Ensure watched projects are not built in parallel to avoid file locking issues

src/Microsoft.Tye.Hosting/Model/Application.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Threading;
 
 namespace Microsoft.Tye.Hosting.Model
 {
@@ -17,6 +18,18 @@ namespace Microsoft.Tye.Hosting.Model
             Source = source.FullName;
             ContextDirectory = source.DirectoryName!;
             Services = services;
+
+            foreach (var s in Services.Values)
+            {
+                if (s.Description.RunInfo is ProjectRunInfo projectRunInfo)
+                {
+                    var projectFileName = projectRunInfo.ProjectFile.FullName;
+                    if (!ProjectFileLocks.ContainsKey(projectFileName))
+                    {
+                        ProjectFileLocks[projectFileName] = new SemaphoreSlim(1, 1);
+                    }
+                }
+            }
         }
 
         public string Source { get; }
@@ -25,6 +38,8 @@ namespace Microsoft.Tye.Hosting.Model
 
         public Dictionary<string, Service> Services { get; }
 
+        internal Dictionary<string, SemaphoreSlim> ProjectFileLocks { get; } = new Dictionary<string, SemaphoreSlim>();
+
         public Dictionary<object, object> Items { get; } = new Dictionary<object, object>();
 
         public string? Network { get; set; }

src/Microsoft.Tye.Hosting/ProcessRunner.cs

@@ -359,9 +359,24 @@ namespace Microsoft.Tye.Hosting
                             },
                             Build = async () =>
                             {
-                                if (service.Description.RunInfo is ProjectRunInfo)
+                                if (service.Description.RunInfo is ProjectRunInfo projectRunInfo)
                                 {
-                                    var buildResult = await ProcessUtil.RunAsync("dotnet", $"build \"{service.Status.ProjectFilePath}\" /nologo", throwOnError: false, workingDirectory: application.ContextDirectory);
+                                    ProcessResult buildResult;
+
+                                    var projectFile = projectRunInfo.ProjectFile.FullName;
+                                    var projectSemaphore = application.ProjectFileLocks[projectFile];
+                                    await projectSemaphore.WaitAsync();
+                                    try
+                                    {
+                                        _logger.LogDebug($"[{replica}] Building project {projectFile}:");
+                                        buildResult = await ProcessUtil.RunAsync("dotnet", $"build \"{service.Status.ProjectFilePath}\" /nologo", throwOnError: false, workingDirectory: application.ContextDirectory);
+                                    }
+                                    finally
+                                    {
+                                        _logger.LogDebug($"[{replica}] Finished Building project {projectFile}:");
+                                        projectSemaphore.Release();
+                                    }
+
                                     if (buildResult.ExitCode != 0)
                                     {
                                         _logger.LogInformation("Building projects failed with exit code {ExitCode}: \r\n" + buildResult.StandardOutput, buildResult.ExitCode);

src/Microsoft.Tye.Hosting/Watch/DotNetWatcher.cs

@@ -88,7 +88,7 @@ namespace Microsoft.DotNet.Watcher
                     if (finishedTask == processTask)
                     {
                         // Now wait for a file to change before restarting process
-                        await fileSetWatcher.GetChangedFileAsync(cancellationToken, () => _logger.LogWarning("Waiting for a file to change before restarting dotnet..."));
+                        await fileSetWatcher.GetChangedFileAsync(cancellationToken, () => _logger.LogWarning("watch: {Replica} Waiting for a file to change before restarting dotnet...", replica));
                     }
 
                     if (!string.IsNullOrEmpty(fileSetTask.Result))
@@ -112,7 +112,8 @@ namespace Microsoft.DotNet.Watcher
                                 // Build failed, keep retrying builds until successful build. 
                             }
 
-                            await fileSetWatcher.GetChangedFileAsync(cancellationToken, () => _logger.LogWarning("Waiting for a file to change before restarting dotnet..."));
+                            // Now wait for a file to change before restarting process
+                            await fileSetWatcher.GetChangedFileAsync(cancellationToken, () => _logger.LogWarning("watch: {Replica} Waiting for a file to change before restarting dotnet...", replica));
                         }
                     }
                 }