Add static plugin initializer, add tree builder and tree node builder

Remora.Plugins.Abstractions/Attributes/RemoraPlugin.cs

@@ -31,19 +31,4 @@ namespace Remora.Plugins.Abstractions.Attributes;
 /// </summary>
 [PublicAPI]
 [AttributeUsage(AttributeTargets.Assembly)]
-public sealed class RemoraPlugin : Attribute
-{
-    /// <summary>
-    /// Gets the plugin descriptor that the assembly exports.
-    /// </summary>
-    public Type PluginDescriptor { get; }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="RemoraPlugin"/> class.
-    /// </summary>
-    /// <param name="pluginDescriptor">The descriptor type.</param>
-    public RemoraPlugin(Type pluginDescriptor)
-    {
-        this.PluginDescriptor = pluginDescriptor;
-    }
-}
+public sealed class RemoraPlugin : Attribute;

Remora.Plugins.Abstractions/IMigratablePlugin.cs

@@ -37,8 +37,7 @@ public interface IMigratablePlugin : IPluginDescriptor
     /// <summary>
     /// Performs any migrations required by the plugin.
     /// </summary>
-    /// <param name="serviceProvider">The available services.</param>
     /// <param name="ct">The cancellation token for this operation.</param>
     /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
-    Task<Result> MigrateAsync(IServiceProvider serviceProvider, CancellationToken ct = default);
+    Task<Result> MigrateAsync(CancellationToken ct = default);
 }

Remora.Plugins.Abstractions/IPluginDescriptor.cs

@@ -21,6 +21,7 @@
 //
 
 using System;
+using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
@@ -48,20 +49,22 @@ public interface IPluginDescriptor
     /// <summary>
     /// Gets the version of the plugin.
     /// </summary>
-    Version Version { get; }
+    Version Version => Assembly.GetAssembly(GetType())?.GetName().Version ?? new Version(1, 0, 0);
 
     /// <summary>
     /// Configures services provided by the plugin in the application's service collection.
     /// </summary>
     /// <param name="serviceCollection">The service collection.</param>
     /// <returns>A result that may or may not have succeeded.</returns>
-    Result ConfigureServices(IServiceCollection serviceCollection);
+    static virtual IServiceCollection ConfigureServices(IServiceCollection serviceCollection) => serviceCollection;
 
     /// <summary>
     /// Performs any post-registration initialization required by the plugin.
     /// </summary>
-    /// <param name="serviceProvider">The service provider.</param>
     /// <param name="ct">The cancellation token for this operation.</param>
     /// <returns>A result that may or may not have succeeded.</returns>
-    ValueTask<Result> InitializeAsync(IServiceProvider serviceProvider, CancellationToken ct = default);
+    ValueTask<Result> InitializeAsync(CancellationToken ct = default);
+
+    /// <inheritdoc cref="object.ToString"/>
+    string ToString() => this.Name;
 }

Remora.Plugins.Abstractions/Remora.Plugins.Abstractions.csproj

@@ -1,6 +1,8 @@
 <Project Sdk="Remora.Sdk">
     <PropertyGroup>
         <VersionPrefix>5.0.1</VersionPrefix>
+		<TargetNetStandard>false</TargetNetStandard>
+		<LibraryFrameworks>net8.0;net9.0</LibraryFrameworks>
         <Description>
             Abstract representations of a plugin system.
         </Description>

Remora.Plugins/PluginTree.cs

@@ -27,7 +27,6 @@
 using System.Threading;
 using System.Threading.Tasks;
 using JetBrains.Annotations;
-using Microsoft.Extensions.DependencyInjection;
 using Remora.Plugins.Abstractions;
 using Remora.Plugins.Errors;
 using Remora.Results;
@@ -37,55 +36,27 @@ namespace Remora.Plugins;
 /// <summary>
 /// Represents a tree of plugins, ordered by their dependencies.
 /// </summary>
+/// <remarks>
+/// Initializes a new instance of the <see cref="PluginTree"/> class.
+/// </remarks>
+/// <param name="branches">The dependency branches.</param>
 [PublicAPI]
-public sealed class PluginTree
+public sealed class PluginTree(List<PluginTreeNode>? branches = null)
 {
-    private readonly List<PluginTreeNode> _branches;
+    private readonly List<PluginTreeNode> _branches = branches ?? [];
 
     /// <summary>
     /// Gets the root nodes of the identified plugin dependency branches. The root node is considered to be the
     /// application itself, which is implicitly initialized.
     /// </summary>
     public IReadOnlyCollection<PluginTreeNode> Branches => _branches;
 
