Add --msbuildprojectextensionspath option to dotnet-watch

In the event someone wants to move the obj/ folder, MSBuild will not be able to locate dotnet-watch's generated targets. dotnet-watch cannot automatically find the obj folder (#244), so this command line switch allows users to point dotnet-watch to the right location.

src/Microsoft.DotNet.Watcher.Tools/CommandLineOptions.cs

@@ -12,6 +12,7 @@ namespace Microsoft.DotNet.Watcher
     internal class CommandLineOptions
     {
         public string Project { get; private set; }
+        public string MSBuildProjectExtensionsPath { get; private set; }
         public bool IsHelp { get; private set; }
         public bool IsQuiet { get; private set; }
         public bool IsVerbose { get; private set; }
@@ -61,8 +62,16 @@ Examples:
             };
 
             app.HelpOption("-?|-h|--help");
-            var optProjects = app.Option("-p|--project", "The project to watch",
+            // TODO multiple shouldn't be too hard to support
-                CommandOptionType.SingleValue); // TODO multiple shouldn't be too hard to support
+            var optProjects = app.Option("-p|--project <PROJECT>", "The project to watch",
+                CommandOptionType.SingleValue);
+
+            var optMSBuildProjectExtensionsPath = app.Option("--msbuildprojectextensionspath <PATH>",
+                "The MSBuild project extensions path. Defaults to \"obj\".",
+                CommandOptionType.SingleValue);
+            // Hide from help text because this is an internal option that will hopefully go away when/if #244 is resolved.
+            optMSBuildProjectExtensionsPath.ShowInHelpText = false;
+
             var optQuiet = app.Option("-q|--quiet", "Suppresses all output except warnings and errors",
                 CommandOptionType.NoValue);
             var optVerbose = app.VerboseOption();
@@ -92,6 +101,7 @@ Examples:
             return new CommandLineOptions
             {
                 Project = optProjects.Value(),
+                MSBuildProjectExtensionsPath = optMSBuildProjectExtensionsPath.Value(),
                 IsQuiet = optQuiet.HasValue(),
                 IsVerbose = optVerbose.HasValue(),
                 RemainingArguments = app.RemainingArguments,

src/Microsoft.DotNet.Watcher.Tools/Internal/MsBuildFileSetFactory.cs

@@ -21,19 +21,26 @@ namespace Microsoft.DotNet.Watcher.Internal
         private const string WatchTargetsFileName = "DotNetWatchCommon.targets";
         private readonly IReporter _reporter;
         private readonly string _projectFile;
+        private readonly string _projectExtensionsPath;
         private readonly string _watchTargetsDir;
         private readonly OutputSink _outputSink;
         private readonly ProcessRunner _processRunner;
         private readonly bool _waitOnError;
 
-        public MsBuildFileSetFactory(IReporter reporter, string projectFile, bool waitOnError)
+        public MsBuildFileSetFactory(IReporter reporter,
-            : this(reporter, projectFile, new OutputSink())
+            string projectFile,
+            string msBuildProjectExtensionsPath,
+            bool waitOnError)
+            : this(reporter, projectFile, msBuildProjectExtensionsPath, new OutputSink())
         {
             _waitOnError = waitOnError;
         }
 
         // output sink is for testing
-        internal MsBuildFileSetFactory(IReporter reporter, string projectFile, OutputSink outputSink)
+        internal MsBuildFileSetFactory(IReporter reporter,
+            string projectFile,
+            string msBuildProjectExtensionsPath,
+            OutputSink outputSink)
         {
             Ensure.NotNull(reporter, nameof(reporter));
             Ensure.NotNullOrEmpty(projectFile, nameof(projectFile));
@@ -44,6 +51,11 @@ namespace Microsoft.DotNet.Watcher.Internal
             _watchTargetsDir = FindWatchTargetsDir();
             _outputSink = outputSink;
             _processRunner = new ProcessRunner(reporter);
+
+            // default value for MSBuildProjectExtensionsPath is $(BaseIntermediateOutputPath), which defaults to 'obj/'.
+            _projectExtensionsPath = string.IsNullOrEmpty(msBuildProjectExtensionsPath)
+                ? Path.Combine(Path.GetDirectoryName(_projectFile), "obj")
+                : msBuildProjectExtensionsPath;
         }
 
         internal List<string> BuildFlags { get; } = new List<string>
@@ -153,11 +165,8 @@ namespace Microsoft.DotNet.Watcher.Internal
         // Ensures file exists in $(MSBuildProjectExtensionsPath)/$(MSBuildProjectFile).dotnetwatch.targets
         private void EnsureInitialized()
         {
-            // default value for MSBuildProjectExtensionsPath.
-            var projectExtensionsPath = Path.Combine(Path.GetDirectoryName(_projectFile), "obj");
-
             // see https://github.com/Microsoft/msbuild/blob/bf9b21cc7869b96ea2289ff31f6aaa5e1d525a26/src/XMakeTasks/Microsoft.Common.targets#L127
-            var projectExtensionFile = Path.Combine(projectExtensionsPath,
+            var projectExtensionFile = Path.Combine(_projectExtensionsPath,
                 Path.GetFileName(_projectFile) + ProjectExtensionFileExtension);
 
             if (!File.Exists(projectExtensionFile))

src/Microsoft.DotNet.Watcher.Tools/Program.cs

@@ -81,12 +81,14 @@ namespace Microsoft.DotNet.Watcher
                 {
                     return await ListFilesAsync(_reporter,
                         options.Project,
+                        options.MSBuildProjectExtensionsPath,
                         _cts.Token);
                 }
                 else
                 {
                     return await MainInternalAsync(_reporter,
                         options.Project,
+                        options.MSBuildProjectExtensionsPath,
                         options.RemainingArguments,
                         _cts.Token);
                 }
@@ -121,6 +123,7 @@ namespace Microsoft.DotNet.Watcher
         private async Task<int> MainInternalAsync(
             IReporter reporter,
             string project,
+            string msbuildProjectExtensionsPath,
             ICollection<string> args,
             CancellationToken cancellationToken)
         {
@@ -136,7 +139,10 @@ namespace Microsoft.DotNet.Watcher
                 return 1;
             }
 
