Fix swallowed watcher exceptions, deduplicate IsHiddenResource, reduce per-line allocations

- ResourceSnapshotWatcher: store post-initial-load exceptions in WatchException
  instead of silently dropping them
- Remove duplicate IsHiddenResource from AppHostAuxiliaryBackchannel and
  TestAppHostAuxiliaryBackchannel; use ResourceSnapshotMapper.IsHiddenResource
- LogsCommand.CollectLogsAsync: snapshot resource list once for non-follow path
  instead of re-enumerating ConcurrentDictionary per log line

Author: JamesNK

src/Aspire.Cli/Backchannel/AppHostAuxiliaryBackchannel.cs

@@ -271,7 +271,7 @@ public async Task<List<ResourceSnapshot>> GetResourceSnapshotsAsync(bool include
 
             if (!includeHidden)
             {
-                snapshots = snapshots.Where(s => !IsHiddenResource(s)).ToList();
+                snapshots = snapshots.Where(s => !ResourceSnapshotMapper.IsHiddenResource(s)).ToList();
             }
 
             // Sort resources by name for consistent ordering.
@@ -312,7 +312,7 @@ public async IAsyncEnumerable<ResourceSnapshot> WatchResourceSnapshotsAsync(bool
 
         await foreach (var snapshot in snapshots.WithCancellation(cancellationToken).ConfigureAwait(false))
         {
-            if (!includeHidden && IsHiddenResource(snapshot))
+            if (!includeHidden && ResourceSnapshotMapper.IsHiddenResource(snapshot))
             {
                 continue;
             }
@@ -321,11 +321,6 @@ public async IAsyncEnumerable<ResourceSnapshot> WatchResourceSnapshotsAsync(bool
         }
     }
 
-    private static bool IsHiddenResource(ResourceSnapshot snapshot)
-    {
-        return snapshot.IsHidden || string.Equals(snapshot.State, "Hidden", StringComparison.OrdinalIgnoreCase);
-    }
-
     /// <inheritdoc />
     public async IAsyncEnumerable<ResourceLogLine> GetResourceLogsAsync(
         string? resourceName = null,

src/Aspire.Cli/Backchannel/ResourceSnapshotWatcher.cs

@@ -16,6 +16,7 @@ internal sealed class ResourceSnapshotWatcher : IDisposable
     private readonly CancellationTokenSource _cts = new();
     private readonly TaskCompletionSource _initialLoadTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
     private readonly Task _watchTask;
+    private volatile Exception? _watchException;
 
     public ResourceSnapshotWatcher(IAppHostAuxiliaryBackchannel connection, bool includeHidden = false)
     {
@@ -61,10 +62,19 @@ private async Task WatchAsync(CancellationToken cancellationToken)
         }
         catch (Exception ex)
         {
-            _initialLoadTcs.TrySetException(ex);
+            if (!_initialLoadTcs.TrySetException(ex))
+            {
+                // Initial load already completed; store for callers to detect.
+                _watchException = ex;
+            }
         }
     }
 
+    /// <summary>
+    /// Gets the exception that terminated the watch loop after the initial load, or <see langword="null"/> if the watch is still running.
+    /// </summary>
+    public Exception? WatchException => _watchException;
+
     private void EnsureInitialLoadComplete()
     {
         if (!_initialLoadTcs.Task.IsCompletedSuccessfully)

src/Aspire.Cli/Commands/LogsCommand.cs

@@ -316,6 +316,8 @@ private static async Task<IList<LogEntry>> CollectLogsAsync(
     {
         var logParser = new LogParser(ConsoleColor.Black);
         var logEntries = new LogEntries(int.MaxValue) { BaseLineNumber = 1 };
+        // Snapshot the resource list once for the non-follow path since it doesn't change.
+        var allSnapshots = resourceWatcher.GetAllResources().ToList();
         await foreach (var logLine in connection.GetResourceLogsAsync(resourceName, follow: false, cancellationToken).ConfigureAwait(false))
         {
             // When streaming all resources, skip logs from hidden resources
@@ -328,7 +330,7 @@ private static async Task<IList<LogEntry>> CollectLogsAsync(
                 }
             }
 
-            logEntries.InsertSorted(ParseLogLine(logLine, logParser, resourceWatcher.GetAllResources()));
+            logEntries.InsertSorted(ParseLogLine(logLine, logParser, allSnapshots));
         }
         return logEntries.GetEntries();
     }

tests/Aspire.Cli.Tests/TestServices/TestAppHostAuxiliaryBackchannel.cs

@@ -71,7 +71,7 @@ public Task<List<ResourceSnapshot>> GetResourceSnapshotsAsync(bool includeHidden
 
         var snapshots = includeHidden
             ? ResourceSnapshots
-            : ResourceSnapshots.Where(s => !IsHiddenResource(s)).ToList();
+            : ResourceSnapshots.Where(s => !ResourceSnapshotMapper.IsHiddenResource(s)).ToList();
         return Task.FromResult(snapshots);
     }
 
@@ -88,7 +88,7 @@ public async IAsyncEnumerable<ResourceSnapshot> WatchResourceSnapshotsAsync(bool
 
         foreach (var snapshot in ResourceSnapshots)
         {
-            if (!includeHidden && IsHiddenResource(snapshot))
+            if (!includeHidden && ResourceSnapshotMapper.IsHiddenResource(snapshot))
             {
                 continue;
             }
@@ -98,11 +98,6 @@ public async IAsyncEnumerable<ResourceSnapshot> WatchResourceSnapshotsAsync(bool
         await Task.CompletedTask;
     }
 
-    private static bool IsHiddenResource(ResourceSnapshot snapshot)
-    {
-        return snapshot.IsHidden || string.Equals(snapshot.State, "Hidden", StringComparison.OrdinalIgnoreCase);
-    }
-
     public async IAsyncEnumerable<ResourceLogLine> GetResourceLogsAsync(
         string? resourceName = null,
         bool follow = false,