Make compat binary console output non-blocking

source/Halibut.TestUtils.CompatBinary.Base/BackwardsCompatProgramBase.cs

@@ -10,6 +10,7 @@ public class BackwardsCompatProgramBase
     {
         public static async Task<int> Main()
         {
+            NonBlockingConsoleWriter.Install();
             using var cancellationTokenSource = new CancellationTokenSource(SettingsHelper.GetTestTimeout());
             using var registration = cancellationTokenSource.Token.Register(() =>
             {

source/Halibut.TestUtils.CompatBinary.Base/LogUtils/NonBlockingConsoleWriter.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Concurrent;
+using System.IO;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+using System.Text;
+using System.Threading;
+
+namespace Halibut.TestUtils.SampleProgram.Base.LogUtils
+{
+    /// <summary>
+    /// The test reads our stdout through a pipe. If it stops reading, a blocking Console.Write
+    /// freezes Halibut mid-exchange, so writes are queued and dropped when the queue is full.
+    /// </summary>
+    public class NonBlockingConsoleWriter : TextWriter
+    {
+        const int MaxQueuedWrites = 10_000;
+
+        readonly TextWriter destination;
+        readonly BlockingCollection<string> queue = new(MaxQueuedWrites);
+        long droppedWrites;
+
+        NonBlockingConsoleWriter(Stream destination)
+        {
+            this.destination = new StreamWriter(destination, new UTF8Encoding(false)) { AutoFlush = false };
+            new Thread(Drain) { IsBackground = true, Name = "NonBlockingConsoleWriter" }.Start();
+        }
+
+        public static void Install()
+        {
+            Console.SetOut(new NonBlockingConsoleWriter(OpenStandardStream(1, Console.OpenStandardOutput)));
+            Console.SetError(new NonBlockingConsoleWriter(OpenStandardStream(2, Console.OpenStandardError)));
+        }
+
+        // On Unix the console stream locks Console.Out while writing, so a stalled pipe would
+        // still block every Console.WriteLine. Write to the raw file descriptor instead.
+        static Stream OpenStandardStream(int fileDescriptor, Func<Stream> openConsoleStream)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return openConsoleStream();
+            return new FileStream(new SafeFileHandle((IntPtr)fileDescriptor, ownsHandle: false), FileAccess.Write, 1);
+        }
+
+        public override Encoding Encoding => destination.Encoding;
+
+        public override void Write(char value) => Enqueue(value.ToString());
+
+        public override void Write(string? value)
+        {
+            if (value is not null) Enqueue(value);
+        }
+
+        public override void WriteLine(string? value) => Enqueue(value + new string(CoreNewLine));
+
+        void Enqueue(string value)
+        {
+            if (!queue.TryAdd(value)) Interlocked.Increment(ref droppedWrites);
+        }
+
+        void Drain()
+        {
+            foreach (var value in queue.GetConsumingEnumerable())
+            {
+                var dropped = Interlocked.Exchange(ref droppedWrites, 0);
+                if (dropped > 0) destination.WriteLine($"[NonBlockingConsoleWriter dropped {dropped} writes]");
+
+                destination.Write(value);
+                if (queue.Count == 0) destination.Flush();
+            }
+        }
+    }
+}