Fix for #22

MedallionShell.Tests/PlatformCompatibilityTest.cs

@@ -18,9 +18,18 @@ public class PlatformCompatibilityTest
         [TestMethod]
         public void TestWriteAfterExit() => RunTest(() => PlatformCompatibilityTests.TestWriteAfterExit());
 
+        [TestMethod]
+        public void TestFlushAfterExit() => RunTest(() => PlatformCompatibilityTests.TestFlushAfterExit());
+
         [TestMethod]
         public void TestExitWithMinusOne() => RunTest(() => PlatformCompatibilityTests.TestExitWithMinusOne());
 
+        [TestMethod]
+        public void TestExitWithOne() => RunTest(() => PlatformCompatibilityTests.TestExitWithOne());
+
+        [TestMethod]
+        public void TestBadProcessFile() => RunTest(() => PlatformCompatibilityTests.TestBadProcessFile());
+
         private static void RunTest(Expression<Action> testMethod)
         {
             var compiled = testMethod.Compile();

MedallionShell/MedallionShell.csproj

@@ -6,7 +6,7 @@
 
   <PropertyGroup>
     <RootNamespace>Medallion.Shell</RootNamespace>
-    <Version>1.5.0</Version>
+    <Version>1.5.1</Version>
     <Authors>Michael Adelson</Authors>
     <Description>A lightweight library that simplifies working with processes in .NET</Description>
     <Copyright>Copyright © 2017 Michael Adelson</Copyright>
@@ -16,7 +16,7 @@
     <PackageProjectUrl>https://github.com/madelson/MedallionShell</PackageProjectUrl>
     <RepositoryUrl />
     <FileVersion>1.0.0.0</FileVersion>
-    <PackageReleaseNotes>Added ToString() override for Commands to simplify debugging. WindowsCommandLineSyntax no longer quotes arguments unnecessarily.</PackageReleaseNotes>
+    <PackageReleaseNotes>See https://github.com/madelson/MedallionShell#release-notes</PackageReleaseNotes>
   </PropertyGroup>
 
   <PropertyGroup>

MedallionShell/PlatformCompatibilityHelper.cs

@@ -35,5 +35,45 @@ public static int SafeGetExitCode(this Process process)
 
             return process.ExitCode;
         }
+
+        /// <summary>
+        /// Starts the given <paramref name="process"/> and captures the standard IO streams. This method works around Mono.Android-specific
+        /// issue https://github.com/madelson/MedallionShell/issues/22, where a process that exits quickly causes the initialization of
+        /// the standard input writer to fail (since setting AutoFlush = true triggers a write which on Mono crashes for a closed process).
+        /// 
+        /// If https://github.com/mono/mono/issues/8478 is ever addressed, we wouldn't need this any more.
+        /// </summary>
+        public static bool SafeStart(this Process process, out StreamWriter standardInput, out StreamReader standardOutput, out StreamReader standardError)
+        {
+            var redirectStandardInput = process.StartInfo.RedirectStandardInput;
+            var redirectStandardOutput = process.StartInfo.RedirectStandardOutput;
+            var redirectStandardError = process.StartInfo.RedirectStandardError;
+
+            try
+            {
+                process.Start();
+
+                // adding this code allows for a sort-of replication of
+                // https://github.com/madelson/MedallionShell/issues/22 on non-Android platforms
+                //process.StandardInput.BaseStream.Write(new byte[1000], 0, 1000);
+                //process.StandardInput.BaseStream.Flush();
+            }
+            catch (IOException ex) 
+                // note that AFAIK the exact type check here isn't necessary, but it seems more robust against
+                // other types of IOExceptions (e. g. FileNotFoundException, PathTooLongException) that could in
+                // theory be thrown here and trigger this
+                when (IsMono && ex.GetType() == typeof(IOException))
+            {
+                standardInput = redirectStandardInput ? new StreamWriter(Stream.Null, Console.InputEncoding) { AutoFlush = true } : null;
+                standardOutput = redirectStandardOutput ? new StreamReader(Stream.Null, Console.OutputEncoding) : null;
+                standardError = redirectStandardError ? new StreamReader(Stream.Null, Console.OutputEncoding) : null;
+                return false;
+            }
+
+            standardInput = redirectStandardInput ? process.StandardInput : null;
+            standardOutput = redirectStandardOutput ? process.StandardOutput : null;
+            standardError = redirectStandardError ? process.StandardError : null;
+            return true;
+        }
     }
 }

