Release Candidate 0.2.0

src/Deveel.Results/IValidationError.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
+{
+    /// <summary>
+    /// Represents an error that occurred while validating a
+    /// a command or operation.
+    /// </summary>
+    public interface IValidationError : IOperationError
+    {
+        /// <summary>
+        /// Gets the list of validation results that caused the error.
+        /// </summary>
+        IReadOnlyList<ValidationResult> ValidationResults { get; }
+    }
+}

src/Deveel.Results/OperationResult.cs

@@ -1,4 +1,6 @@
-namespace Deveel
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
 {
     /// <summary>
     /// An operation result that has no value returned.
@@ -71,6 +73,26 @@ public static OperationResult Fail(IOperationError error)
         public static OperationResult Fail(string code, string domain, string? message = null, IOperationError? inner = null)
             => Fail(new OperationError(code, domain, message, inner));
 
+        /// <summary>
+        /// Creates a new instance of an operation result that has failed
+        /// because of a validation error.
+        /// </summary>
+        /// <param name="code">
+        /// The code of the error that has caused the operation to fail.
+        /// </param>
+        /// <param name="domain">
+        /// The domain where the error has occurred.
+        /// </param>
+        /// <param name="validationResults">
+        /// The list of validation results that have caused the operation to fail.
+        /// </param>
+        /// <returns>
+        /// Returns an instance of <see cref="OperationResult"/> that represents
+        /// a failed operation.
+        /// </returns>
+        public static OperationResult ValidationFailed(string code, string domain, IEnumerable<ValidationResult> validationResults)
+            => Fail(new OperationValidationError(code, domain, validationResults.ToList()));
+
         /// <summary>
         /// Implicitly converts an instance of an error to an operation result.
         /// </summary>

src/Deveel.Results/OperationResultExtensions.cs

@@ -1,23 +1,94 @@
-namespace Deveel
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
 {
     /// <summary>
     /// Extensions for the <see cref="IOperationResult"/> contract.
     /// </summary>
     public static class OperationResultExtensions
     {
+        /// <summary>
+        /// Determines if the operation result is a success.
+        /// </summary>
+        /// <param name="result">
+        /// The operation result to check.
+        /// </param>
+        /// <returns>
+        /// Returns <see langword="true"/> if the operation result is a success,
+        /// otherwise <see langword="false"/>.
+        /// </returns>
         public static bool IsSuccess(this IOperationResult result) 
             => result.ResultType == OperationResultType.Success;
 
+        /// <summary>
+        /// Determines if the operation result is an error.
+        /// </summary>
+        /// <param name="result">
+        /// The operation result to check.
+        /// </param>
+        /// <returns>
+        /// Returns <see langword="true"/> if the operation result is an error,
+        /// otherwise <see langword="false"/>.
+        /// </returns>
         public static bool IsError(this IOperationResult result)
             => result.ResultType == OperationResultType.Error;
 
+        /// <summary>
+        /// Determines if the operation result is cancelled.
+        /// </summary>
+        /// <param name="result">
+        /// The operation result to check.
+        /// </param>
+        /// <returns>
+        /// Returns <see langword="true"/> if the operation result is cancelled,
+        /// otherwise <see langword="false"/>.
+        /// </returns>
         public static bool IsCancelled(this IOperationResult result)
             => result.ResultType == OperationResultType.Cancelled;
 
+        /// <summary>
+        /// Determines if the operation has caused no changes
+        /// to the state of an object.
+        /// </summary>
+        /// <param name="result">
+        /// The operation result to check.
+        /// </param>
+        /// <returns>
+        /// Returns <see langword="true"/> if the operation has not
+        /// caused any changes to the object, otherwise <see langword="false"/>.
+        /// </returns>
         public static bool IsUnchanged(this IOperationResult result)
             => result.ResultType == OperationResultType.Unchanged;
 
