add HostSignal.AfterProcessStart to allow the users to obtain ID of a process that was started suspended (#2674)

Author: adamsitnik

src/BenchmarkDotNet/Engines/HostSignal.cs

@@ -7,6 +7,11 @@ public enum HostSignal
         /// </summary>
         BeforeProcessStart,
 
+        /// <summary>
+        /// right after we start the benchmarking process
+        /// </summary>
+        AfterProcessStart,
+
         /// <summary>
         /// before jitting, warmup
         /// </summary>

src/BenchmarkDotNet/Loggers/Broker.cs

@@ -15,20 +15,18 @@ internal class Broker
     {
         private readonly ILogger logger;
         private readonly Process process;
-        private readonly IDiagnoser diagnoser;
         private readonly AnonymousPipeServerStream inputFromBenchmark, acknowledgments;
-        private readonly DiagnoserActionParameters diagnoserActionParameters;
         private readonly ManualResetEvent finished;
 
         public Broker(ILogger logger, Process process, IDiagnoser diagnoser,
             BenchmarkCase benchmarkCase, BenchmarkId benchmarkId, AnonymousPipeServerStream inputFromBenchmark, AnonymousPipeServerStream acknowledgments)
         {
             this.logger = logger;
             this.process = process;
-            this.diagnoser = diagnoser;
+            this.Diagnoser = diagnoser;
             this.inputFromBenchmark = inputFromBenchmark;
             this.acknowledgments = acknowledgments;
-            diagnoserActionParameters = new DiagnoserActionParameters(process, benchmarkCase, benchmarkId);
+            DiagnoserActionParameters = new DiagnoserActionParameters(process, benchmarkCase, benchmarkId);
             finished = new ManualResetEvent(false);
 
             Results = new List<string>();
@@ -38,6 +36,10 @@ public Broker(ILogger logger, Process process, IDiagnoser diagnoser,
             process.Exited += OnProcessExited;
         }
 
+        internal IDiagnoser Diagnoser { get; }
+
+        internal DiagnoserActionParameters DiagnoserActionParameters { get; }
+
         internal List<string> Results { get; }
 
         internal List<string> PrefixedOutput { get; }
@@ -90,7 +92,7 @@ private void ProcessDataBlocking()
                 }
                 else if (Engine.Signals.TryGetSignal(line, out var signal))
                 {
-                    diagnoser?.Handle(signal, diagnoserActionParameters);
+                    Diagnoser?.Handle(signal, DiagnoserActionParameters);
 
                     writer.WriteLine(Engine.Signals.Acknowledgment);
 

src/BenchmarkDotNet/Toolchains/DotNetCli/DotNetCliExecutor.cs

@@ -83,9 +83,12 @@ private ExecuteResult Execute(BenchmarkCase benchmarkCase,
 
                 logger.WriteLineInfo($"// Execute: {process.StartInfo.FileName} {process.StartInfo.Arguments} in {process.StartInfo.WorkingDirectory}");
 
-                diagnoser?.Handle(HostSignal.BeforeProcessStart, new DiagnoserActionParameters(process, benchmarkCase, benchmarkId));
+                diagnoser?.Handle(HostSignal.BeforeProcessStart, broker.DiagnoserActionParameters);
 
                 process.Start();
+
+                diagnoser?.Handle(HostSignal.AfterProcessStart, broker.DiagnoserActionParameters);
+
                 processOutputReader.BeginRead();
 
                 process.EnsureHighPriority(logger);

src/BenchmarkDotNet/Toolchains/Executor.cs

@@ -79,6 +79,8 @@ private static ExecuteResult Execute(Process process, BenchmarkCase benchmarkCas
                 return new ExecuteResult(true, null, null, Array.Empty<string>(), Array.Empty<string>(), Array.Empty<string>(), launchIndex);
             }
 
+            broker.Diagnoser?.Handle(HostSignal.AfterProcessStart, broker.DiagnoserActionParameters);
+
             processOutputReader.BeginRead();
 
             process.EnsureHighPriority(logger);