Console.Write() doesn't show output until a newline

When running an app with `dotnet run`, we are redirecting the standard out and error just to print it out to our standard out and error. However, we are batching the output until we hit a newline, which isn't ideal for console apps.

To fix this, `dotnet run` no longer redirects the standard out and error.

Fix #2777

Microsoft.DotNet.Cli.sln

@@ -111,6 +111,8 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Performance", "test\Perform
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "binding-redirects.Tests", "test\binding-redirects.Tests\binding-redirects.Tests.xproj", "{27DBF851-F2E3-4FD5-BF4D-A73C81933283}"
 EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "dotnet-run.UnitTests", "test\dotnet-run.UnitTests\dotnet-run.UnitTests.xproj", "{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -795,6 +797,22 @@ Global
 		{27DBF851-F2E3-4FD5-BF4D-A73C81933283}.RelWithDebInfo|Any CPU.Build.0 = Release|Any CPU
 		{27DBF851-F2E3-4FD5-BF4D-A73C81933283}.RelWithDebInfo|x64.ActiveCfg = Release|Any CPU
 		{27DBF851-F2E3-4FD5-BF4D-A73C81933283}.RelWithDebInfo|x64.Build.0 = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Debug|x64.Build.0 = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.MinSizeRel|Any CPU.ActiveCfg = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.MinSizeRel|Any CPU.Build.0 = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.MinSizeRel|x64.ActiveCfg = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.MinSizeRel|x64.Build.0 = Debug|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Release|x64.ActiveCfg = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.Release|x64.Build.0 = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.RelWithDebInfo|Any CPU.ActiveCfg = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.RelWithDebInfo|Any CPU.Build.0 = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.RelWithDebInfo|x64.ActiveCfg = Release|Any CPU
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D}.RelWithDebInfo|x64.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -847,5 +865,6 @@ Global
 		{35E3C2DC-9B38-4EC5-8DD7-C32458DC485F} = {17735A9D-BFD9-4585-A7CB-3208CA6EA8A7}
 		{6A3095FF-A7C5-4300-85A9-C025C384401D} = {17735A9D-BFD9-4585-A7CB-3208CA6EA8A7}
 		{27DBF851-F2E3-4FD5-BF4D-A73C81933283} = {17735A9D-BFD9-4585-A7CB-3208CA6EA8A7}
+		{2A5EEC38-3030-44EF-9E58-6771E7BAB01D} = {17735A9D-BFD9-4585-A7CB-3208CA6EA8A7}
 	EndGlobalSection
 EndGlobal

scripts/dotnet-cli-build/TestTargets.cs

@@ -31,6 +31,7 @@ namespace Microsoft.DotNet.Cli.Build
             "dotnet-publish.Tests",
             "dotnet-resgen.Tests",
             "dotnet-run.Tests",
+            "dotnet-run.UnitTests",
             "dotnet-test.Tests",
             "dotnet-test.UnitTests",
             "Kestrel.Tests",

src/Microsoft.DotNet.Cli.Utils/Command.cs

@@ -16,8 +16,8 @@ namespace Microsoft.DotNet.Cli.Utils
     public class Command : ICommand
     {
         private readonly Process _process;
-        private readonly StreamForwarder _stdOut;
+        private StreamForwarder _stdOut;
-        private readonly StreamForwarder _stdErr;
+        private StreamForwarder _stdErr;
 
         private bool _running = false;
 
@@ -27,14 +27,9 @@ namespace Microsoft.DotNet.Cli.Utils
             {
                 FileName = commandSpec.Path,
                 Arguments = commandSpec.Args,
-                RedirectStandardError = true,
-                RedirectStandardOutput = true,
                 UseShellExecute = false
             };
 
-            _stdOut = new StreamForwarder();
-            _stdErr = new StreamForwarder();
-
             _process = new Process
             {
                 StartInfo = psi
@@ -134,11 +129,12 @@ namespace Microsoft.DotNet.Cli.Utils
 
                 Reporter.Verbose.WriteLine($"Process ID: {_process.Id}");
 
-                var taskOut = _stdOut.BeginRead(_process.StandardOutput);
+                var taskOut = _stdOut?.BeginRead(_process.StandardOutput);
-                var taskErr = _stdErr.BeginRead(_process.StandardError);
+                var taskErr = _stdErr?.BeginRead(_process.StandardError);
                 _process.WaitForExit();
 
