Add functions to get a plugin by assembly

This is intended for advanced IPC scenarios, for example, accepting
a delegate or an object and identifying which plugin it originates
from, in order to display integration information to the user, and/or
to release references when the originating plugin is unloaded/reloaded
if it forgot to clean after itself.

Dalamud/Plugin/DalamudPluginInterface.cs

@@ -5,6 +5,7 @@ using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.Loader;
 using System.Threading.Tasks;
 
 using Dalamud.Configuration;
@@ -269,6 +270,30 @@ internal sealed class DalamudPluginInterface : IDalamudPluginInterface, IDisposa
         return true;
     }
 
+    /// <summary>
+    /// Gets the plugin the given assembly is part of.
+    /// </summary>
+    /// <param name="assembly">The assembly to check.</param>
+    /// <returns>The plugin the given assembly is part of, or null if this is a shared assembly or if this information cannot be determined.</returns>
+    public IExposedPlugin? GetPlugin(Assembly assembly)
+        => AssemblyLoadContext.GetLoadContext(assembly) switch
+        {
+            null => null,
+            var context => this.GetPlugin(context),
+        };
+
+    /// <summary>
+    /// Gets the plugin that loads in the given context.
+    /// </summary>
+    /// <param name="context">The context to check.</param>
+    /// <returns>The plugin that loads in the given context, or null if this isn't a plugin's context or if this information cannot be determined.</returns>
+    public IExposedPlugin? GetPlugin(AssemblyLoadContext context)
+        => Service<PluginManager>.Get().InstalledPlugins.FirstOrDefault(p => p.LoadsIn(context)) switch
+        {
+            null => null,
+            var p => new ExposedPlugin(p),
+        };
+
     #region IPC
 
     /// <inheritdoc cref="DataShare.GetOrCreateData{T}"/>

Dalamud/Plugin/IDalamudPluginInterface.cs

@@ -1,6 +1,8 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
+using System.Reflection;
+using System.Runtime.Loader;
 using System.Threading.Tasks;
 
 using Dalamud.Configuration;
@@ -180,6 +182,20 @@ public interface IDalamudPluginInterface
     /// <returns>Returns false if the DalamudInterface was null.</returns>
     bool OpenDeveloperMenu();
 
+    /// <summary>
+    /// Gets the plugin the given assembly is part of.
+    /// </summary>
+    /// <param name="assembly">The assembly to check.</param>
+    /// <returns>The plugin the given assembly is part of, or null if this is a shared assembly or if this information cannot be determined.</returns>
+    IExposedPlugin? GetPlugin(Assembly assembly);
+
+    /// <summary>
+    /// Gets the plugin that loads in the given context.
+    /// </summary>
+    /// <param name="context">The context to check.</param>
+    /// <returns>The plugin that loads in the given context, or null if this isn't a plugin's context or if this information cannot be determined.</returns>
+    IExposedPlugin? GetPlugin(AssemblyLoadContext context);
+
     /// <inheritdoc cref="DataShare.GetOrCreateData{T}"/>
     T GetOrCreateData<T>(string tag, Func<T> dataGenerator) where T : class;
 

Dalamud/Plugin/Internal/Types/LocalPlugin.cs

@@ -3,6 +3,7 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.ExceptionServices;
+using System.Runtime.Loader;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -553,6 +554,14 @@ internal class LocalPlugin : IAsyncDisposable
         });
     }
 
+    /// <summary>
+    /// Checks whether this plugin loads in the given load context.
+    /// </summary>
+    /// <param name="context">The load context to check.</param>
+    /// <returns>Whether this plugin loads in the given load context.</returns>
+    public bool LoadsIn(AssemblyLoadContext context)
+        => this.loader?.LoadContext == context;
+
     /// <summary>
     /// Save this plugin manifest.
     /// </summary>