Fixed IdGenerator creating new ids for reloaded assemblies

RGB.NET.Core/Ids/IdGenerator.cs

@@ -13,8 +13,10 @@ public static class IdGenerator
 
     // ReSharper disable InconsistentNaming
     private static readonly HashSet<string> _registeredIds = [];
-    private static readonly Dictionary<Assembly, Dictionary<string, string>> _idMappings = [];
-    private static readonly Dictionary<Assembly, Dictionary<string, int>> _counter = [];
+    // Keyed by the assembly's full name rather than the Assembly instance, so a reloaded copy of an assembly
+    // (e.g. a plugin in a new AssemblyLoadContext) keeps its ids and unloaded assemblies aren't kept alive.
+    private static readonly Dictionary<string, Dictionary<string, string>> _idMappings = [];
+    private static readonly Dictionary<string, Dictionary<string, int>> _counter = [];
     // ReSharper restore InconsistentNaming
 
     #endregion
@@ -31,13 +33,14 @@ public static class IdGenerator
 
     internal static string MakeUnique(Assembly callingAssembly, string id)
     {
-        if (!_idMappings.TryGetValue(callingAssembly, out Dictionary<string, string>? idMapping))
+        string assemblyKey = GetAssemblyKey(callingAssembly);
+        if (!_idMappings.TryGetValue(assemblyKey, out Dictionary<string, string>? idMapping))
         {
-            _idMappings.Add(callingAssembly, idMapping = []);
-            _counter.Add(callingAssembly, []);
+            _idMappings.Add(assemblyKey, idMapping = []);
+            _counter.Add(assemblyKey, []);
         }
 
-        Dictionary<string, int> counterMapping = _counter[callingAssembly];
+        Dictionary<string, int> counterMapping = _counter[assemblyKey];
 
         if (!idMapping.TryGetValue(id, out string? mappedId))
         {
@@ -65,9 +68,11 @@ internal static string MakeUnique(Assembly callingAssembly, string id)
 
     internal static void ResetCounter(Assembly callingAssembly)
     {
-        if (_counter.TryGetValue(callingAssembly, out Dictionary<string, int>? counter))
+        if (_counter.TryGetValue(GetAssemblyKey(callingAssembly), out Dictionary<string, int>? counter))
             counter.Clear();
     }
 
+    private static string GetAssemblyKey(Assembly assembly) => assembly.FullName ?? assembly.GetName().Name ?? string.Empty;
+
     #endregion
 }

Tests/RGB.NET.Core.Tests/Ids/IdGeneratorTest.cs

@@ -0,0 +1,66 @@
+using System;
+using System.IO;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.Loader;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace RGB.NET.Core.Tests.Ids;
+
+[TestClass]
+public class IdGeneratorTest
+{
+    #region Helper
+
+    // Called through reflection from a reloaded copy of this assembly, so that copy is the calling assembly
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    public static string MakeUniqueAndReset(string id)
+    {
+        string uniqueId = IdGenerator.MakeUnique(id);
+        IdGenerator.ResetCounter();
+        return uniqueId;
+    }
+
+    private static string MakeUniqueFromReloadedAssembly(string id)
+    {
+        AssemblyLoadContext context = new(nameof(IdGeneratorTest), true);
+        try
+        {
+            using MemoryStream stream = new(File.ReadAllBytes(typeof(IdGeneratorTest).Assembly.Location));
+            Assembly assembly = context.LoadFromStream(stream);
+            MethodInfo method = assembly.GetType(typeof(IdGeneratorTest).FullName!)!.GetMethod(nameof(MakeUniqueAndReset))!;
+            return (string)method.Invoke(null, [id])!;
+        }
+        finally
+        {
+            context.Unload();
+        }
+    }
+
+    #endregion
+
+    #region Tests
+
+    [TestMethod]
+    public void ReloadedAssemblyGetsTheSameIdAfterReset()
+    {
+        string id = $"Manufacturer Model {Guid.NewGuid()}";
+
+        string firstLoad = MakeUniqueFromReloadedAssembly(id);
+        string secondLoad = MakeUniqueFromReloadedAssembly(id);
+
+        Assert.AreEqual(id, firstLoad);
+        Assert.AreEqual(firstLoad, secondLoad);
+    }
+
+    [TestMethod]
+    public void DuplicateIdsWithinAnAssemblyAreStillUnique()
+    {
+        string id = $"Manufacturer Model {Guid.NewGuid()}";
+
+        Assert.AreEqual(id, IdGenerator.MakeUnique(id));
+        Assert.AreEqual($"{id} (2)", IdGenerator.MakeUnique(id));
+    }
+
+    #endregion
+}