty">ViewModel property referenced in viewModelObservableProperty.</param>
+        /// <param name="viewModelObservableProperty">Func to define if the viewModel is valid or not.</param>
+        /// <param name="messageFunc">Func to define the validation error message based on the viewModel and viewModelObservableProperty values.</param>
+        /// <returns>Returns a <see cref="ValidationHelper"/> object.</returns>
+        /// <remarks>
+        /// It should be noted that the observable should provide an initial value, otherwise that can result
+        /// in an inconsistent performance.
+        /// </remarks>
+        public static ValidationHelper ValidationRule<TViewModel, TViewModelProp>(
+            this TViewModel viewModel,
+            Expression<Func<TViewModel, TViewModelProp>> viewModelProperty,
+            Func<TViewModel, IObservable<bool>> viewModelObservableProperty,
+            Func<TViewModel, bool, string> messageFunc)
+            where TViewModel : ReactiveObject, IValidatableViewModel
+        {
+            var validation = new ModelObservableValidation<TViewModel, TViewModelProp>(viewModel, viewModelProperty, viewModelObservableProperty, messageFunc);
+
+            viewModel.ValidationContext.Add(validation);
+
+            return new ValidationHelper(validation);
+        }
+
         /// <summary>
         /// Gets an observable for the validity of the ViewModel.
         /// </summary>
@@ -115,4 +143,4 @@ public static IObservable<bool> IsValid<TViewModel>(this TViewModel viewModel)
             return viewModel?.ValidationContext.Valid;
         }
     }
-}
+}