-    /// <summary>
-    /// Initializes a new instance of the <see cref="PluginTree"/> class.
-    /// </summary>
-    /// <param name="branches">The dependency branches.</param>
-    public PluginTree(List<PluginTreeNode>? branches = null)
-    {
-        _branches = branches ?? new List<PluginTreeNode>();
-    }
-
-    /// <summary>
-    /// Configures the services required by the plugins.
-    /// </summary>
-    /// <param name="serviceCollection">The service collection to configure.</param>
-    /// <returns>A result which may or may not have succeeded.</returns>
-    public Result ConfigureServices(IServiceCollection serviceCollection)
-    {
-        var results = Walk
-        (
-            node => new PluginConfigurationFailed
-            (
-                node.Plugin,
-                "One or more of the plugin's dependencies failed to configure their services."
-            ),
-            node => node.Plugin.ConfigureServices(serviceCollection)
-        ).ToList();
-
-        return results.Any(r => !r.IsSuccess)
-            ? new AggregateError(results.Where(r => !r.IsSuccess).Cast<IResult>().ToList())
-            : Result.FromSuccess();
-    }
-
     /// <summary>
     /// Initializes the plugins in the tree.
     /// </summary>
-    /// <param name="services">The available services.</param>
     /// <param name="ct">The cancellation token for this operation.</param>
     /// <returns>A result which may or may not have succeeded.</returns>
-    public async Task<Result> InitializeAsync(IServiceProvider services, CancellationToken ct = default)
+    public async Task<Result> InitializeAsync(CancellationToken ct = default)
     {
         var results = await WalkAsync
         (
@@ -94,7 +65,7 @@ public async Task<Result> InitializeAsync(IServiceProvider services, Cancellatio
                 node.Plugin,
                 "One or more of the plugin's dependencies failed to initialize."
             ),
-            async (node, c) => await node.Plugin.InitializeAsync(services, c),
+            async (node, c) => await node.Plugin.InitializeAsync(c),
             ct: ct
         ).ToListAsync(ct);
 
@@ -106,10 +77,9 @@ public async Task<Result> InitializeAsync(IServiceProvider services, Cancellatio
     /// <summary>
     /// Migrates any persistent data stores of the plugins in the tree.
     /// </summary>
-    /// <param name="services">The available services.</param>
     /// <param name="ct">The cancellation token for this operation.</param>
     /// <returns>A result which may or may not have succeeded.</returns>
-    public async Task<Result> MigrateAsync(IServiceProvider services, CancellationToken ct = default)
+    public async Task<Result> MigrateAsync(CancellationToken ct = default)
     {
         var results = await WalkAsync
         (
@@ -125,7 +95,7 @@ public async Task<Result> MigrateAsync(IServiceProvider services, CancellationTo
                     return Result.FromSuccess();
                 }
 
-                return await migratablePlugin.MigrateAsync(services, c);
+                return await migratablePlugin.MigrateAsync(c);
             },
             ct: ct
         ).ToListAsync(ct);

Remora.Plugins/PluginTreeBuilder.cs

@@ -0,0 +1,69 @@
+//
+//  PluginTreeBuilder.cs
+//
+//  Author:
+//       Jarl Gullberg <jarl.gullberg@gmail.com>
+//
+//  Copyright (c) Jarl Gullberg
+//
+//  This program is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU Lesser General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU Lesser General Public License for more details.
+//
+//  You should have received a copy of the GNU Lesser General Public License
+//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+using System;
+using System.Collections.Generic;
+using JetBrains.Annotations;
+using Remora.Plugins.Abstractions;
+
+namespace Remora.Plugins
+{
+    /// <summary>
+    /// A type that facilitates the creation of a <see cref="PluginTree"/>.
+    /// </summary>
+    /// <param name="filter">A filter predicate which determines if the plugin should be loaded.</param>
+    [PublicAPI]
+    public sealed class PluginTreeBuilder(Predicate<IPluginDescriptor> filter)
+    {
+        private readonly List<PluginTreeNodeBuilder> _treeNodeBuilders = [];
+
+        /// <summary>
+        /// Adds a tree node builder to the collection.
+        /// </summary>
+        /// <param name="node">The node to add.</param>
+        public void AddTreeNode(PluginTreeNodeBuilder node)
+        {
+            _treeNodeBuilders.Add(node);
+        }
+
+        /// <summary>
+        /// Builds the <see cref="PluginTree"/>.
+        /// </summary>
+        /// <param name="serviceProvider">The service provider.</param>
+        /// <returns>A new <see cref="PluginTree"/>.</returns>
+        [Pure]
+        [PublicAPI]
+        public PluginTree Build(IServiceProvider serviceProvider)
+        {
+            var tree = new PluginTree();
+            foreach (var node in _treeNodeBuilders)
+            {
+                var pluginTreeNode = node.Build(serviceProvider);
+                if (filter.Invoke(pluginTreeNode.Plugin))
+                {
+                    tree.AddBranch(pluginTreeNode);
+                }
+            }
+            return tree;
+        }
+    }
+}

Remora.Plugins/PluginTreeNode.cs

@@ -57,7 +57,7 @@ public PluginTreeNode
     )
     {
         this.Plugin = plugin;
-        _dependents = dependants ?? new List<PluginTreeNode>();
+        _dependents = dependants ?? [];
     }
 
     /// <summary>
@@ -94,6 +94,6 @@ public IEnumerable<PluginTreeNode> GetAllDependents()
     /// <inheritdoc/>
     public override string ToString()
     {
-        return $"{this.Plugin} => ({string.Join(", ", _dependents.Select(d => d.Plugin))})";
+        return $"{this.Plugin} => ({string.Join(", ", _dependents.Select(d => d.Plugin.ToString()))})";
     }
 }