Keep a media process and its exit state usable by the caller that started it

1 files changed, 103 insertions, 0 deletions

diff --git a/tests/Jellyfin.MediaEncoding.Tests/Encoder/ProcessWrapperTests.cs b/tests/Jellyfin.MediaEncoding.Tests/Encoder/ProcessWrapperTests.cs
new file mode 100644
index 0000000000..141164815c
--- /dev/null
+++ b/tests/Jellyfin.MediaEncoding.Tests/Encoder/ProcessWrapperTests.cs
@@ -0,0 +1,103 @@
+using System;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.MediaEncoding.Encoder;
+using MediaBrowser.Model.Globalization;
+using MediaBrowser.Model.IO;
+using MediaBrowser.Model.MediaInfo;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.MediaEncoding.Tests.Encoder;
+
+public class ProcessWrapperTests
+{
+    [Fact]
+    public async Task ExitedProcess_StaysUsableForTheCallerThatStartedIt()
+    {
+        using var process = CreateProcess();
+        using var exitHandled = new ManualResetEventSlim(false);
+
+        using (var wrapper = new MediaEncoder.ProcessWrapper(process, CreateEncoder()))
+        {
+            // Subscribed after the wrapper, so by the time this is set the wrapper's own handler has
+            // already run: whatever it does to the process has happened.
+            process.Exited += (_, _) => exitHandled.Set();
+
+            process.Start();
+            await process.WaitForExitAsync(TestContext.Current.CancellationToken).ConfigureAwait(true);
+
+            Assert.True(exitHandled.Wait(TimeSpan.FromSeconds(15), TestContext.Current.CancellationToken), "The process never raised Exited.");
+
+            // The caller still owns the process here. Disposing it from the exit handler handed
+            // whoever exited quickest an ObjectDisposedException out of these three lines.
+            var output = await process.StandardOutput.ReadToEndAsync(TestContext.Current.CancellationToken).ConfigureAwait(true);
+            Assert.Equal("jellyfin", output.Trim());
+
+            Assert.True(wrapper.HasExited);
+            Assert.Equal(3, wrapper.ExitCode);
+        }
+    }
+
+    [Fact]
+    public async Task ExitState_IsReadableBeforeTheExitEventArrives()
+    {
+        using var process = CreateProcess();
+
+        using (var wrapper = new MediaEncoder.ProcessWrapper(process, CreateEncoder()))
+        {
+            process.Start();
+            await process.WaitForExitAsync(TestContext.Current.CancellationToken).ConfigureAwait(true);
+
+            // The exit event is raised on the thread pool and can lag behind the wait that just
+            // returned, so neither of these may depend on it having arrived.
+            Assert.True(wrapper.HasExited);
+            Assert.Equal(3, wrapper.ExitCode);
+        }
+    }
+
+    [Fact]
+    public async Task ExitCode_SurvivesDisposal()
+    {
+        using var process = CreateProcess();
+        var wrapper = new MediaEncoder.ProcessWrapper(process, CreateEncoder());
+
+        process.Start();
+        await process.WaitForExitAsync(TestContext.Current.CancellationToken).ConfigureAwait(true);
+
+        var exitCode = wrapper.ExitCode;
+        wrapper.Dispose();
+
+        Assert.Equal(exitCode, wrapper.ExitCode);
+        Assert.True(wrapper.HasExited);
+    }
+
+    private static MediaEncoder CreateEncoder()
+        => new(
+            Mock.Of<ILogger<MediaEncoder>>(),
+            Mock.Of<IServerConfigurationManager>(),
+            Mock.Of<IFileSystem>(),
+            Mock.Of<IBlurayExaminer>(),
+            Mock.Of<ILocalizationManager>(),
+            new ConfigurationBuilder().Build(),
+            Mock.Of<IServerConfigurationManager>());
+
+    // Writes to stdout and exits immediately with a non-zero code, standing in for the ffprobe that
+    // rejects a file outright - the process that used to win the race against its own caller.
+    private static Process CreateProcess()
+    {
+        var startInfo = OperatingSystem.IsWindows()
+            ? new ProcessStartInfo("cmd.exe", "/c echo jellyfin & exit 3")
+            : new ProcessStartInfo("/bin/sh", "-c \"printf 'jellyfin\\n'; exit 3\"");
+
+        startInfo.CreateNoWindow = true;
+        startInfo.UseShellExecute = false;
+        startInfo.RedirectStandardOutput = true;
+
+        return new Process { StartInfo = startInfo, EnableRaisingEvents = true };
+    }
+}