refactor: use System.Threading.CancellationToken instead of SourceGit.Commands.Command.CancelToken to cancel fetching information of selected commit

Signed-off-by: leo <longshuang@msn.cn>

src/Commands/Command.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Text;
 using System.Text.RegularExpressions;
+using System.Threading;
 
 using Avalonia.Threading;
 
@@ -10,11 +11,6 @@ namespace SourceGit.Commands
 {
     public partial class Command
     {
-        public class CancelToken
-        {
-            public bool Requested { get; set; } = false;
-        }
-
         public class ReadToEndResult
         {
             public bool IsSuccess { get; set; } = false;
@@ -30,7 +26,7 @@ namespace SourceGit.Commands
         }
 
         public string Context { get; set; } = string.Empty;
-        public CancelToken Cancel { get; set; } = null;
+        public CancellationToken CancellationToken { get; set; } = CancellationToken.None;
         public string WorkingDirectory { get; set; } = null;
         public EditorType Editor { get; set; } = EditorType.CoreEditor; // Only used in Exec() mode
         public string SSHKey { get; set; } = string.Empty;
@@ -43,36 +39,15 @@ namespace SourceGit.Commands
             var start = CreateGitStartInfo();
             var errs = new List<string>();
             var proc = new Process() { StartInfo = start };
-            var isCancelled = false;
 
             proc.OutputDataReceived += (_, e) =>
             {
-                if (Cancel != null && Cancel.Requested)
-                {
-                    isCancelled = true;
-                    proc.CancelErrorRead();
-                    proc.CancelOutputRead();
-                    if (!proc.HasExited)
-                        proc.Kill(true);
-                    return;
-                }
-
                 if (e.Data != null)
                     OnReadline(e.Data);
             };
 
             proc.ErrorDataReceived += (_, e) =>
             {
-                if (Cancel != null && Cancel.Requested)
-                {
-                    isCancelled = true;
-                    proc.CancelErrorRead();
-                    proc.CancelOutputRead();
-                    if (!proc.HasExited)
-                        proc.Kill(true);
-                    return;
-                }
-
                 if (string.IsNullOrEmpty(e.Data))
                 {
                     errs.Add(string.Empty);
@@ -97,9 +72,25 @@ namespace SourceGit.Commands
                 errs.Add(e.Data);
             };
 
+            var dummy = null as Process;
             try
             {
                 proc.Start();
+
+                // It not safe, please only use `CancellationToken` in readonly commands.
+                if (CancellationToken.CanBeCanceled)
+                {
+                    dummy = proc;
+                    CancellationToken.Register(() =>
+                    {
+                        if (dummy is { HasExited: false })
+                        {
+                            dummy.CancelErrorRead();
+                            dummy.CancelOutputRead();
+                            dummy.Kill();
+                        }
+                    });
+                }
             }
             catch (Exception e)
             {
@@ -113,10 +104,11 @@ namespace SourceGit.Commands
             proc.BeginErrorReadLine();
             proc.WaitForExit();
 
+            dummy = null;
             int exitCode = proc.ExitCode;
             proc.Close();
 
-            if (!isCancelled && exitCode != 0)
+            if (!CancellationToken.IsCancellationRequested && exitCode != 0)
             {
                 if (RaiseError)
                 {

src/ViewModels/CommitDetail.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Text.RegularExpressions;
+using System.Threading;
 using System.Threading.Tasks;
 
 using Avalonia.Controls;
@@ -171,7 +172,7 @@ namespace SourceGit.ViewModels
             _searchChangeFilter = null;
             _diffContext = null;
             _viewRevisionFileContent = null;
-            _cancelToken = null;
+            _cancellationSource = null;
             WebLinks.Clear();
             _revisionFiles = null;
             _revisionFileSearchSuggestion = null;
@@ -589,32 +590,36 @@ namespace SourceGit.ViewModels
             if (_commit == null)
                 return;
 
+            if (_cancellationSource is { IsCancellationRequested: false })
+                _cancellationSource.Cancel();
+
+            _cancellationSource = new CancellationTokenSource();
+            var token = _cancellationSource.Token;
+
             Task.Run(() =>
             {
                 var message = new Commands.QueryCommitFullMessage(_repo.FullPath, _commit.SHA).Result();
                 var links = ParseLinksInMessage(message);
+
+                if (!token.IsCancellationRequested)
                     Dispatcher.UIThread.Invoke(() => FullMessage = new Models.CommitFullMessage { Message = message, Links = links });
             });
 
             Task.Run(() =>
             {
                 var signInfo = new Commands.QueryCommitSignInfo(_repo.FullPath, _commit.SHA, !_repo.HasAllowedSignersFile).Result();
+                if (!token.IsCancellationRequested)
                     Dispatcher.UIThread.Invoke(() => SignInfo = signInfo);
             });
 
-            if (_cancelToken != null)
-                _cancelToken.Requested = true;
-
-            _cancelToken = new Commands.Command.CancelToken();
-
             if (Preferences.Instance.ShowChildren)
             {
                 Task.Run(() =>
                 {
                     var max = Preferences.Instance.MaxHistoryCommits;
-                    var cmdChildren = new Commands.QueryCommitChildren(_repo.FullPath, _commit.SHA, max) { Cancel = _cancelToken };
+                    var cmd = new Commands.QueryCommitChildren(_repo.FullPath, _commit.SHA, max) { CancellationToken = token };
-                    var children = cmdChildren.Result();
+                    var children = cmd.Result();
-                    if (!cmdChildren.Cancel.Requested)
+                    if (!token.IsCancellationRequested)
                         Dispatcher.UIThread.Post(() => Children = children);
                 });
             }
@@ -622,8 +627,8 @@ namespace SourceGit.ViewModels
             Task.Run(() =>
             {
                 var parent = _commit.Parents.Count == 0 ? "4b825dc642cb6eb9a060e54bf8d69288fbee4904" : _commit.Parents[0];
-                var cmdChanges = new Commands.CompareRevisions(_repo.FullPath, parent, _commit.SHA) { Cancel = _cancelToken };
+                var cmd = new Commands.CompareRevisions(_repo.FullPath, parent, _commit.SHA) { CancellationToken = token };
-                var changes = cmdChanges.Result();
+                var changes = cmd.Result();
                 var visible = changes;
                 if (!string.IsNullOrWhiteSpace(_searchChangeFilter))
                 {
@@ -635,7 +640,7 @@ namespace SourceGit.ViewModels
                     }
                 }
 
-                if (!cmdChanges.Cancel.Requested)
+                if (!token.IsCancellationRequested)
                 {
                     Dispatcher.UIThread.Post(() =>
                     {
@@ -873,7 +878,7 @@ namespace SourceGit.ViewModels
         private string _searchChangeFilter = string.Empty;
         private DiffContext _diffContext = null;
         private object _viewRevisionFileContent = null;
-        private Commands.Command.CancelToken _cancelToken = null;
+        private CancellationTokenSource _cancellationSource = null;
         private List<string> _revisionFiles = null;
         private string _revisionFileSearchFilter = string.Empty;
         private List<string> _revisionFileSearchSuggestion = null;