+        /// <summary>
+        /// Checks if the operation result has validation errors.
+        /// </summary>
+        /// <param name="result">
+        /// The operation result to check.
+        /// </param>
+        /// <returns>
+        /// Returns <see langword="true"/> if the operation result is
+        /// an error and the type of the error is <see cref="IValidationError"/>,
+        /// otherwise <see langword="false"/>.
+        /// </returns>
+        public static bool HasValidationErrors(this IOperationResult result)
+            => result.IsError() && (result.Error is IValidationError);
+
+        /// <summary>
+        /// Gets the list of validation results that caused an operation
+        /// to fail.
+        /// </summary>
+        /// <param name="result">
+        /// The result that contains the validation errors.
+        /// </param>
+        /// <returns>
+        /// Returns a list of <see cref="ValidationResult"/> objects that
+        /// describe the validation errors that caused the operation to fail.
+        /// </returns>
+        public static IReadOnlyList<ValidationResult> ValidationResults(this IOperationResult result) 
+            => result.HasValidationErrors() ? ((IValidationError)result.Error!).ValidationResults : Array.Empty<ValidationResult>();
+
         public static TResult Match<TResult>(this IOperationResult result, 
             Func<TResult>? ifSuccess = null, 
             Func<IOperationError?, TResult>? ifError = null, 
             Func<TResult>? ifUnchanged = null)
@@ -45,7 +116,7 @@
             throw new InvalidOperationException("The operation result is in an unknown state.");
         }
 
         public static Task<TResult> MatchAsync<TResult>(this IOperationResult result,
             Func<Task<TResult>>? ifSuccess = null,
             Func<IOperationError?, Task<TResult>>? ifError = null,
             Func<Task<TResult>>? ifUnchanged = null)

src/Deveel.Results/OperationResult_T.cs

@@ -1,6 +1,8 @@
-namespace Deveel
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
 {
     public readonly struct OperationResult<T> : IOperationResult<T>
     {
         private OperationResult(OperationResultType resultType, T? value, IOperationError? error)
         {
@@ -42,24 +44,78 @@
             return new OperationResult<T>(OperationResultType.Success, value, null);
         }
 
+        /// <summary>
+        /// Creates a new instance of an operation result that has failed
+        /// because of an error.
+        /// </summary>
+        /// <param name="error">
+        /// The error that caused the operation to fail.
+        /// </param>
+        /// <returns>
+        /// Returns an instance of <see cref="OperationResult{T}"/> that
+        /// represents a failure in the operation.
+        /// </returns>
+        /// <exception cref="ArgumentNullException">
+        /// Thrown when the <paramref name="error"/> is <see langword="null"/>.
+        /// </exception>
         public static OperationResult<T> Fail(IOperationError error)
         {
             ArgumentNullException.ThrowIfNull(error, nameof(error));
             return new OperationResult<T>(OperationResultType.Error, default, error);
         }
 
+        /// <summary>
+        /// Creates a new instance of an operation result that has failed
+        /// because of an error.
+        /// </summary>
+        /// <param name="code">
+        /// The code of the error that caused the operation to fail.
+        /// </param>
+        /// <param name="domain">
+        /// The domain where the error occurred.
+        /// </param>
+        /// <param name="message">
+        /// A message that describes the error.
+        /// </param>
+        /// <param name="inner">
+        /// An inner error that caused the error.
+        /// </param>
+        /// <returns>
+        /// Returns an instance of <see cref="OperationResult{T}"/> that
+        /// represents a failure in the operation.
+        /// </returns>
         public static OperationResult<T> Fail(string code, string domain, string? message = null, IOperationError? inner = null)
         {
             ArgumentNullException.ThrowIfNull(code, nameof(code));
             ArgumentNullException.ThrowIfNull(domain, nameof(domain));
             return new OperationResult<T>(OperationResultType.Error, default, new OperationError(code, domain, message, inner));
         }
 
+        /// <summary>
+        /// Creates a new instance of an operation result that has failed
+        /// because of a validation error.
+        /// </summary>
+        /// <param name="code">
+        /// The code of the error that caused the operation to fail.
+        /// </param>
+        /// <param name="domain">
+        /// The domain where the error occurred.
+        /// </param>
+        /// <param name="results">
+        /// The list of validation results that caused the error.
+        /// </param>
+        /// <returns>
+        /// Returns an instance of <see cref="OperationResult{T}"/> that
+        /// represents a failure in the operation.
+        /// </returns>
+        public static OperationResult<T> ValidationFailed(string code, string domain, IEnumerable<ValidationResult> results)
+            => Fail(new OperationValidationError(code, domain, results.ToList()));
+
         public static implicit operator OperationResult<T>(OperationResult result)
             => new OperationResult<T>(result.ResultType, default, result.Error);
 
         public static implicit operator OperationResult<T>(T value) => Success(value);
 
         public static implicit operator OperationResult<T>(OperationException error) => Fail(error);
     }
 }

