Add payload and parameter validations

Author: jicking

JixMinApi/Features/Todo/Commands/CreateTodoCommand.cs

@@ -1,5 +1,4 @@
-using JixMinApi.Shared;
-using MediatR;
+using MediatR;
 
 namespace JixMinApi.Features.Todo.Commands;
 
@@ -14,7 +13,11 @@ public class CreateTodoCommandHandler : IRequestHandler<CreateTodoCommand, Resul
 
     public async Task<Result<TodoDto>> Handle(CreateTodoCommand request, CancellationToken cancellationToken)
     {
-        // add validation then set Result.ValidationErrors
+        // simple inline validation, if needed validate using behaviors https://github.com/jbogard/MediatR/wiki/Behaviors
+        if (string.IsNullOrEmpty(request.input.Name))
+        {
+            return new Result<TodoDto>([new KeyValuePair<string, string[]>("Name", ["Must not be empty."])]);
+        }
 
         var todo = new Todo()
         {
@@ -23,21 +26,13 @@ public async Task<Result<TodoDto>> Handle(CreateTodoCommand request, Cancellatio
             DateCreated = DateTimeOffset.UtcNow,
         };
 
-        try
-        {
-            await _db.Todos.AddAsync(todo);
-            await _db.SaveChangesAsync();
+        await _db.Todos.AddAsync(todo);
+        await _db.SaveChangesAsync();
 
-            _logger.LogInformation($"Todo {todo.Id} is successfully created");
-            // publish mediatr notification
-            // await _mediator.Publish(new TodoCreatedNotification(todo), cancellationToken);
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError($"Todo {todo.Id} failed due to an error: {ex.Message}",
-            todo.Id, ex.Message);
-            return new Result<TodoDto>(ex);
-        }
+        _logger.LogInformation($"Todo {todo.Id} is successfully created");
+
+        // publish mediatr notification https://github.com/jbogard/MediatR/wiki#notifications
+        // await _mediator.Publish(new TodoCreatedNotification(todo), cancellationToken);
 
         return new Result<TodoDto>(todo.ToDto());
     }

JixMinApi/Features/Todo/Result.cs

@@ -0,0 +1,36 @@
+namespace JixMinApi.Features.Todo;
+
+
+public class Result<T>
+{
+    public bool IsSuccess { get; init; }
+    public T? Value { get; init; }
+
+    public bool HasValidationError { get; init; }
+    public IReadOnlyList<KeyValuePair<string, string[]>> ValidationErrors { get; init; } = [];
+
+    //public bool IsError { get; init; }
+    //public Exception? Exception { get; init; }
+
+
+    public Result(T value)
+    {
+        Value = value;
+        IsSuccess = true;
+    }
+
+    public Result(IEnumerable<KeyValuePair<string, string[]>> validationErrors)
+    {
+        ValidationErrors = validationErrors.ToList();
+        HasValidationError = true;
+    }
+
+    public Result(string field, string validationErrorMessage)
+    {
+        List<KeyValuePair<string, string[]>> validationErrors
+            = [new KeyValuePair<string, string[]>(field, [validationErrorMessage])];
+        ValidationErrors = validationErrors;
+        HasValidationError = true;
+    }
+}
+

JixMinApi/Features/Todo/TodoEndpoints.cs

@@ -39,13 +39,13 @@ public static void MapTodoEndpoints(this WebApplication app)
 
         group.MapGet("/{id}", GetTodoByIdAsync)
             .Produces<TodoDto>(StatusCodes.Status200OK)
-            .Produces<ValidationErrorDto>(StatusCodes.Status400BadRequest)
+            .Produces<HttpValidationProblemDetails>(StatusCodes.Status400BadRequest)
             .Produces(StatusCodes.Status404NotFound);
 
         group.MapPost("/", CreateTodoAsync)
             .Accepts<TodoCreateDto>(MediaTypeNames.Application.Json)
             .Produces<TodoDto>(StatusCodes.Status201Created)
-            .Produces<ValidationErrorDto>(StatusCodes.Status400BadRequest);
+            .Produces<HttpValidationProblemDetails>(StatusCodes.Status400BadRequest);
 
