From a4ad2fdd7d3693e92c21a868671b9c8d48dd0f85 Mon Sep 17 00:00:00 2001
From: Fred Kuipers <mr.fredk@gmail.com>
Date: Tue, 10 Aug 2021 00:44:14 -0400
Subject: [PATCH] Fixes to PluginManager for proper Notifier plugin handling

Addresses 2 issues:
1) If a single plugin class implemented both the Worker and Notifier interfaces, multiple instances of the class were created, meaning no shared state within the plugin. Now only 1 instance is created.
2) Plugins implementing only Notifier weren't properly loaded.
---
 .../PluginManagement/PluginManager.cs         | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/ObservatoryCore/PluginManagement/PluginManager.cs b/ObservatoryCore/PluginManagement/PluginManager.cs
index cc3e9c1..026df21 100644
--- a/ObservatoryCore/PluginManagement/PluginManager.cs
+++ b/ObservatoryCore/PluginManagement/PluginManager.cs
@@ -59,6 +59,15 @@ namespace Observatory.PluginManagement
                 LoadSettings(plugin);
                 plugin.Load(core);
             }
+            foreach (var plugin in notifyPlugins.Select(p => p.plugin))
+            {
+                // Notifiers which are also workers need not be loaded again (they are the same instance).
+                if (!plugin.GetType().IsAssignableTo(typeof(IObservatoryWorker)))
+                {
+                    LoadSettings(plugin);
+                    plugin.Load(core);
+                }
+            }
 
             core.Notification += pluginHandler.OnNotificationEvent;
         }
@@ -228,10 +237,18 @@ namespace Observatory.PluginManagement
                 ConstructorInfo constructor = worker.GetConstructor(Array.Empty<Type>());
                 object instance = constructor.Invoke(Array.Empty<object>());
                 workers.Add((instance as IObservatoryWorker, PluginStatus.Signed));
+                if (instance is IObservatoryNotifier)
+                {
+                    // This is also a notifier; add to the notifier list as well, so the work and notifier are
+                    // the same instance and can share state.
+                    notifiers.Add((instance as IObservatoryNotifier, PluginStatus.Signed));
+                }
                 pluginCount++;
             }
 
-            var notifyTypes = types.Where(t => t.IsAssignableTo(typeof(IObservatoryNotifier)));
+            // Filter out items which are also workers as we've already created them above.
+            var notifyTypes = types.Where(t =>
+                    t.IsAssignableTo(typeof(IObservatoryNotifier)) && !t.IsAssignableTo(typeof(IObservatoryWorker)));
             foreach (var notifier in notifyTypes)
             {
                 ConstructorInfo constructor = notifier.GetConstructor(Array.Empty<Type>());