src/Deveel.Results/OperationValidationError.cs

@@ -0,0 +1,50 @@
+using System.ComponentModel.DataAnnotations;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Deveel
+{
+    /// <summary>
+    /// An error that occurred during the validation of an operation.
+    /// </summary>
+    public readonly struct OperationValidationError : IValidationError
+    {
+        /// <summary>
+        /// Constructs an instance of an <see cref="OperationValidationError"/> object.
+        /// </summary>
+        /// <param name="code">
+        /// The code of the error, that is unique within the
+        /// given domain.
+        /// </param>
+        /// <param name="domain">
+        /// The domain where the error occurred.
+        /// </param>
+        /// <param name="validationResults">
+        /// A list of validation results that caused the error.
+        /// </param>
+        public OperationValidationError(string code, string domain, IReadOnlyList<ValidationResult> validationResults)
+        {
+            ArgumentNullException.ThrowIfNull(code, nameof(code));
+            ArgumentNullException.ThrowIfNull(domain, nameof(domain));
+            ArgumentNullException.ThrowIfNull(validationResults, nameof(validationResults));
+
+            Code = code;
+            Domain = domain;
+            ValidationResults = validationResults;
+        }
+
+        /// <inheritdoc/>
+        public IReadOnlyList<ValidationResult> ValidationResults { get; }
+
+        /// <inheritdoc/>
+        public string Code { get; }
+
+        /// <inheritdoc/>
+        public string Domain { get; }
+
+        [ExcludeFromCodeCoverage]
+        string? IOperationError.Message => null;
+
+        [ExcludeFromCodeCoverage]
+        IOperationError? IOperationError.InnerError => null;
+    }
+}

test/Deveel.Results.XUnit/OperationErrorTests.cs

@@ -1,4 +1,6 @@
-namespace Deveel
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
 {
     public static class OperationErrorTests
     {
@@ -94,5 +96,20 @@ public static void OperationException_WithMessageAndInner()
             Assert.Equal("err.2", innerError.Code);
             Assert.Equal("biz", innerError.Domain);
         }
+
+        [Fact]
+        public static void ValidationError_WithResults()
+        {
+            var results = new[] {
+                new ValidationResult("First error of the validation", new []{ "Member1" }),
+                new ValidationResult("Second error of the validation", new []{"Member2"})
+            };
+
+            var error = new OperationValidationError("err.1", "biz", results);
+
+            Assert.Equal("err.1", error.Code);
+            Assert.Equal("biz", error.Domain);
+            Assert.Same(results, error.ValidationResults);
+        }
     }
 }

test/Deveel.Results.XUnit/OperationResultOfTTests.cs

@@ -1,4 +1,6 @@
-namespace Deveel
+using System.ComponentModel.DataAnnotations;
+
+namespace Deveel
 {
     public static class OperationResultOfTTests
     {
@@ -136,6 +138,25 @@ public static void ImplicitlyConvertFromOperationResult_Success()
 
         }
 
+        [Fact]
+        public static void OperationResult_FailForValidation()
+        {
+            var validations = new[] {
+                new ValidationResult("err.1", new []{ "Member1" }),
+                new ValidationResult("err.2", new []{ "Member2" })
+            };
+
+            var result = OperationResult<int>.ValidationFailed("err.1", "biz", validations);
+
+            Assert.Equal(OperationResultType.Error, result.ResultType);
+            Assert.NotNull(result.Error);
+            Assert.Equal("err.1", result.Error.Code);
+            Assert.Equal("biz", result.Error.Domain);
+            var opError = Assert.IsType<OperationValidationError>(result.Error);
+
+            Assert.Equal(validations.Length, opError.ValidationResults.Count);
+        }
+
         class DomainException : OperationException
         {
             public DomainException(string code)

test/Deveel.Results.XUnit/OperationResultTests.cs

@@ -1,5 +1,7 @@
 using Deveel;
 
+using System.ComponentModel.DataAnnotations;
+
 namespace Deveel;
 
 public static class OperationResultTests
@@ -184,4 +186,19 @@ public static void OperationResult_IsUnchanged()
         var result = OperationResult.NotChanged;
         Assert.True(result.IsUnchanged());
     }
+
+    [Fact]
+    public static void OperationResult_ValidationErrors()
+    {
+        var errors = new List<ValidationResult> {
+            new ValidationResult("The value is required", new[] { "value" }),
+            new ValidationResult("The value must be greater than 0", new[] { "value" })
+        };
+
+        var error = new OperationValidationError("err.1", "biz", errors);
+        var result = OperationResult.Fail(error);
+
+        Assert.True(result.HasValidationErrors());
+        Assert.Equal(errors, result.ValidationResults());
+    }
 }