Write exception message correctly in case of CommandParseException. Fixes #114

Author: Matthiee

CommandLineParser.Tests/Exceptions/ExceptionsTest.cs

@@ -1,6 +1,9 @@
 using MatthiWare.CommandLine.Abstractions.Command;
 using MatthiWare.CommandLine.Core.Attributes;
 using MatthiWare.CommandLine.Core.Exceptions;
+using Moq;
+using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using Xunit;
@@ -130,6 +133,46 @@ public async Task CommandParseExceptionTestAsync()
             Assert.Same(parser.Commands.First(), result.Errors.Cast<CommandParseException>().First().Command);
         }
 
+        [Fact]
+        public void CommandParseException_Should_Contain_Correct_Message_Single()
+        {
+            var cmdMock = new Mock<ICommandLineCommand>();
+            cmdMock.SetupGet(_ => _.Name).Returns("test");
+
+            var exceptionList = new List<Exception>
+            {
+                new Exception("msg1")
+            };
+
+            var parseException = new CommandParseException(cmdMock.Object, exceptionList.AsReadOnly());
+            var msg = parseException.Message;
+            var expected = @"Unable to parse command 'test' because msg1";
+
+            Assert.Equal(expected, msg);
+        }
+
+        [Fact]
+        public void CommandParseException_Should_Contain_Correct_Message_Multiple()
+        {
+            var cmdMock = new Mock<ICommandLineCommand>();
+            cmdMock.SetupGet(_ => _.Name).Returns("test");
+
+            var exceptionList = new List<Exception>
+            {
+                new Exception("msg1"),
+                new Exception("msg2")
+            };
+
+            var parseException = new CommandParseException(cmdMock.Object, exceptionList.AsReadOnly());
+            var msg = parseException.Message;
+            var expected = @"Unable to parse command 'test' because 2 errors occured
+ - msg1
+ - msg2
+";
+
+            Assert.Equal(expected, msg);
+        }
+
         [Fact]
         public void OptionParseExceptionTest()
         {

CommandLineParser/Core/Exceptions/CommandParseException.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using System.Text;
 using MatthiWare.CommandLine.Abstractions.Command;
 
 namespace MatthiWare.CommandLine.Core.Exceptions
@@ -20,7 +22,36 @@ public class CommandParseException : BaseParserException
         /// <param name="command">the failed command</param>
         /// <param name="innerExceptions">collection of inner exception</param>
         public CommandParseException(ICommandLineCommand command, IReadOnlyCollection<Exception> innerExceptions)
-            : base(command, "", new AggregateException(innerExceptions))
+            : base(command, CreateMessage(command, innerExceptions), new AggregateException(innerExceptions))
         { }
+
+        private static string CreateMessage(ICommandLineCommand command, IReadOnlyCollection<Exception> exceptions)
+        {
+            if (exceptions.Count > 1)
+            {
+                return CreateMultipleExceptionsMessage(command, exceptions);
+            }
+            else
+            {
+                return CreateSingleExceptionMessage(command, exceptions.First());
+            }
+        }
+
+        private static string CreateSingleExceptionMessage(ICommandLineCommand command, Exception exception)
+            => $"Unable to parse command '{command.Name}' because {exception.Message}";
+
+
+        private static string CreateMultipleExceptionsMessage(ICommandLineCommand command, IReadOnlyCollection<Exception> exceptions)
+        {
+            var message = new StringBuilder();
+            message.AppendLine($"Unable to parse command '{command.Name}' because {exceptions.Count} errors occured");
+
+            foreach (var exception in exceptions)
+            {
+                message.AppendLine($" - {exception.Message}");
+            }
+
+            return message.ToString();
+        }
     }
 }