🐛 Fix plugin dependency loading using AssemblyLoadContext (#35)

Author: Copilot

src/Blake.BuildTools/Blake.BuildTools.csproj

@@ -54,6 +54,7 @@
     <!-- Set InternalVisibleTo to allow access to internal members for testing -->
     <ItemGroup>
       <InternalsVisibleTo Include="Blake.CLI" />
+      <InternalsVisibleTo Include="Blake.BuildTools.Tests" />
     </ItemGroup>
 
 </Project>

src/Blake.BuildTools/Utils/PluginLoadContext.cs

@@ -0,0 +1,41 @@
+using System.Reflection;
+using System.Runtime.Loader;
+
+namespace Blake.BuildTools.Utils;
+
+/// <summary>
+/// A custom AssemblyLoadContext that provides isolated plugin loading with dependency resolution.
+/// Each plugin gets its own load context to avoid dependency conflicts.
+/// </summary>
+internal class PluginLoadContext : AssemblyLoadContext
+{
+    private readonly AssemblyDependencyResolver _resolver;
+
+    public PluginLoadContext(string pluginPath) : base(isCollectible: true)
+    {
+        _resolver = new AssemblyDependencyResolver(pluginPath);
+    }
+
+    protected override Assembly? Load(AssemblyName assemblyName)
+    {
+        string? assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
+        if (assemblyPath != null)
+        {
+            return LoadFromAssemblyPath(assemblyPath);
+        }
+
+        // Return null to fall back to default load context for shared dependencies
+        return null;
+    }
+
+    protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
+    {
+        string? libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
+        if (libraryPath != null)
+        {
+            return LoadUnmanagedDllFromPath(libraryPath);
+        }
+
+        return IntPtr.Zero;
+    }
+}

src/Blake.BuildTools/Utils/PluginLoader.cs

@@ -185,7 +185,11 @@ private static void LoadPluginDLLs(List<string> files, List<PluginContext> plugi
 
             try
             {
-                var assembly = Assembly.LoadFrom(file);
+                // Create a new load context for this plugin to resolve its dependencies
+                var loadContext = new PluginLoadContext(file);
+                var assemblyName = new AssemblyName(Path.GetFileNameWithoutExtension(file));
+                var assembly = loadContext.LoadFromAssemblyName(assemblyName);
+                
                 var pluginTypes = assembly.GetTypes()
                     .Where(t => typeof(IBlakePlugin).IsAssignableFrom(t) && !t.IsInterface && !t.IsAbstract);
 
@@ -199,7 +203,8 @@ private static void LoadPluginDLLs(List<string> files, List<PluginContext> plugi
             }
             catch (Exception ex)
             {
-                logger?.LogError("Error loading plugin from {file}", file, ex);
+                logger?.LogError("Error loading plugin from {file}: {message}", file, ex.Message);
+                logger?.LogDebug(ex, "Full error details for plugin {file}", file);
             }
         }
     }

tests/Blake.BuildTools.Tests/Utils/PluginLoaderTests.cs

@@ -0,0 +1,70 @@
+using Blake.BuildTools.Utils;
+using Microsoft.Extensions.Logging;
+using Xunit;
+
+namespace Blake.BuildTools.Tests.Utils;
+
+public class PluginLoaderTests
+{
+    [Fact]
+    public void LoadPluginDLLs_WithPluginWithDependencies_LoadsSuccessfully()
+    {
+        // Arrange
+        var logger = new TestLogger();
+        var pluginPath = Path.GetFullPath(Path.Combine(
+            Directory.GetCurrentDirectory(),
+            "..", "..", "..", "..", "..", "tests", "Blake.IntegrationTests", 
+            "TestPluginWithDependencies", "bin", "Debug", "net9.0", 
+            "BlakePlugin.TestPluginWithDependencies.dll"
+        ));
+
+        // Skip test if plugin doesn't exist (build not run)
+        if (!File.Exists(pluginPath))
+        {
+            Assert.True(true, "Plugin not built - skipping test");
+            return;
+        }
+
+        var files = new List<string> { pluginPath };
+        var plugins = new List<PluginContext>();
+
+        // Act & Assert - should not throw exception
+        var exception = Record.Exception(() =>
+        {
+            // Use reflection to call the private method
+            var method = typeof(PluginLoader).GetMethod("LoadPluginDLLs", 
+                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+            method?.Invoke(null, new object[] { files, plugins, logger });
+        });
+
+        // Assert
+        Assert.Null(exception);
+        Assert.Single(plugins);
+        Assert.Equal("BlakePlugin.TestPluginWithDependencies", plugins[0].PluginName);
+        
+        // Ensure no errors were logged
+        Assert.Empty(logger.ErrorMessages);
+    }
+
+    private class TestLogger : ILogger
+    {
+        public List<string> ErrorMessages { get; } = new List<string>();
+        public List<string> InfoMessages { get; } = new List<string>();
+
+        public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;
+        public bool IsEnabled(LogLevel logLevel) => true;
+
+        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+        {
+            var message = formatter(state, exception);
+            if (logLevel == LogLevel.Error)
+            {
+                ErrorMessages.Add(message);
+            }
+            else if (logLevel == LogLevel.Information)
+            {
+                InfoMessages.Add(message);
+            }
+        }
+    }
+}

tests/Blake.IntegrationTests/Commands/BlakePluginTests.cs

@@ -412,6 +412,70 @@ public async Task BlakeBake_WithoutProjectFile_SkipsPluginLoading()
         Assert.DoesNotContain("plugin", result.ErrorText, StringComparison.OrdinalIgnoreCase);
     }
 
