kill process on purge

Author: SimonCropp

src/DiffEngineTray.Tests/FilePurgerTest.cs

@@ -0,0 +1,101 @@
+public class FilePurgerTest
+{
+    [Test]
+    public async Task DeleteSucceeds_WhenFileNotLocked()
+    {
+        var file = Path.Combine(Path.GetTempPath(), $"FilePurgerTest_{Guid.NewGuid()}.verified.txt");
+        File.WriteAllText(file, "content");
+
+        var result = FilePurger.TryDeleteWithLockKill(file);
+
+        await Assert.That(result.Deleted).IsTrue();
+        await Assert.That(result.Exception).IsNull();
+        await Assert.That(File.Exists(file)).IsFalse();
+    }
+
+    [Test]
+    public async Task DeleteSucceeds_WhenFileDoesNotExist()
+    {
+        var file = Path.Combine(Path.GetTempPath(), $"FilePurgerTest_{Guid.NewGuid()}.verified.txt");
+
+        var result = FilePurger.TryDeleteWithLockKill(file);
+
+        await Assert.That(result.Deleted).IsTrue();
+        await Assert.That(result.Exception).IsNull();
+    }
+
+    [Test]
+    public async Task DeleteSucceeds_WhenFileLocked_KillsLockingProcess()
+    {
+        var file = Path.Combine(Path.GetTempPath(), $"FilePurgerTest_{Guid.NewGuid()}.verified.txt");
+        File.WriteAllText(file, "content");
+
+        var lockProcess = StartFileLockProcess(file);
+
+        try
+        {
+            await Assert.That(IsFileLocked(file)).IsTrue();
+
+            var result = FilePurger.TryDeleteWithLockKill(file);
+
+            await Assert.That(result.Deleted).IsTrue();
+            await Assert.That(result.Exception).IsNull();
+            await Assert.That(File.Exists(file)).IsFalse();
+
+            var exited = lockProcess.WaitForExit(5000);
+            await Assert.That(exited).IsTrue();
+        }
+        finally
+        {
+            if (!lockProcess.HasExited)
+            {
+                lockProcess.Kill();
+            }
+
+            lockProcess.Dispose();
+
+            if (File.Exists(file))
+            {
+                File.Delete(file);
+            }
+        }
+    }
+
+    static Process StartFileLockProcess(string path)
+    {
+        var script = $"$f = [System.IO.File]::Open('{path.Replace("'", "''")}', 'Open', 'ReadWrite', 'None'); [Console]::WriteLine('locked'); Start-Sleep -Seconds 60";
+        var process = new Process
+        {
+            StartInfo = new()
+            {
+                FileName = "powershell.exe",
+                Arguments = $"-NoProfile -Command \"{script}\"",
+                UseShellExecute = false,
+                CreateNoWindow = true,
+                RedirectStandardOutput = true
+            }
+        };
+        process.Start();
+
+        var line = process.StandardOutput.ReadLine();
+        if (line != "locked")
+        {
+            throw new InvalidOperationException($"Expected 'locked' but got '{line}'");
+        }
+
+        return process;
+    }
+
+    static bool IsFileLocked(string path)
+    {
+        try
+        {
+            using var stream = File.Open(path, FileMode.Open, FileAccess.ReadWrite, FileShare.None);
+            return false;
+        }
+        catch (IOException)
+        {
+            return true;
+        }
+    }
+}

src/DiffEngineTray/FilePurger.cs

@@ -53,36 +53,64 @@ static void DeleteFiles(string[] files)
         for (var index = 0; index < files.Length; index++)
         {
             var file = files[index];
-            try
+            var result = TryDeleteWithLockKill(file);
+            if (result.Deleted)
             {
-                if (File.Exists(file))
-                {
-                    File.Delete(file);
-                }
+                continue;
+            }
+
+            var failedResult = AskQuestion(
+                $"""
+                 Could not delete file: {file}
+                 Exception: {result.Exception!.Message}
+                 """,
+                "Delete failed",
+                MessageBoxButtons.AbortRetryIgnore);
+
+            if (failedResult == DialogResult.Abort)
+            {
+                return;
+            }
+
+            if (failedResult == DialogResult.Retry)
+            {
+                index--;
+            }
+        }
+    }
+
+    internal static DeleteResult TryDeleteWithLockKill(string file)
+    {
+        try
+        {
+            if (File.Exists(file))
+            {
+                File.Delete(file);
             }
-            catch (Exception exception)
+
+            return new(true, null);
+        }
+        catch (Exception exception)
+        {
+            if (FileLockKiller.KillLockingProcesses(file))
             {
-                var failedResult = AskQuestion(
-                    $"""
-                     Could not delete file: {file}
-                     Exception: {exception.Message}
-                     """,
-                    "Delete failed",
-                    MessageBoxButtons.AbortRetryIgnore);
-
-                if (failedResult == DialogResult.Abort)
+                try
                 {
-                    return;
+                    File.Delete(file);
+                    return new(true, null);
                 }
-
-                if (failedResult == DialogResult.Retry)
+                catch (Exception retryException)
                 {
-                    index--;
+                    return new(false, retryException);
                 }
             }
+
+            return new(false, exception);
         }
     }
 
+    internal record DeleteResult(bool Deleted, Exception? Exception);
+
     static DialogResult AskQuestion(string text, string caption, MessageBoxButtons buttons) =>
         MessageBox.Show(
             text,