MedallionShell/ProcessCommand.cs

@@ -36,29 +36,28 @@ internal sealed class ProcessCommand : Command
 
             var processMonitoringTask = CreateProcessMonitoringTask(this.process);
 
-            this.process.Start();
-
+            this.process.SafeStart(out var processStandardInput, out var processStandardOutput, out var processStandardError);
+            
             var ioTasks = new List<Task>(capacity: 2);
             if (startInfo.RedirectStandardOutput)
             {
-                this.standardOutputReader = new InternalProcessStreamReader(this.process.StandardOutput);
+                this.standardOutputReader = new InternalProcessStreamReader(processStandardOutput);
                 ioTasks.Add(this.standardOutputReader.Task);
             }
             if (startInfo.RedirectStandardError)
             {
-                this.standardErrorReader = new InternalProcessStreamReader(this.process.StandardError);
+                this.standardErrorReader = new InternalProcessStreamReader(processStandardError);
                 ioTasks.Add(this.standardErrorReader.Task);
             }
             if (startInfo.RedirectStandardInput)
             {
                 // unfortunately, changing the encoding can't be done via ProcessStartInfo so we have to do it manually here.
                 // See https://github.com/dotnet/corefx/issues/20497
 
-                var originalStandardInput = this.process.StandardInput;
-                var wrappedStream = PlatformCompatibilityHelper.WrapStandardInputStreamIfNeeded(originalStandardInput.BaseStream);
-                var standardInputEncodingToUse = standardInputEncoding ?? originalStandardInput.Encoding;
-                var streamWriter = wrappedStream == originalStandardInput.BaseStream && Equals(standardInputEncodingToUse, originalStandardInput.Encoding)
-                    ? originalStandardInput
+                var wrappedStream = PlatformCompatibilityHelper.WrapStandardInputStreamIfNeeded(processStandardInput.BaseStream);
+                var standardInputEncodingToUse = standardInputEncoding ?? processStandardInput.Encoding;
+                var streamWriter = wrappedStream == processStandardInput.BaseStream && Equals(standardInputEncodingToUse, processStandardInput.Encoding)
+                    ? processStandardInput
                     : new StreamWriter(wrappedStream, standardInputEncodingToUse);
                 this.standardInput = new ProcessStreamWriter(streamWriter);
             }

SampleCommand/PlatformCompatibilityTests.cs

@@ -1,6 +1,8 @@
 using Medallion.Shell;
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
+using System.IO;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -16,6 +18,16 @@ public static void TestWriteAfterExit()
             var command = Command.Run(SampleCommandPath, "exit", 1);
             command.Wait();
             command.StandardInput.WriteLine(); // no-op
+            command.StandardInput.BaseStream.WriteAsync(new byte[1], 0, 1).Wait(); // no-op
+        }
+
+        public static void TestFlushAfterExit()
+        {
+            var command = Command.Run(SampleCommandPath, "exit", 1);
+            command.Wait();
+            command.StandardInput.Flush();
+            command.StandardInput.BaseStream.Flush();
+            command.StandardInput.BaseStream.FlushAsync();
         }
 
         public static void TestReadAfterExit()
@@ -40,5 +52,34 @@ public static void TestExitWithMinusOne()
             var command = Command.Run(SampleCommandPath, "exit", -1);
             if (command.Result.ExitCode != -1) { throw new InvalidOperationException($"Was: {command.Result.ExitCode}"); }
         }
+
+        /// <summary>
+        /// See PlatformCompatibilityHelper.SafeStart comment
+        /// </summary>
+        public static void TestExitWithOne()
+        {
+            var command = Command.Run(SampleCommandPath, "exit", 1);
+            if (command.Result.ExitCode != 1) { throw new InvalidOperationException($"Was: {command.Result.ExitCode}"); }
+        }
+
+        public static void TestBadProcessFile()
+        {
+            var baseDirectory = Path.GetDirectoryName(SampleCommandPath);
+
+            AssertThrows<Win32Exception>(() => Command.Run(baseDirectory));
+            AssertThrows<Win32Exception>(() => Command.Run(Path.Combine(baseDirectory, "DOES_NOT_EXIST.exe")));
+        }
+
+        private static void AssertThrows<TException>(Action action) where TException : Exception
+        {
+            try { action(); }
+            catch (Exception ex)
+            {
+                if (ex.GetType() != typeof(TException)) { throw new InvalidOperationException($"Expected {typeof(TException)} but got {ex.GetType()}"); }
+                return;
+            }
+
+            throw new InvalidOperationException($"Expected {typeof(TException)}, but no exception was thrown");
+        }
     }
 }