Stop pip updates from corrupting the Python environment

src/Languages/lang_en.json

@@ -1842,5 +1842,7 @@
   "GitHub returned an empty access token.": "GitHub returned an empty access token.",
   "GitHub sign-in failed ({0}): {1}": "GitHub sign-in failed ({0}): {1}",
   "The GitHub sign-in code has expired. Please try again.": "The GitHub sign-in code has expired. Please try again.",
-  "WinGet repair exited with code {0}.": "WinGet repair exited with code {0}."
+  "WinGet repair exited with code {0}.": "WinGet repair exited with code {0}.",
+  "Waiting for another {0} operation to finish...": "Waiting for another {0} operation to finish...",
+  "A file of {package} is in use by another program. Close any program that may be using it, then try again": "A file of {package} is in use by another program. Close any program that may be using it, then try again"
 }

src/UniGetUI.PackageEngine.Enums/ManagerCapabilities.cs

@@ -42,6 +42,7 @@ public struct ManagerCapabilities
         public bool SupportsCustomScopesOnUpdate = true;
         public bool SupportsCustomScopesOnUninstall = true;
         public bool SupportsPreRelease = false;
+        public bool SerializesOperations = false;
         public bool SupportsCustomLocations = false;
         public bool SupportsCustomSources = false;
         public bool SupportsCustomPackageIcons = false;

src/UniGetUI.PackageEngine.Managers.Pip/Helpers/PipPkgOperationHelper.cs

@@ -94,14 +94,22 @@ int returnCode
                 return OperationVeredict.AutoRetry;
             }
 
-            if (package.OverridenOptions.Scope != PackageScope.User)
+            if (
+                operation is not OperationType.Update
+                && package.OverridenOptions.Scope != PackageScope.User
+            )
             {
                 package.OverridenOptions.Scope = PackageScope.User;
                 return OperationVeredict.AutoRetry;
             }
         }
 
-        if (output_string.Contains("--user") && package.OverridenOptions.Scope != PackageScope.User)
+        if (
+            operation is not OperationType.Update
+            && output_string.Contains("--user")
+            && !output_string.Contains("[WinError 32]")
+            && package.OverridenOptions.Scope != PackageScope.User
+        )
         {
             package.OverridenOptions.Scope = PackageScope.User;
             return OperationVeredict.AutoRetry;

src/UniGetUI.PackageEngine.Managers.Pip/Pip.cs

@@ -64,6 +64,7 @@ public Pip()
                 SupportsCustomScopes = true,
                 CanDownloadInstaller = true,
                 SupportsPreRelease = true,
+                SerializesOperations = true,
                 CanListDependencies = true,
                 SupportsProxy = ProxySupport.Yes,
                 SupportsProxyAuth = true,

src/UniGetUI.PackageEngine.Operations/AbstractOperation.cs

@@ -319,15 +319,14 @@ private async Task MainThreadCore(CancellationTokenSource runCancellation)
 
                 while (
                     FORCE_HOLD_QUEUE
-                    || (IndexInQueue(this) >= MAX_OPERATIONS && !SKIP_QUEUE)
+                    || (SlotsTakenAhead(this) >= MAX_OPERATIONS && !SKIP_QUEUE)
                 )
                 {
-                    int pos = IndexInQueue(this) - MAX_OPERATIONS + 1;
-
-                    if (pos == -1)
+                    if (IndexInQueue(this) - MAX_OPERATIONS + 1 == -1)
                         return;
                     // In this case, operation was canceled;
 
+                    int pos = SlotsTakenAhead(this) - MAX_OPERATIONS + 1;
                     if (pos != lastPos)
                     {
                         lastPos = pos;
@@ -646,6 +645,31 @@ public static int IndexInQueue(AbstractOperation operation)
             return OperationQueue.IndexOf(operation);
     }
 
+    internal bool IsWaitingForManager
+    {
+        get => _isWaitingForManager;
+        set => _isWaitingForManager = value;
+    }
+    private volatile bool _isWaitingForManager;
+
+    private static int SlotsTakenAhead(AbstractOperation operation)
+    {
+        lock (QueueLock)
+        {
+            int index = OperationQueue.IndexOf(operation);
+            if (index < 0)
+                return index;
+
+            int taken = 0;
+            for (int i = 0; i < index; i++)
+            {
+                if (!OperationQueue[i].IsWaitingForManager)
+                    taken++;
+            }
+            return taken;
+        }
+    }
+
     public static int QueueLength()
     {
         lock (QueueLock)

src/UniGetUI.PackageEngine.Operations/PackageOperations.cs

@@ -1,3 +1,4 @@
+using System.Collections.Concurrent;
 using System.Diagnostics;
 using System.Text;
 using UniGetUI.Core.Classes;
@@ -344,12 +345,53 @@ protected override async Task<OperationVeredict> PerformOperation()
 
             if (!ShouldUseAgentBroker())
             {
-                return await base.PerformOperation();
+                if (!Package.Manager.Capabilities.SerializesOperations)
+                    return await base.PerformOperation();
+
+                SemaphoreSlim gate = ManagerOperationGates.GetOrAdd(
+                    Package.Manager.Name,
+                    _ => new SemaphoreSlim(1, 1)
+                );
+                if (!await gate.WaitAsync(0))
+                {
+                    Line(
+                        CoreTools.Translate(
+                            "Waiting for another {0} operation to finish...",
+                            Package.Manager.DisplayName
+                        ),
+                        LineType.ProgressIndicator
+                    );
+                    IsWaitingForManager = true;
+                    try
+                    {
+                        await gate.WaitAsync(CancellationToken);
+                    }
+                    catch (OperationCanceledException)
+                    {
+                        return OperationVeredict.Canceled;
+                    }
+                    finally
+                    {
+                        IsWaitingForManager = false;
+                    }
+                }
+
+                try
+                {
+                    return await base.PerformOperation();
+                }
+                finally
+                {
+                    gate.Release();
+                }
             }
 
             return await PerformBrokerOperation();
         }
 
+        private static readonly ConcurrentDictionary<string, SemaphoreSlim> ManagerOperationGates =
+            new();
+
         /// <summary>
         /// Determines whether this operation should be routed through the agent broker.
         /// </summary>
@@ -1058,6 +1100,7 @@ List<string> Output
                     ExplainNotApplicableUpdate(Output, ReturnCode);
                 ExplainInstallerHashMismatch(ReturnCode);
                 ExplainApplicationCurrentlyRunning(Output, ReturnCode);
+                ExplainFileInUse(Output);
             }
 
             return Task.FromResult(veredict);
@@ -1197,6 +1240,17 @@ private void ExplainApplicationCurrentlyRunning(List<string> output, int returnC
 #endif
         }
 
+        private void ExplainFileInUse(List<string> output)
+        {
+            if (!output.Any(line => line.Contains("[WinError 32]", StringComparison.Ordinal)))
+                return;
+
+            Metadata.FailureMessage = CoreTools.Translate(
+                "A file of {package} is in use by another program. Close any program that may be using it, then try again",
+                new Dictionary<string, object?> { { "package", Package.Name } }
+            );
+        }
+
         private void ExplainNotApplicableUpdate(List<string> output, int returnCode)
         {
 #if WINDOWS