Fix crash when searching in the Python Packages dialog

StabilityMatrix.Avalonia/ViewModels/Dialogs/PythonPackagesItemViewModel.cs

@@ -4,13 +4,11 @@
 using StabilityMatrix.Avalonia.ViewModels.Base;
 using StabilityMatrix.Core.Exceptions;
 using StabilityMatrix.Core.Helper;
-using StabilityMatrix.Core.Models.FileInterfaces;
 using StabilityMatrix.Core.Python;
-using StabilityMatrix.Core.Services;
 
 namespace StabilityMatrix.Avalonia.ViewModels.Dialogs;
 
-public partial class PythonPackagesItemViewModel(ISettingsManager settingsManager) : ViewModelBase
+public partial class PythonPackagesItemViewModel : ViewModelBase
 {
     [ObservableProperty]
     private PipPackageInfo package;
@@ -81,9 +79,9 @@ value is null
     /// <summary>
     /// Loads the pip show result if not already loaded
     /// </summary>
-    public async Task LoadExtraInfo(DirectoryPath venvPath, PyBaseInstall pyBaseInstall)
+    public async Task LoadExtraInfo(Func<Task<IPyVenvRunner>> createVenvRunner)
     {
-        if (PipShowResult is not null)
+        if (PipShowResult is not null || IsLoading)
         {
             return;
         }
@@ -98,11 +96,7 @@ public async Task LoadExtraInfo(DirectoryPath venvPath, PyBaseInstall pyBaseInst
             }
             else
             {
-                await using var venvRunner = await pyBaseInstall.CreateVenvRunnerAsync(
-                    venvPath,
-                    workingDirectory: venvPath.Parent,
-                    environmentVariables: settingsManager.Settings.EnvironmentVariables
-                );
+                await using var venvRunner = await createVenvRunner();
 
                 PipShowResult = await venvRunner.PipShow(Package.Name);
 

StabilityMatrix.Avalonia/ViewModels/Dialogs/PythonPackagesViewModel.cs

@@ -44,6 +44,20 @@ public partial class PythonPackagesViewModel : ContentDialogViewModelBase
     private readonly IPrerequisiteHelper prerequisiteHelper;
     private PyBaseInstall? pyBaseInstall;
 
+    /// <summary>
+    /// Lets only one package's details load at a time. Typing in the search box moves the
+    /// selection on almost every keystroke, which would otherwise start overlapping pip
+    /// processes against the same venv (each one rewriting its pyvenv.cfg).
+    /// </summary>
+    private readonly SemaphoreSlim extraInfoLock = new(1, 1);
+
+    private CancellationTokenSource? extraInfoCts;
+
+    /// <summary>
+    /// Replaces how venv runners are created, so tests can run without a real Python install.
+    /// </summary>
+    internal Func<Task<IPyVenvRunner>>? VenvRunnerFactory { get; set; }
+
     public DirectoryPath? VenvPath { get; set; }
 
     public PyVersion? PythonVersion { get; set; }
@@ -85,7 +99,7 @@ private void PostConstruct()
             .Connect()
             .DeferUntilLoaded()
             .Filter(searchPredicate)
-            .Transform(p => new PythonPackagesItemViewModel(settingsManager) { Package = p })
+            .Transform(p => new PythonPackagesItemViewModel { Package = p })
             .SortBy(vm => vm.Package.Name)
             .ObserveOn(SynchronizationContext.Current!)
             .Bind(Packages)
@@ -107,17 +121,7 @@ private async Task Refresh()
             }
             else
             {
-                pyBaseInstall ??= new PyBaseInstall(
-                    await pyInstallationManager.GetInstallationAsync(
-                        PythonVersion ?? PyInstallationManager.Python_3_10_11
-                    )
-                );
-
-                await using var venvRunner = await pyBaseInstall.CreateVenvRunnerAsync(
-                    VenvPath,
-                    workingDirectory: VenvPath.Parent,
-                    environmentVariables: settingsManager.Settings.EnvironmentVariables
-                );
+                await using var venvRunner = await CreateVenvRunnerAsync();
 
                 var packages = await venvRunner.PipList();
 
