Capture standard error.

Author: timcassell

src/BenchmarkDotNet/Helpers/ProcessHelper.cs

@@ -63,7 +63,7 @@ internal static class ProcessHelper
                 UseShellExecute = false,
                 CreateNoWindow = true,
                 RedirectStandardOutput = true,
-                RedirectStandardError = true
+                RedirectStandardError = includeErrors
             };
 
             foreach (var environmentVariable in environmentVariables ?? [])

src/BenchmarkDotNet/Toolchains/DotNetCli/DotNetCliExecutor.cs

@@ -80,13 +80,13 @@ private async ValueTask<ExecuteResult> Execute(BenchmarkCase benchmarkCase,
                 $"{executableName.EscapeCommandLine()} {benchmarkId.ToArguments(port, diagnoserRunMode)}",
                 redirectStandardOutput: true,
                 redirectStandardInput: false,
-                redirectStandardError: false); // #1629
+                redirectStandardError: true);
 
             startInfo.SetEnvironmentVariables(benchmarkCase, resolver);
 
             using Process process = new() { StartInfo = startInfo };
             using ProcessCleanupHelper processCleanupHelper = new(process, logger);
-            using AsyncProcessOutputReader processOutputReader = new(process, logOutput: true, logger, readStandardError: false);
+            using AsyncProcessOutputReader processOutputReader = new(process, logOutput: true, logger, readStandardError: true);
 
             bool processOutputStarted = false;
             List<string> results;
@@ -135,6 +135,15 @@ private async ValueTask<ExecuteResult> Execute(BenchmarkCase benchmarkCase,
                 }
             }
 
+            if (process.HasExited && process.ExitCode != 0)
+            {
+                string stderr = processOutputReader.GetErrorText();
+                if (!string.IsNullOrEmpty(stderr))
+                {
+                    logger.WriteLineError($"// Benchmark process stderr: {stderr}");
+                }
+            }
+
             return new ExecuteResult(true,
                 process.HasExited ? process.ExitCode : null,
                 process.Id,

src/BenchmarkDotNet/Toolchains/Executor.cs

@@ -63,7 +63,7 @@ private static async ValueTask<ExecuteResult> ExecuteCore(BenchmarkCase benchmar
 
             using Process process = new() { StartInfo = CreateStartInfo(benchmarkCase, artifactsPaths, args, resolver) };
             using ProcessCleanupHelper processCleanupHelper = new(process, logger);
-            using AsyncProcessOutputReader processOutputReader = new(process, logOutput: true, logger, readStandardError: false);
+            using AsyncProcessOutputReader processOutputReader = new(process, logOutput: true, logger, readStandardError: true);
 
             List<string> results;
             List<string> prefixedOutput;
@@ -121,6 +121,15 @@ private static async ValueTask<ExecuteResult> ExecuteCore(BenchmarkCase benchmar
                 }
             }
 
+            if (process.HasExited && process.ExitCode != 0)
+            {
+                string stderr = processOutputReader.GetErrorText();
+                if (!string.IsNullOrEmpty(stderr))
+                {
+                    logger.WriteLineError($"// Benchmark process stderr: {stderr}");
+                }
+            }
+
             if (results.Any(line => line.Contains("BadImageFormatException")))
                 logger.WriteLineError("You are probably missing <PlatformTarget>AnyCPU</PlatformTarget> in your .csproj file.");
 
@@ -140,7 +149,7 @@ private static ProcessStartInfo CreateStartInfo(BenchmarkCase benchmarkCase, Art
                 UseShellExecute = false,
                 RedirectStandardOutput = true,
                 RedirectStandardInput = false,
-                RedirectStandardError = false, // #1629
+                RedirectStandardError = true,
                 CreateNoWindow = true,
                 WorkingDirectory = null // by default it's null
             };

src/BenchmarkDotNet/Toolchains/MonoWasm/WasmExecutor.cs

@@ -145,7 +145,7 @@ private static async ValueTask<ExecuteResult> Execute(BenchmarkCase benchmarkCas
             {
                 using ProcessCleanupHelper processCleanupHelper = new(processListener.Process, logger);
                 bool isFileBasedIpc = processListener.Listener is FileStdOutListener;
-                using AsyncProcessOutputReader processOutputReader = new(processListener.Process, logOutput: !isFileBasedIpc, logger, readStandardError: false, channelStandardOutput: isFileBasedIpc);
+                using AsyncProcessOutputReader processOutputReader = new(processListener.Process, logOutput: !isFileBasedIpc, logger, readStandardError: true, channelStandardOutput: isFileBasedIpc);
 
                 if (isFileBasedIpc)
                 {
@@ -175,7 +175,7 @@ private static Process CreateProcess(BenchmarkCase benchmarkCase, ArtifactsPaths
                 UseShellExecute = false,
                 RedirectStandardOutput = true,
                 RedirectStandardInput = false, // not supported by WASM!
-                RedirectStandardError = false, // #1629
+                RedirectStandardError = true,
                 CreateNoWindow = true
             };
 
@@ -235,6 +235,15 @@ await broker.ProcessData(cancellationToken)
                 }
             }
 
+            if (process.HasExited && process.ExitCode != 0)
+            {
+                string stderr = processOutputReader.GetErrorText();
+                if (!string.IsNullOrEmpty(stderr))
+                {
+                    logger.WriteLineError($"// Benchmark process stderr: {stderr}");
+                }
+            }
+
             return new ExecuteResult(true,
                 process.HasExited ? process.ExitCode : null,
                 process.Id,