Report workspace messages for warnings/errors from the build hosts

This connects our various error reporting systems so failures of the
build hosts can get passed along back to the existing reporting
mechanism for MSBuildWorkspace failures.

src/Workspaces/Core/MSBuild/MSBuild/DiagnosticReporterLoggerProvider.cs

@@ -0,0 +1,51 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.Contracts;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.CodeAnalysis.MSBuild;
+
+internal class DiagnosticReporterLoggerProvider : ILoggerProvider
+{
+    private readonly DiagnosticReporter _reporter;
+
+    public DiagnosticReporterLoggerProvider(DiagnosticReporter reporter)
+    {
+        _reporter = reporter;
+    }
+
+    public ILogger CreateLogger(string categoryName)
+    {
+        return new Logger(_reporter, categoryName);
+    }
+
+    public void Dispose()
+    {
+    }
+
+    private sealed class Logger(DiagnosticReporter reporter, string categoryName) : ILogger
+    {
+        public IDisposable? BeginScope<TState>(TState state) where TState : notnull
+        {
+            return null;
+        }
+
+        public bool IsEnabled(LogLevel logLevel)
+        {
+            return logLevel >= LogLevel.Warning;
+        }
+
+        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+        {
+            var kind = logLevel == LogLevel.Warning ? WorkspaceDiagnosticKind.Warning : WorkspaceDiagnosticKind.Failure;
+            var message = formatter(state, exception);
+            if (!string.IsNullOrEmpty(categoryName))
+                message = $"[{categoryName}] {message}";
+
+            reporter.Report(new WorkspaceDiagnostic(kind, message));
+        }
+    }
+}

src/Workspaces/Core/MSBuild/MSBuild/MSBuildProjectLoader.cs

@@ -9,7 +9,6 @@
 using System.Threading.Tasks;
 using Microsoft.Build.Framework;
 using Microsoft.CodeAnalysis.Host;
-using Microsoft.CodeAnalysis.MSBuild.Build;
 using Roslyn.Utilities;
 using MSB = Microsoft.Build;
 
@@ -24,6 +23,7 @@ public partial class MSBuildProjectLoader
         private readonly SolutionServices _solutionServices;
 
         private readonly DiagnosticReporter _diagnosticReporter;
+        private readonly Microsoft.Extensions.Logging.ILoggerFactory _loggerFactory;
         private readonly PathResolver _pathResolver;
         private readonly ProjectFileExtensionRegistry _projectFileExtensionRegistry;
 
@@ -33,11 +33,13 @@ public partial class MSBuildProjectLoader
         internal MSBuildProjectLoader(
             SolutionServices solutionServices,
             DiagnosticReporter diagnosticReporter,
+            Microsoft.Extensions.Logging.ILoggerFactory loggerFactory,
             ProjectFileExtensionRegistry? projectFileExtensionRegistry,
             ImmutableDictionary<string, string>? properties)
         {
             _solutionServices = solutionServices;
             _diagnosticReporter = diagnosticReporter;
+            _loggerFactory = loggerFactory;
             _pathResolver = new PathResolver(_diagnosticReporter);
             _projectFileExtensionRegistry = projectFileExtensionRegistry ?? new ProjectFileExtensionRegistry(solutionServices, _diagnosticReporter);
 
@@ -188,7 +190,7 @@ public async Task<SolutionInfo> LoadSolutionInfoAsync(
                 }
             }
 
-            var buildHostProcessManager = new BuildHostProcessManager(Properties);
+            var buildHostProcessManager = new BuildHostProcessManager(Properties, loggerFactory: _loggerFactory);
             await using var _ = buildHostProcessManager.ConfigureAwait(false);
 
             var worker = new Worker(
@@ -250,7 +252,7 @@ public async Task<ImmutableArray<ProjectInfo>> LoadProjectInfoAsync(
                 onPathFailure: reportingMode,
                 onLoaderFailure: reportingMode);
 
-            var buildHostProcessManager = new BuildHostProcessManager(Properties);
+            var buildHostProcessManager = new BuildHostProcessManager(Properties, loggerFactory: _loggerFactory);
             await using var _ = buildHostProcessManager.ConfigureAwait(false);
 
             var worker = new Worker(

src/Workspaces/Core/MSBuild/MSBuild/MSBuildWorkspace.cs

@@ -31,6 +31,7 @@ public sealed class MSBuildWorkspace : Workspace
         private readonly NonReentrantLock _serializationLock = new();
 
         private readonly MSBuildProjectLoader _loader;
+        private readonly Microsoft.Extensions.Logging.ILoggerFactory _loggerFactory;
         private readonly ProjectFileExtensionRegistry _projectFileExtensionRegistry;
         private readonly DiagnosticReporter _reporter;
 
@@ -41,7 +42,9 @@ private MSBuildWorkspace(
         {
             _reporter = new DiagnosticReporter(this);
             _projectFileExtensionRegistry = new ProjectFileExtensionRegistry(Services.SolutionServices, _reporter);
-            _loader = new MSBuildProjectLoader(Services.SolutionServices, _reporter, _projectFileExtensionRegistry, properties);
+            _loggerFactory = new Microsoft.Extensions.Logging.LoggerFactory([new DiagnosticReporterLoggerProvider(_reporter)],
+                new Microsoft.Extensions.Logging.LoggerFilterOptions() { MinLevel = Microsoft.Extensions.Logging.LogLevel.Warning });
+            _loader = new MSBuildProjectLoader(Services.SolutionServices, _reporter, _loggerFactory, _projectFileExtensionRegistry, properties);
         }
 
         /// <summary>
@@ -312,7 +315,7 @@ internal override bool TryApplyChanges(Solution newSolution, IProgress<CodeAnaly
                 try
                 {
                     Debug.Assert(_applyChangesBuildHostProcessManager == null);
-                    _applyChangesBuildHostProcessManager = new BuildHostProcessManager(Properties);
+                    _applyChangesBuildHostProcessManager = new BuildHostProcessManager(Properties, loggerFactory: _loggerFactory);
 
                     return base.TryApplyChanges(newSolution, progressTracker);
                 }