-                Task.WaitAll(taskOut, taskErr);
+                taskOut?.Wait();
+                taskErr?.Wait();
             }
 
             var exitCode = _process.ExitCode;
@@ -158,8 +154,8 @@ namespace Microsoft.DotNet.Cli.Utils
             return new CommandResult(
                 this._process.StartInfo,
                 exitCode,
-                _stdOut.CapturedOutput,
+                _stdOut?.CapturedOutput,
-                _stdErr.CapturedOutput);
+                _stdErr?.CapturedOutput);
         }
 
         public ICommand WorkingDirectory(string projectDirectory)
@@ -181,6 +177,7 @@ namespace Microsoft.DotNet.Cli.Utils
         public ICommand CaptureStdOut()
         {
             ThrowIfRunning();
+            EnsureStdOut();
             _stdOut.Capture();
             return this;
         }
@@ -188,6 +185,7 @@ namespace Microsoft.DotNet.Cli.Utils
         public ICommand CaptureStdErr()
         {
             ThrowIfRunning();
+            EnsureStdErr();
             _stdErr.Capture();
             return this;
         }
@@ -197,6 +195,8 @@ namespace Microsoft.DotNet.Cli.Utils
             ThrowIfRunning();
             if (!onlyIfVerbose || CommandContext.IsVerbose())
             {
+                EnsureStdOut();
+
                 if (to == null)
                 {
                     _stdOut.ForwardTo(writeLine: Reporter.Output.WriteLine);
@@ -215,6 +215,8 @@ namespace Microsoft.DotNet.Cli.Utils
             ThrowIfRunning();
             if (!onlyIfVerbose || CommandContext.IsVerbose())
             {
+                EnsureStdErr();
+
                 if (to == null)
                 {
                     _stdErr.ForwardTo(writeLine: Reporter.Error.WriteLine);
@@ -231,6 +233,8 @@ namespace Microsoft.DotNet.Cli.Utils
         public ICommand OnOutputLine(Action<string> handler)
         {
             ThrowIfRunning();
+            EnsureStdOut();
+
             _stdOut.ForwardTo(writeLine: handler);
             return this;
         }
@@ -238,6 +242,8 @@ namespace Microsoft.DotNet.Cli.Utils
         public ICommand OnErrorLine(Action<string> handler)
         {
             ThrowIfRunning();
+            EnsureStdErr();
+
             _stdErr.ForwardTo(writeLine: handler);
             return this;
         }
@@ -258,6 +264,18 @@ namespace Microsoft.DotNet.Cli.Utils
             return info.FileName + " " + info.Arguments;
         }
 
+        private void EnsureStdOut()
+        {
+            _stdOut = _stdOut ?? new StreamForwarder();
+            _process.StartInfo.RedirectStandardOutput = true;
+        }
+
+        private void EnsureStdErr()
+        {
+            _stdErr = _stdErr ?? new StreamForwarder();
+            _process.StartInfo.RedirectStandardError = true;
+        }
+
         private void ThrowIfRunning([CallerMemberName] string memberName = null)
         {
             if (_running)

src/dotnet/commands/dotnet-run/RunCommand.cs

@@ -20,16 +20,26 @@ namespace Microsoft.DotNet.Tools.Run
         public string Project = null;
         public IReadOnlyList<string> Args = null;
 
+        private readonly ICommandFactory _commandFactory;
+        private ProjectContext _context;
+        private List<string> _args;
+        private BuildWorkspace _workspace;
+
         public static readonly string[] DefaultFrameworks = new[]
         {
             FrameworkConstants.FrameworkIdentifiers.NetCoreApp,
             FrameworkConstants.FrameworkIdentifiers.NetStandardApp,
         };
 
+        public RunCommand()
+            : this(new RunCommandFactory())
+        {
+        }
 
-        ProjectContext _context;
+        public RunCommand(ICommandFactory commandFactory)
-        List<string> _args;
+        {
-        private BuildWorkspace _workspace;
+            _commandFactory = commandFactory;
+        }
 
         public int Start()
         {
@@ -166,24 +176,22 @@ namespace Microsoft.DotNet.Tools.Run
                 }
             }
 
-            Command command;
+            ICommand command;
             if (outputName.EndsWith(FileNameSuffixes.DotNet.DynamicLib, StringComparison.OrdinalIgnoreCase))
             {
                 // The executable is a ".dll", we need to call it through dotnet.exe
                 var muxer = new Muxer();
 
-                command = Command.Create(muxer.MuxerPath, Enumerable.Concat(
+                command = _commandFactory.Create(muxer.MuxerPath, Enumerable.Concat(
                             Enumerable.Concat(new string[] { "exec" }, hostArgs),
                             Enumerable.Concat(new string[] { outputName }, _args)));
             }
             else
             {
-                command = Command.Create(outputName, Enumerable.Concat(hostArgs, _args));
+                command = _commandFactory.Create(outputName, Enumerable.Concat(hostArgs, _args));
             }
 
             result = command
-                .ForwardStdOut()
-                .ForwardStdErr()
                 .Execute()
                 .ExitCode;
 