         //group.MapDelete("/{id}", GetAllTodosAsync)
         //    .Produces(StatusCodes.Status204NoContent)
@@ -61,14 +61,15 @@ public static async Task<Ok<TodoDto[]>> GetAllTodosAsync(IMediator mediator)
     /// <summary>
     /// Fetches a todo by Id
     /// </summary>
-    public static async Task<Results<BadRequest<ValidationErrorDto>, NotFound, Ok<TodoDto>>> GetTodoByIdAsync(Guid id, IMediator mediator)
+    public static async Task<Results<ValidationProblem, NotFound, Ok<TodoDto>>> GetTodoByIdAsync(Guid id, IMediator mediator)
     {
         if (id == Guid.Empty)
         {
-            return TypedResults.BadRequest<ValidationErrorDto>(
-                new(
-                    ValidationErrors: [new ValidationErrorItem("id", "id must not be an empty guid.")])
-                );
+            var errors = new Dictionary<string, string[]>
+            {
+                ["id"] = ["id parameter must not be an empty guid."],
+            };
+            return TypedResults.ValidationProblem(errors);
         }
 
         var todos = await mediator.Send(new GetAllTodosQuery());
@@ -97,17 +98,13 @@ public static async Task<Results<BadRequest<ValidationErrorDto>, NotFound, Ok<To
     /// </remarks>
     /// <response code="201">Returns the newly created item</response>
     /// <response code="400">Invalid payload</response>
-    public static async Task<Results<Created<TodoDto>, BadRequest>> CreateTodoAsync(TodoCreateDto input, IMediator mediator)
+    public static async Task<Results<Created<TodoDto>, ValidationProblem>> CreateTodoAsync(TodoCreateDto input, IMediator mediator)
     {
         var result = await mediator.Send(new CreateTodoCommand(input));
-        if (result.IsError && result.Exception is not null)
-        {
-            throw result.Exception;
-        }
 
-        if (result.HasValidationError && result.ValidationErrors.Any())
+        if (result.HasValidationError)
         {
-            return TypedResults.BadRequest();
+            return TypedResults.ValidationProblem(result.ValidationErrors.ToDictionary());
         }
 
         var todo = result.Value;

JixMinApiTests/Features/Todo/TodoEndpointsTests.cs

@@ -16,23 +16,24 @@ public async Task GetTodoByIdAsync_Returns_BadRequest_When_Id_Is_Empty()
         // Arrange
         var mediatorMock = new Mock<IMediator>();
         var emptyId = Guid.Empty;
-        var expectedBadRequest = new ValidationErrorDto(
-            [new ValidationErrorItem("id", "id must not be an empty guid.")]
-        );
+        var expectedErrors = new Dictionary<string, string[]>
+        {
+            ["id"] = ["id parameter must not be an empty guid."],
+        };
 
         // Act
         var response = await TodoEndpoints.GetTodoByIdAsync(emptyId, mediatorMock.Object);
 
         // Assert
-        Assert.IsType<Results<BadRequest<ValidationErrorDto>, NotFound, Ok<TodoDto>>>(response);
+        Assert.IsType<Results<ValidationProblem, NotFound, Ok<TodoDto>>>(response);
 
-        var result = (BadRequest<ValidationErrorDto>)response.Result;
+        var result = (ValidationProblem)response.Result;
         Assert.NotNull(result);
         Assert.Equal(StatusCodes.Status400BadRequest, result.StatusCode);
 
-        var value = Assert.IsType<ValidationErrorDto>(result.Value);
-        Assert.True(value.ValidationErrors.Any());
-        Assert.Equal(expectedBadRequest.ValidationErrors.FirstOrDefault(), value.ValidationErrors.FirstOrDefault());
+        var value = Assert.IsType<HttpValidationProblemDetails>(result.ProblemDetails);
+        Assert.True(value.Errors.Any());
+        Assert.Equal(expectedErrors.FirstOrDefault(), value.Errors.FirstOrDefault());
     }
 
     [Fact]
@@ -48,8 +49,8 @@ public async Task GetTodoByIdAsync_Returns_NotFound_When_Todo_Not_Found()
         var response = await TodoEndpoints.GetTodoByIdAsync(nonExistentId, mediatorMock.Object);
 
         // Assert
-        Assert.IsType<Results<BadRequest<ValidationErrorDto>, NotFound, Ok<TodoDto>>>(response);
-        
+        Assert.IsType<Results<ValidationProblem, NotFound, Ok<TodoDto>>>(response);
+
         var result = (NotFound)response.Result;
         Assert.NotNull(result);
         Assert.Equal(StatusCodes.Status404NotFound, result.StatusCode);
@@ -72,8 +73,8 @@ public async Task GetTodoByIdAsync_Returns_Ok_When_Todo_Found()
         var response = await TodoEndpoints.GetTodoByIdAsync(existingId, mediatorMock.Object);
 
         // Assert
-        Assert.IsType<Results<BadRequest<ValidationErrorDto>, NotFound, Ok<TodoDto>>>(response);
-        
+        Assert.IsType<Results<ValidationProblem, NotFound, Ok<TodoDto>>>(response);
+
         var result = (Ok<TodoDto>)response.Result;
         Assert.NotNull(result);
         Assert.Equal(StatusCodes.Status200OK, result.StatusCode);