-            var fileSetFactory = new MsBuildFileSetFactory(reporter, projectFile, waitOnError: true);
+            var fileSetFactory = new MsBuildFileSetFactory(reporter,
+                projectFile,
+                NormalizePath(msbuildProjectExtensionsPath),
+                waitOnError: true);
             var processInfo = new ProcessSpec
             {
                 Executable = DotNetMuxer.MuxerPathOrDefault(),
@@ -157,6 +163,7 @@ namespace Microsoft.DotNet.Watcher
         private async Task<int> ListFilesAsync(
             IReporter reporter,
             string project,
+            string msbuildProjectExtensionsPath,
             CancellationToken cancellationToken)
         {
             // TODO multiple projects should be easy enough to add here
@@ -171,7 +178,10 @@ namespace Microsoft.DotNet.Watcher
                 return 1;
             }
 
-            var fileSetFactory = new MsBuildFileSetFactory(reporter, projectFile, waitOnError: false);
+            var fileSetFactory = new MsBuildFileSetFactory(reporter,
+                projectFile,
+                NormalizePath(msbuildProjectExtensionsPath),
+                waitOnError: false);
             var files = await fileSetFactory.CreateAsync(cancellationToken);
 
             if (files == null)
@@ -190,6 +200,22 @@ namespace Microsoft.DotNet.Watcher
         private static IReporter CreateReporter(bool verbose, bool quiet, IConsole console)
             => new PrefixConsoleReporter(console, verbose || CliContext.IsGlobalVerbose(), quiet);
 
+
+        private string NormalizePath(string path)
+        {
+            if (path == null || Path.IsPathRooted(path))
+            {
+                return path;
+            }
+
+            if (string.IsNullOrWhiteSpace(path))
+            {
+                return _workingDir;
+            }
+
+            return Path.Combine(_workingDir, path);
+        }
+
         public void Dispose()
         {
             _console.CancelKeyPress -= OnCancelKeyPress;

test/Microsoft.DotNet.Watcher.Tools.FunctionalTests/DotNetWatcherTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Xunit;
 using Xunit.Abstractions;
@@ -40,6 +41,11 @@ namespace Microsoft.DotNet.Watcher.Tools.FunctionalTests
                 : base("KitchenSink", logger)
             {
             }
+
+            protected override IEnumerable<string> GetDefaultArgs()
+            {
+                return new[] { "--msbuildprojectextensionspath", ".net/obj", "run", "--" };
+            }
         }
     }
 }

test/Microsoft.DotNet.Watcher.Tools.FunctionalTests/Scenario/WatchableApp.cs

@@ -96,7 +96,7 @@ namespace Microsoft.DotNet.Watcher.Tools.FunctionalTests
                 await PrepareAsync();
             }
 
-            var args = new[] { "run", "--" }.Concat(arguments);
+            var args = GetDefaultArgs().Concat(arguments);
             Start(args, name);
 
             // Make this timeout long because it depends much on the MSBuild compilation speed.
@@ -104,6 +104,11 @@ namespace Microsoft.DotNet.Watcher.Tools.FunctionalTests
             await Process.GetOutputLineAsync(StartedMessage).TimeoutAfter(TimeSpan.FromMinutes(2));
         }
 
+        protected virtual IEnumerable<string> GetDefaultArgs()
+        {
+            return new[] { "run", "--" };
+        }
+
         public virtual void Dispose()
         {
             _logger?.WriteLine("Disposing WatchableApp");

test/Microsoft.DotNet.Watcher.Tools.FunctionalTests/TestProjects/KitchenSink/KitchenSink.csproj

@@ -1,8 +1,16 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project>
+
+  <PropertyGroup>
+    <BaseIntermediateOutputPath>.net/obj</BaseIntermediateOutputPath>
+  </PropertyGroup>
+
+  <Import Project="Sdk.props" Sdk="Microsoft.NET.Sdk" />
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.0</TargetFramework>
   </PropertyGroup>
 
+  <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />
+
 </Project>

test/Microsoft.DotNet.Watcher.Tools.Tests/MsBuildFileSetFactoryTest.cs

@@ -238,7 +238,7 @@ namespace Microsoft.DotNet.Watcher.Tools.Tests
             graph.Find("A").WithProjectReference(graph.Find("W"), watch: false);
 
             var output = new OutputSink();
-            var filesetFactory = new MsBuildFileSetFactory(_reporter, graph.GetOrCreate("A").Path, output)
+            var filesetFactory = new MsBuildFileSetFactory(_reporter, graph.GetOrCreate("A").Path, null, output)
             {
                 // enables capturing markers to know which projects have been visited
                 BuildFlags = { "/p:_DotNetWatchTraceOutput=true" }
@@ -280,7 +280,7 @@ namespace Microsoft.DotNet.Watcher.Tools.Tests
         }
 
         private Task<IFileSet> GetFileSet(TemporaryCSharpProject target)
-            => GetFileSet(new MsBuildFileSetFactory(_reporter, target.Path, waitOnError: false));
+            => GetFileSet(new MsBuildFileSetFactory(_reporter, target.Path, null, waitOnError: false));
 
         private async Task<IFileSet> GetFileSet(MsBuildFileSetFactory filesetFactory)
         {