@@ -143,16 +147,7 @@ private async Task RefreshBackground()
         if (VenvPath is null)
             return;
 
-        pyBaseInstall ??= new PyBaseInstall(
-            await pyInstallationManager.GetInstallationAsync(
-                PythonVersion ?? PyInstallationManager.Python_3_10_11
-            )
-        );
-        await using var venvRunner = await pyBaseInstall.CreateVenvRunnerAsync(
-            VenvPath,
-            workingDirectory: VenvPath.Parent,
-            environmentVariables: settingsManager.Settings.EnvironmentVariables
-        );
+        await using var venvRunner = await CreateVenvRunnerAsync();
 
         var packages = await venvRunner.PipList();
 
@@ -169,19 +164,83 @@ await pyInstallationManager.GetInstallationAsync(
         });
     }
 
+    private async Task<IPyVenvRunner> CreateVenvRunnerAsync()
+    {
+        if (VenvRunnerFactory is not null)
+        {
+            return await VenvRunnerFactory();
+        }
+
+        ArgumentNullException.ThrowIfNull(VenvPath);
+
+        pyBaseInstall ??= new PyBaseInstall(
+            await pyInstallationManager.GetInstallationAsync(
+                PythonVersion ?? PyInstallationManager.Python_3_10_11
+            )
+        );
+
+        return await pyBaseInstall.CreateVenvRunnerAsync(
+            VenvPath,
+            workingDirectory: VenvPath.Parent,
+            environmentVariables: settingsManager.Settings.EnvironmentVariables
+        );
+    }
+
     /// <summary>
     /// Load the selected package's show info if not already loaded
     /// </summary>
     partial void OnSelectedPackageChanged(PythonPackagesItemViewModel? value)
     {
-        if (value is null)
+        // A load still waiting for its turn is no longer wanted once the selection moves on
+        extraInfoCts?.Cancel();
+        extraInfoCts?.Dispose();
+        extraInfoCts = null;
+
+        if (value is null || (VenvPath is null && !Design.IsDesignMode))
+        {
+            return;
+        }
+
+        if (value.PipShowResult is not null || value.IsLoading)
+        {
+            return;
+        }
+
+        var cts = new CancellationTokenSource();
+        extraInfoCts = cts;
+
+        LoadExtraInfoAsync(value, cts.Token)
+            .SafeFireAndForget(ex =>
+                logger.LogWarning(ex, "Failed to load details for Python package {Name}", value.Package.Name)
+            );
+    }
+
+    private async Task LoadExtraInfoAsync(
+        PythonPackagesItemViewModel item,
+        CancellationToken cancellationToken
+    )
+    {
+        try
+        {
+            await extraInfoLock.WaitAsync(cancellationToken);
+        }
+        catch (OperationCanceledException)
         {
             return;
         }
 
-        if (value.PipShowResult is null)
+        try
+        {
+            if (!ReferenceEquals(SelectedPackage, item) || item.PipShowResult is not null)
+            {
+                return;
+            }
+
+            await item.LoadExtraInfo(CreateVenvRunnerAsync);
+        }
+        finally
         {
-            value.LoadExtraInfo(VenvPath!, pyBaseInstall!).SafeFireAndForget();
+            extraInfoLock.Release();
         }
     }
 

StabilityMatrix.Core/Python/PipIndexResult.cs

@@ -10,14 +10,20 @@ public partial record PipIndexResult
 
     public static PipIndexResult Parse(string output)
     {
-        var match = AvailableVersionsRegex().Matches(output);
-
-        var versions = output
+        var versionsMatch = output
             .SplitLines()
             .Select(line => AvailableVersionsRegex().Match(line))
-            .First(m => m.Success)
-            .Groups["versions"].Value
-            .Split(
+            .FirstOrDefault(m => m.Success);
+
+        // Output without an "Available versions:" line (e.g. only warnings) has no versions to offer
+        if (versionsMatch is null)
+        {
+            return new PipIndexResult { AvailableVersions = [] };
+        }
+
+        var versions = versionsMatch
+            .Groups["versions"]
+            .Value.Split(
                 new[] { ',' },
                 StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries
             )