+    [Fact]
+    public async Task BlakeBake_WithPluginWithDependencies_LoadsAndExecutesCorrectly()
+    {
+        // Arrange
+        var testDir = CreateTempDirectory("blake-plugins-with-deps");
+        var projectName = "PluginWithDepsTest";
+        
+        FileSystemHelper.CreateMinimalBlazorWasmProject(testDir, projectName);
+        
+        FileSystemHelper.CreateMarkdownFile(
+            Path.Combine(testDir, "Posts", "test.md"),
+            "Test Post",
+            "Content"
+        );
+
+        FileSystemHelper.CreateRazorTemplate(
+            Path.Combine(testDir, "Posts", "template.razor"),
+            @"@page ""/posts/{Slug}""
+<h1>@Model.Title</h1>
+<div>@((MarkupString)Html)</div>"
+        );
+
+        // Build the test plugin with dependencies first
+        var pluginWithDepsPath = Path.Combine(GetCurrentDirectory(), "tests", "Blake.IntegrationTests", "TestPluginWithDependencies");
+        var pluginBuildResult = await RunProcessAsync("dotnet", "build", pluginWithDepsPath);
+        Assert.Equal(0, pluginBuildResult.ExitCode);
+
+        // Add plugin project reference to the test project
+        var csprojPath = Path.Combine(testDir, $"{projectName}.csproj");
+        var csprojContent = File.ReadAllText(csprojPath);
+        
+        var pluginProjectPath = Path.Combine(pluginWithDepsPath, "BlakePlugin.TestPluginWithDependencies.csproj");
+        var relativePath = Path.GetRelativePath(testDir, pluginProjectPath);
+        
+        var updatedCsproj = csprojContent.Replace("</Project>", 
+            $@"  <ItemGroup>
+    <ProjectReference Include=""{relativePath}"" />
+  </ItemGroup>
+
+</Project>");
+        File.WriteAllText(csprojPath, updatedCsproj);
+
+        // Act
+        var result = await RunBlakeCommandAsync($"bake \"{testDir}\" --verbosity Debug");
+
+        // Assert
+        Assert.Equal(0, result.ExitCode);
+        
+        // Plugin should have created marker files with JSON serialization
+        FileSystemHelper.AssertFileExists(Path.Combine(testDir, ".plugin-with-deps-before-bake.txt"));
+        FileSystemHelper.AssertFileExists(Path.Combine(testDir, ".plugin-with-deps-after-bake.txt"));
+        
+        // Verify the JSON content was written correctly (meaning dependencies loaded)
+        var beforeContent = File.ReadAllText(Path.Combine(testDir, ".plugin-with-deps-before-bake.txt"));
+        var afterContent = File.ReadAllText(Path.Combine(testDir, ".plugin-with-deps-after-bake.txt"));
+        
+        Assert.Contains("Plugin with dependencies loaded successfully", beforeContent);
+        Assert.Contains("Plugin dependencies working in AfterBakeAsync", afterContent);
+        
+        // Should show plugin logs
+        Assert.Contains("TestPluginWithDependencies: BeforeBakeAsync called", result.OutputText);
+        Assert.Contains("TestPluginWithDependencies: AfterBakeAsync called", result.OutputText);
+    }
+
     private static string GetCurrentDirectory()
     {
         var currentDir = Directory.GetCurrentDirectory();

tests/Blake.IntegrationTests/TestPluginWithDependencies/BlakePlugin.TestPluginWithDependencies.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <EnableDynamicLoading>true</EnableDynamicLoading>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\src\Blake.BuildTools\Blake.BuildTools.csproj">
+      <Private>false</Private>
+      <ExcludeAssets>runtime</ExcludeAssets>
+    </ProjectReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
+</Project>

tests/Blake.IntegrationTests/TestPluginWithDependencies/TestPluginWithDependencies.cs

@@ -0,0 +1,39 @@
+using Blake.BuildTools;
+using Microsoft.Extensions.Logging;
+using Newtonsoft.Json;
+
+namespace BlakePlugin.TestPluginWithDependencies;
+
+public class TestPluginWithDependencies : IBlakePlugin
+{
+    public Task BeforeBakeAsync(BlakeContext context, ILogger? logger = null)
+    {
+        logger?.LogInformation("TestPluginWithDependencies: BeforeBakeAsync called");
+        
+        // Use Newtonsoft.Json to test dependency loading
+        var testObject = new { Message = "Plugin with dependencies loaded successfully", PageCount = context.MarkdownPages.Count };
+        var serialized = JsonConvert.SerializeObject(testObject);
+        
+        logger?.LogInformation("TestPluginWithDependencies: Serialized data: {SerializedData}", serialized);
+        
+        // Create a marker file to prove the plugin ran with dependencies
+        var testFilePath = Path.Combine(context.ProjectPath, ".plugin-with-deps-before-bake.txt");
+        File.WriteAllText(testFilePath, serialized);
+        
+        return Task.CompletedTask;
+    }
+
+    public Task AfterBakeAsync(BlakeContext context, ILogger? logger = null)
+    {
+        logger?.LogInformation("TestPluginWithDependencies: AfterBakeAsync called with {PageCount} generated pages", context.GeneratedPages.Count);
+        
+        // Use Newtonsoft.Json again to ensure dependency is still available
+        var testObject = new { Message = "Plugin dependencies working in AfterBakeAsync", GeneratedPageCount = context.GeneratedPages.Count };
+        var serialized = JsonConvert.SerializeObject(testObject);
+        
+        var testFilePath = Path.Combine(context.ProjectPath, ".plugin-with-deps-after-bake.txt");
+        File.WriteAllText(testFilePath, serialized);
+        
+        return Task.CompletedTask;
+    }
+}