@@ -198,5 +206,13 @@ namespace Microsoft.DotNet.Tools.Run
             var result = command.Execute();
             return result.ExitCode;
         }
+
+        private class RunCommandFactory : ICommandFactory
+        {
+            public ICommand Create(string commandName, IEnumerable<string> args, NuGetFramework framework = null, string configuration = "Debug")
+            {
+                return Command.Create(commandName, args, framework, configuration);
+            }
+        }
     }
 }

test/dotnet-run.UnitTests/GivenARunCommand.cs

@@ -0,0 +1,122 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using FluentAssertions;
+using Microsoft.DotNet.Cli.Utils;
+using Microsoft.DotNet.TestFramework;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using NuGet.Frameworks;
+using Xunit;
+
+namespace Microsoft.DotNet.Tools.Run.Tests
+{
+    public class GivenARunCommand : TestBase
+    {
+        private const int RunExitCode = 29;
+
+        [Fact]
+        public void ItDoesntRedirectStandardOutAndError()
+        {
+            TestInstance instance = TestAssetsManager.CreateTestInstance("TestAppSimple")
+                                         .WithLockFiles();
+
+            new BuildCommand(instance.TestRoot)
+                .Execute()
+                .Should()
+                .Pass();
+
+            RunCommand runCommand = new RunCommand(new FailOnRedirectOutputCommandFactory());
+            runCommand.Project = instance.TestRoot;
+
+            runCommand.Start()
+                .Should()
+                .Be(RunExitCode);
+        }
+
+        private class FailOnRedirectOutputCommandFactory : ICommandFactory
+        {
+            public ICommand Create(string commandName, IEnumerable<string> args, NuGetFramework framework = null, string configuration = "Debug")
+            {
+                return new FailOnRedirectOutputCommand();
+            }
+
+            /// <summary>
+            /// A Command that will fail if a caller tries redirecting StdOut or StdErr.
+            /// </summary>
+            private class FailOnRedirectOutputCommand : ICommand
+            {
+                public CommandResult Execute()
+                {
+                    return new CommandResult(null, RunExitCode, null, null);
+                }
+
+                public ICommand CaptureStdErr()
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand CaptureStdOut()
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand ForwardStdErr(TextWriter to = null, bool onlyIfVerbose = false, bool ansiPassThrough = true)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand ForwardStdOut(TextWriter to = null, bool onlyIfVerbose = false, bool ansiPassThrough = true)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand OnErrorLine(Action<string> handler)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public ICommand OnOutputLine(Action<string> handler)
+                {
+                    throw new NotSupportedException();
+                }
+
+                public string CommandArgs
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public string CommandName
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public CommandResolutionStrategy ResolutionStrategy
+                {
+                    get
+                    {
+                        throw new NotImplementedException();
+                    }
+                }
+
+                public ICommand EnvironmentVariable(string name, string value)
+                {
+                    throw new NotImplementedException();
+                }
+
+                public ICommand WorkingDirectory(string projectDirectory)
+                {
+                    throw new NotImplementedException();
+                }
+            }
+        }
+    }
+}

test/dotnet-run.UnitTests/dotnet-run.UnitTests.xproj

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0.24720" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0.24720</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>2a5eec38-3030-44ef-9e58-6771e7bab01d</ProjectGuid>
+    <RootNamespace>Microsoft.DotNet.Tools.Run.UnitTests</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

test/dotnet-run.UnitTests/project.json

@@ -0,0 +1,27 @@
+{
+  "version": "1.0.0-*",
+  "dependencies": {
+    "Microsoft.NETCore.App": {
+      "type": "platform",
+      "version": "1.0.0-rc3-*"
+    },
+    "System.Runtime.Serialization.Primitives": "4.1.1-rc2-24027",
+    "dotnet": {
+      "target": "project"
+    },
+    "Microsoft.DotNet.Tools.Tests.Utilities": {
+      "target": "project"
+    },
+    "xunit": "2.1.0",
+    "dotnet-test-xunit": "1.0.0-rc2-173361-36"
+  },
+  "frameworks": {
+    "netcoreapp1.0": {
+      "imports": [
+        "dotnet5.4",
+        "portable-net451+win8"
+      ]
+    }
+  },
+  "testRunner": "xunit"
+}