StabilityMatrix.Core/Python/PipShowResult.cs

@@ -37,12 +37,15 @@ public static PipShowResult Parse(string output)
         var indexOfLicense = GetIndexBySubstring(lines, "License:");
         var indexOfLocation = GetIndexBySubstring(lines, "Location:");
 
-        var licenseText =
-            indexOfLicense == -1 ? null : string.Join('\n', lines[indexOfLicense..indexOfLocation]);
+        // A multi-line license runs up to the "Location:" line. If that line is missing or comes
+        // first, only take the "License:" line itself.
+        var licenseEnd = indexOfLocation > indexOfLicense ? indexOfLocation : indexOfLicense + 1;
+
+        var licenseText = indexOfLicense == -1 ? null : string.Join('\n', lines[indexOfLicense..licenseEnd]);
 
         if (indexOfLicense != -1)
         {
-            lines.RemoveRange(indexOfLicense, indexOfLocation - indexOfLicense);
+            lines.RemoveRange(indexOfLicense, licenseEnd - indexOfLicense);
         }
 
         var linesDict = new Dictionary<string, string>();

StabilityMatrix.Tests/Core/PipIndexResultTests.cs

@@ -0,0 +1,35 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using StabilityMatrix.Core.Python;
+
+namespace StabilityMatrix.Tests.Core;
+
+[TestClass]
+public class PipIndexResultTests
+{
+    [TestMethod]
+    public void Parse_ReadsAvailableVersions()
+    {
+        var output = """
+            jax (0.4.30)
+            Available versions: 0.4.30, 0.4.29, 0.4.28
+              INSTALLED: 0.4.26
+              LATEST:    0.4.30
+            """;
+
+        var result = PipIndexResult.Parse(output);
+
+        CollectionAssert.AreEqual(new[] { "0.4.30", "0.4.29", "0.4.28" }, result.AvailableVersions.ToArray());
+    }
+
+    [TestMethod]
+    public void Parse_WithoutAvailableVersionsLine_ReturnsNoVersions()
+    {
+        var output = """
+            WARNING: pip index is currently an experimental command. It may be removed/changed in a future release without prior warning.
+            """;
+
+        var result = PipIndexResult.Parse(output);
+
+        Assert.AreEqual(0, result.AvailableVersions.Count);
+    }
+}

StabilityMatrix.Tests/Core/PipShowResultsTests.cs

@@ -181,4 +181,40 @@ public void TestEmptyInputThrowsFormatException()
         var input = "";
         Assert.ThrowsException<FormatException>(() => PipShowResult.Parse(input));
     }
+
+    [TestMethod]
+    public void TestLicenseWithoutLocation()
+    {
+        var input = """
+            Name: package-a
+            Version: 1.0.0
+            License: MIT
+            Requires: numpy
+            """;
+
+        var result = PipShowResult.Parse(input);
+
+        Assert.AreEqual("package-a", result.Name);
+        Assert.AreEqual("License: MIT", result.License);
+        Assert.IsNull(result.Location);
+        CollectionAssert.AreEqual(new[] { "numpy" }, result.Requires);
+    }
+
+    [TestMethod]
+    public void TestLocationBeforeLicense()
+    {
+        var input = """
+            Name: package-a
+            Version: 1.0.0
+            Location: /path/to/package
+            License: MIT
+            Requires: numpy
+            """;
+
+        var result = PipShowResult.Parse(input);
+
+        Assert.AreEqual("License: MIT", result.License);
+        Assert.AreEqual("/path/to/package", result.Location);
+        CollectionAssert.AreEqual(new[] { "numpy" }, result.Requires);
+    }
 }