refactor: keep the workspace lock file empty

YKanBan.Tests/Storage/Workspace/WorkspaceLockTests.cs

@@ -5,7 +5,7 @@ using YKanBan.Tests.TestUtilities;
 namespace YKanBan.Tests.Storage.Workspace;
 
 /// <summary>
-/// Tests for exclusive lock acquisition, diagnostics and release.
+/// Tests for exclusive lock acquisition and release.
 /// </summary>
 [TestClass]
 public class WorkspaceLockTests
@@ -42,7 +42,7 @@ public class WorkspaceLockTests
     }
 
     [TestMethod]
-    public void LockFileContainsHolderDiagnosticsAfterRelease()
+    public void LockFileIsEmptyAfterRelease()
     {
         using var directory = new TempDirectory();
         WorkspaceInitializer.Initialize(directory.FullPath);
@@ -51,9 +51,7 @@ public class WorkspaceLockTests
         {
         }
 
-        // The file survives release and carries PID / machine name / time for humans.
-        string content = File.ReadAllText(WorkspacePaths.LockFile(directory.FullPath));
-        StringAssert.Contains(content, "pid=");
-        StringAssert.Contains(content, $"machine={Environment.MachineName}");
+        // The lock file survives release but carries no content; only the OS handle matters.
+        Assert.AreEqual(0L, new FileInfo(WorkspacePaths.LockFile(directory.FullPath)).Length);
     }
 }

YKanBan/Storage/StorageExceptions.cs

@@ -72,39 +72,15 @@ public sealed class WorkspaceLockException : YKanBanException
     /// </summary>
     public string LockFilePath { get; }
 
-    /// <summary>
-    /// Gets the best-effort holder diagnostics read from the lock file, or
-    /// <see langword="null"/> when they could not be read.
-    /// </summary>
-    public string? HolderDiagnostics { get; }
-
     /// <summary>
     /// Initializes the exception for a failed lock acquisition.
     /// </summary>
     /// <param name="lockFilePath">The lock file that is already held.</param>
-    /// <param name="holderDiagnostics">Diagnostics of the current holder, when readable.</param>
     /// <param name="innerException">The underlying I/O error.</param>
-    public WorkspaceLockException(string lockFilePath, string? holderDiagnostics, Exception innerException)
-        : base(BuildMessage(lockFilePath, holderDiagnostics), innerException)
+    public WorkspaceLockException(string lockFilePath, Exception innerException)
+        : base($"The workspace is locked by another instance: {lockFilePath}", innerException)
     {
         LockFilePath = lockFilePath;
-        HolderDiagnostics = holderDiagnostics;
-    }
-
-    /// <summary>
-    /// Composes the diagnostic message, appending holder details when they were readable.
-    /// </summary>
-    /// <param name="lockFilePath">The lock file that is already held.</param>
-    /// <param name="holderDiagnostics">Diagnostics of the current holder, when readable.</param>
-    /// <returns>The English diagnostic message.</returns>
-    private static string BuildMessage(string lockFilePath, string? holderDiagnostics)
-    {
-        string message = $"The workspace is locked by another instance: {lockFilePath}";
-        if (!string.IsNullOrEmpty(holderDiagnostics))
-        {
-            message += $" Lock holder: {holderDiagnostics}";
-        }
-        return message;
     }
 }
 

YKanBan/Storage/Workspace/WorkspaceLock.cs

@@ -1,11 +1,9 @@
-using System.Text;
-
 namespace YKanBan.Storage.Workspace;
 
 /// <summary>
 /// Exclusive, OS-enforced lock over a workspace's ykanban.lock. The handle is
-/// held until disposal, so crashes and power loss release it automatically.
-/// The lock file also carries PID / machine name / time for human diagnostics.
+/// held until disposal, so crashes and power loss release it automatically. The
+/// lock file is kept empty; only its exclusive OS handle carries meaning.
 /// </summary>
 public sealed class WorkspaceLock : IDisposable
 {
@@ -28,7 +26,7 @@ public sealed class WorkspaceLock : IDisposable
     public string LockFilePath { get; }
 
     /// <summary>
-    /// Acquires the workspace lock, writing this process's diagnostics into it.
+    /// Acquires the workspace lock, leaving the lock file empty.
     /// </summary>
     /// <param name="folderPath">The workspace folder to lock.</param>
     /// <returns>The held lock; dispose it to release.</returns>
@@ -40,7 +38,7 @@ public sealed class WorkspaceLock : IDisposable
         FileStream stream;
         try
         {
-            // FileShare.None gives the exclusive semantics; FileMode.Create truncates stale content.
+            // FileShare.None gives the exclusive semantics; FileMode.Create empties any stale file.
             stream = new FileStream(lockFilePath, FileMode.Create, FileAccess.Write, FileShare.None);
         }
         catch (DirectoryNotFoundException)
@@ -49,40 +47,12 @@ public sealed class WorkspaceLock : IDisposable
         }
         catch (IOException ex)
         {
-            throw new WorkspaceLockException(lockFilePath, ReadDiagnosticsBestEffort(lockFilePath), ex);
+            throw new WorkspaceLockException(lockFilePath, ex);
         }
 
-        // Write holder diagnostics so humans can identify the owning instance from the file alone.
-        string diagnostics = $"pid={Environment.ProcessId};machine={Environment.MachineName};time={DateTimeOffset.UtcNow:O}";
-        byte[] payload = Encoding.UTF8.GetBytes(diagnostics);
-        stream.Write(payload, 0, payload.Length);
-        stream.Flush();
         return new WorkspaceLock(stream, lockFilePath);
     }
 
-    /// <summary>
-    /// Attempts to read holder diagnostics from a lock file we failed to
-    /// acquire. The read is best-effort: a live FileShare.None holder makes the
-    /// file unreadable, in which case <see langword="null"/> is returned.
-    /// </summary>
-    /// <param name="lockFilePath">The lock file to read.</param>
-    /// <returns>The diagnostics text, or <see langword="null"/> when unreadable.</returns>
-    private static string? ReadDiagnosticsBestEffort(string lockFilePath)
-    {
-        try
-        {
-            return File.ReadAllText(lockFilePath);
-        }
-        catch (IOException)
-        {
-            return null;
-        }
-        catch (UnauthorizedAccessException)
-        {
-            return null;
-        }
-    }
-
     /// <summary>
     /// Releases the exclusive handle. The lock file itself is intentionally
     /// left on disk; the OS releases the handle even on a crash.