feature: Add a way to invoke a command specifying optional values by name (#1123)

* Add NamedArgumentTypeAttribute

* Add NamedArgumentTypeReader

* Fix superflous empty line.

* Fix logic for quoted arguments

* Throw an exception with a tailored message.

* Add a catch to wrap parsing/input errors

* Trim potential excess whitespace

* Fix an off-by-one

* Support to read an IEnumerable property

* Add a doc

* Add assertion for the collection test

test/Discord.Net.Tests/Discord.Net.Tests.csproj

@@ -3,6 +3,7 @@
     <OutputType>Exe</OutputType>
     <RootNamespace>Discord</RootNamespace>
     <TargetFramework>netcoreapp1.1</TargetFramework>
+    <DebugType>portable</DebugType>
     <PackageTargetFallback>$(PackageTargetFallback);portable-net45+win8+wp8+wpa81</PackageTargetFallback>
   </PropertyGroup>
   <ItemGroup>
@@ -23,8 +24,8 @@
     <PackageReference Include="Akavache" Version="5.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.7.2" />
     <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
-    <PackageReference Include="xunit" Version="2.3.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />
-    <PackageReference Include="xunit.runner.reporters" Version="2.3.1" />
+    <PackageReference Include="xunit" Version="2.4.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
+    <PackageReference Include="xunit.runner.reporters" Version="2.4.0" />
   </ItemGroup>
 </Project>

test/Discord.Net.Tests/Tests.TypeReaders.cs

@@ -0,0 +1,133 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Discord.Commands;
+using Xunit;
+
+namespace Discord
+{
+    public sealed class TypeReaderTests
+    {
+        [Fact]
+        public async Task TestNamedArgumentReader()
+        {
+            var commands = new CommandService();
+            var module = await commands.AddModuleAsync<TestModule>(null);
+
+            Assert.NotNull(module);
+            Assert.NotEmpty(module.Commands);
+
+            var cmd = module.Commands[0];
+            Assert.NotNull(cmd);
+            Assert.NotEmpty(cmd.Parameters);
+
+            var param = cmd.Parameters[0];
+            Assert.NotNull(param);
+            Assert.True(param.IsRemainder);
+
+            var result = await param.ParseAsync(null, "bar: hello foo: 42");
+            Assert.True(result.IsSuccess);
+
+            var m = result.BestMatch as ArgumentType;
+            Assert.NotNull(m);
+            Assert.Equal(expected: 42, actual: m.Foo);
+            Assert.Equal(expected: "hello", actual: m.Bar);
+        }
+
+        [Fact]
+        public async Task TestQuotedArgumentValue()
+        {
+            var commands = new CommandService();
+            var module = await commands.AddModuleAsync<TestModule>(null);
+
+            Assert.NotNull(module);
+            Assert.NotEmpty(module.Commands);
+
+            var cmd = module.Commands[0];
+            Assert.NotNull(cmd);
+            Assert.NotEmpty(cmd.Parameters);
+
+            var param = cmd.Parameters[0];
+            Assert.NotNull(param);
+            Assert.True(param.IsRemainder);
+
+            var result = await param.ParseAsync(null, "foo: 42 bar: 《hello》");
+            Assert.True(result.IsSuccess);
+
+            var m = result.BestMatch as ArgumentType;
+            Assert.NotNull(m);
+            Assert.Equal(expected: 42, actual: m.Foo);
+            Assert.Equal(expected: "hello", actual: m.Bar);
+        }
+
+        [Fact]
+        public async Task TestNonPatternInput()
+        {
+            var commands = new CommandService();
+            var module = await commands.AddModuleAsync<TestModule>(null);
+
+            Assert.NotNull(module);
+            Assert.NotEmpty(module.Commands);
+
+            var cmd = module.Commands[0];
+            Assert.NotNull(cmd);
+            Assert.NotEmpty(cmd.Parameters);
+
+            var param = cmd.Parameters[0];
+            Assert.NotNull(param);
+            Assert.True(param.IsRemainder);
+
+            var result = await param.ParseAsync(null, "foobar");
+            Assert.False(result.IsSuccess);
+            Assert.Equal(expected: CommandError.Exception, actual: result.Error);
+        }
+
+        [Fact]
+        public async Task TestMultiple()
+        {
+            var commands = new CommandService();
+            var module = await commands.AddModuleAsync<TestModule>(null);
+
+            Assert.NotNull(module);
+            Assert.NotEmpty(module.Commands);
+
+            var cmd = module.Commands[0];
+            Assert.NotNull(cmd);
+            Assert.NotEmpty(cmd.Parameters);
+
+            var param = cmd.Parameters[0];
+            Assert.NotNull(param);
+            Assert.True(param.IsRemainder);
+
+            var result = await param.ParseAsync(null, "manyints: \"1, 2, 3, 4, 5, 6, 7\"");
+            Assert.True(result.IsSuccess);
+
+            var m = result.BestMatch as ArgumentType;
+            Assert.NotNull(m);
+            Assert.Equal(expected: new int[] { 1, 2, 3, 4, 5, 6, 7 }, actual: m.ManyInts);
+        }
+    }
+
+    [NamedArgumentType]
+    public sealed class ArgumentType
+    {
+        public int Foo { get; set; }
+
+        [OverrideTypeReader(typeof(CustomTypeReader))]
+        public string Bar { get; set; }
+
+        public IEnumerable<int> ManyInts { get; set; }
+    }
+
+    public sealed class CustomTypeReader : TypeReader
+    {
+        public override Task<TypeReaderResult> ReadAsync(ICommandContext context, string input, IServiceProvider services)
+            => Task.FromResult(TypeReaderResult.FromSuccess(input));
+    }
+
+    public sealed class TestModule : ModuleBase
+    {
+        [Command("test")]
+        public Task TestCommand(ArgumentType arg) => Task.Delay(0);
+    }
+}