[dotnet-watch] Simplify file watching

src/BuiltInTools/dotnet-watch/DotNetWatcher.cs

@@ -80,7 +80,9 @@ public override async Task WatchAsync(CancellationToken shutdownCancellationToke
 
                 using var currentRunCancellationSource = new CancellationTokenSource();
                 using var combinedCancellationSource = CancellationTokenSource.CreateLinkedTokenSource(shutdownCancellationToken, currentRunCancellationSource.Token);
-                using var fileSetWatcher = new FileWatcher(evaluationResult.Files, Context.Reporter);
+                using var fileSetWatcher = new FileWatcher(Context.Reporter);
+
+                fileSetWatcher.WatchContainingDirectories(evaluationResult.Files.Keys);
 
                 var processTask = ProcessRunner.RunAsync(processSpec, Context.Reporter, isUserApplication: true, launchResult: null, combinedCancellationSource.Token);
 
@@ -89,7 +91,7 @@ public override async Task WatchAsync(CancellationToken shutdownCancellationToke
 
                 while (true)
                 {
-                    fileSetTask = fileSetWatcher.GetChangedFileAsync(startedWatching: null, combinedCancellationSource.Token);
+                    fileSetTask = fileSetWatcher.WaitForFileChangeAsync(evaluationResult.Files, startedWatching: null, combinedCancellationSource.Token);
                     finishedTask = await Task.WhenAny(processTask, fileSetTask, cancelledTaskSource.Task);
 
                     if (staticFileHandler != null && finishedTask == fileSetTask && fileSetTask.Result.HasValue)
@@ -119,9 +121,11 @@ public override async Task WatchAsync(CancellationToken shutdownCancellationToke
                 {
                     // Process exited. Redo evalulation
                     buildEvaluator.RequiresRevaluation = true;
+
                     // Now wait for a file to change before restarting process
-                    changedFile = await fileSetWatcher.GetChangedFileAsync(
-                        () => Context.Reporter.Report(MessageDescriptor.WaitingForFileChangeBeforeRestarting),
+                    changedFile = await fileSetWatcher.WaitForFileChangeAsync(
+                        evaluationResult.Files,
+                        startedWatching: () => Context.Reporter.Report(MessageDescriptor.WaitingForFileChangeBeforeRestarting),
                         shutdownCancellationToken);
                 }
                 else

src/BuiltInTools/dotnet-watch/EnvironmentOptions.cs

@@ -34,7 +34,8 @@ internal sealed record EnvironmentOptions(
         bool SuppressLaunchBrowser = false,
         bool SuppressBrowserRefresh = false,
         bool SuppressEmojis = false,
-        TestFlags TestFlags = TestFlags.None)
+        TestFlags TestFlags = TestFlags.None,
+        string TestOutput = "")
     {
         public static EnvironmentOptions FromEnvironment() => new
         (
@@ -46,7 +47,8 @@ internal sealed record EnvironmentOptions(
             SuppressLaunchBrowser: EnvironmentVariables.SuppressLaunchBrowser,
             SuppressBrowserRefresh: EnvironmentVariables.SuppressBrowserRefresh,
             SuppressEmojis: EnvironmentVariables.SuppressEmojis,
-            TestFlags: EnvironmentVariables.TestFlags
+            TestFlags: EnvironmentVariables.TestFlags,
+            TestOutput: EnvironmentVariables.TestOutputDir
         );
 
         public bool RunningAsTest { get => (TestFlags & TestFlags.RunningAsTest) != TestFlags.None; }

src/BuiltInTools/dotnet-watch/EnvironmentVariables.cs

@@ -36,6 +36,7 @@ public static partial class Names
     public static bool SuppressBrowserRefresh => ReadBool("DOTNET_WATCH_SUPPRESS_BROWSER_REFRESH");
 
     public static TestFlags TestFlags => Environment.GetEnvironmentVariable("__DOTNET_WATCH_TEST_FLAGS") is { } value ? Enum.Parse<TestFlags>(value) : TestFlags.None;
+    public static string TestOutputDir => Environment.GetEnvironmentVariable("__DOTNET_WATCH_TEST_OUTPUT_DIR") ?? "";  
 
     public static string? AutoReloadWSHostName => Environment.GetEnvironmentVariable("DOTNET_WATCH_AUTO_RELOAD_WS_HOSTNAME");
     public static string? BrowserPath => Environment.GetEnvironmentVariable("DOTNET_WATCH_BROWSER_PATH");

src/BuiltInTools/dotnet-watch/Filters/BuildEvaluator.cs

@@ -84,8 +84,11 @@ private async ValueTask<EvaluationResult> CreateEvaluationResult(CancellationTok
                     return result;
                 }
 
-                context.Reporter.Warn("Fix the error to continue or press Ctrl+C to exit.");
-                await FileWatcher.WaitForFileChangeAsync(rootProjectFileSetFactory.RootProjectFile, context.Reporter, cancellationToken);
+                await FileWatcher.WaitForFileChangeAsync(
+                    rootProjectFileSetFactory.RootProjectFile,
+                    context.Reporter,
+                    startedWatching: () => context.Reporter.Warn("Fix the error to continue or press Ctrl+C to exit."),
+                    cancellationToken);
             }
         }
 

src/BuiltInTools/dotnet-watch/HotReload/DefaultDeltaApplier.cs

@@ -41,6 +41,11 @@ async Task<ImmutableArray<string>> ConnectAsync()
                     Reporter.Verbose($"Capabilities: '{capabilities}'");
                     return capabilities.Split(' ').ToImmutableArray();
                 }
+                catch (EndOfStreamException)
+                {
+                    // process terminated before capabilities sent:
+                    return [];
+                }
                 catch (Exception e) when (e is not OperationCanceledException)
                 {
                     // pipe might throw another exception when forcibly closed on process termination: