Fix leak in _hostAnalyzerStateMap

Fixes [AB#1449967](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1449967)

dotnet#57648 fixed a race condition in computing the host analyzer references, but introduced a leak in _hostAnalyzerStateMap, wherein each new solution opened ends up creating a new entry in this map, even though the underlying set of host analyzer references doesn't change. This is due to the fact that each new SolutionState instance creates a new instance of HostDiagnosticAnalyzers, whose constructor creates a new map from analyzer references ID to the analyzer reference. This map is used as part of the key for _hostAnalyzerStateMap, leading to the leak.

This change fixes the leak by using the underlying list of host analyzer references as part of the key for _hostAnalyzerStateMap, which is reference equals across all solution instances opened in the VS session. Verified manually that after this fix, repeatedly opening and closing a solution in VS no longer leads to unbounded growth of _hostAnalyzerStateMap.

src/EditorFeatures/Test2/Diagnostics/DiagnosticServiceTests.vb

@@ -149,8 +149,7 @@ Namespace Microsoft.CodeAnalysis.Editor.Implementation.Diagnostics.UnitTests
                 Assert.Equal(workspaceDiagnosticAnalyzer.DiagDescriptor.Id, descriptors(0).Id)
 
                 ' Add an existing workspace analyzer to the project, ensure no duplicate diagnostics.
-                Dim duplicateProjectAnalyzersReference = hostAnalyzers.GetHostAnalyzerReferencesMap().First().Value
-                project = project.WithAnalyzerReferences({duplicateProjectAnalyzersReference})
+                project = project.WithAnalyzerReferences(hostAnalyzers.HostAnalyzerReferences)
 
                 ' Verify duplicate descriptors or diagnostics.
                 descriptorsMap = hostAnalyzers.GetDiagnosticDescriptorsPerReference(diagnosticService.AnalyzerInfoCache, project)

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.HostStates.cs

@@ -16,10 +16,10 @@ private partial class StateManager
         {
             public IEnumerable<StateSet> GetAllHostStateSets()
             {
-                var analyzerReferencesMap = _workspace.CurrentSolution.State.Analyzers.GetHostAnalyzerReferencesMap();
+                var analyzerReferences = _workspace.CurrentSolution.State.Analyzers.HostAnalyzerReferences;
                 foreach (var (key, value) in _hostAnalyzerStateMap)
                 {
-                    if (key.AnalyzerReferences == analyzerReferencesMap)
+                    if (key.AnalyzerReferences == analyzerReferences)
                     {
                         foreach (var stateSet in value.OrderedStateSets)
                         {
@@ -31,7 +31,7 @@ public IEnumerable<StateSet> GetAllHostStateSets()
 
             private HostAnalyzerStateSets GetOrCreateHostStateSets(Project project, ProjectAnalyzerStateSets projectStateSets)
             {
-                var key = new HostAnalyzerStateSetKey(project.Language, project.Solution.State.Analyzers.GetHostAnalyzerReferencesMap());
+                var key = new HostAnalyzerStateSetKey(project.Language, project.Solution.State.Analyzers.HostAnalyzerReferences);
                 var hostStateSets = ImmutableInterlocked.GetOrAdd(ref _hostAnalyzerStateMap, key, CreateLanguageSpecificAnalyzerMap, project.Solution.State.Analyzers);
                 return hostStateSets.WithExcludedAnalyzers(projectStateSets.SkippedAnalyzersInfo.SkippedAnalyzers);
 

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.StateManager.cs

@@ -314,14 +314,14 @@ private void VerifyProjectDiagnosticStates(IEnumerable<StateSet> stateSets)
 
             private readonly struct HostAnalyzerStateSetKey : IEquatable<HostAnalyzerStateSetKey>
             {
-                public HostAnalyzerStateSetKey(string language, ImmutableDictionary<object, AnalyzerReference> analyzerReferences)
+                public HostAnalyzerStateSetKey(string language, IReadOnlyList<AnalyzerReference> analyzerReferences)
                 {
                     Language = language;
                     AnalyzerReferences = analyzerReferences;
                 }
 
                 public string Language { get; }
-                public ImmutableDictionary<object, AnalyzerReference> AnalyzerReferences { get; }
+                public IReadOnlyList<AnalyzerReference> AnalyzerReferences { get; }
 
                 public bool Equals(HostAnalyzerStateSetKey other)
                     => Language == other.Language && AnalyzerReferences == other.AnalyzerReferences;

src/Workspaces/Core/Portable/Diagnostics/HostDiagnosticAnalyzers.cs

@@ -53,8 +53,9 @@ internal sealed class HostDiagnosticAnalyzers
         /// </remarks>
         private readonly ConditionalWeakTable<IReadOnlyList<AnalyzerReference>, StrongBox<ImmutableDictionary<string, SkippedHostAnalyzersInfo>>> _skippedHostAnalyzers;
 
-        internal HostDiagnosticAnalyzers(IEnumerable<AnalyzerReference> hostAnalyzerReferences)
+        internal HostDiagnosticAnalyzers(IReadOnlyList<AnalyzerReference> hostAnalyzerReferences)
         {
+            HostAnalyzerReferences = hostAnalyzerReferences;
             _hostAnalyzerReferencesMap = CreateAnalyzerReferencesMap(hostAnalyzerReferences);
             _hostDiagnosticAnalyzersPerLanguageMap = new ConcurrentDictionary<string, ImmutableDictionary<object, ImmutableArray<DiagnosticAnalyzer>>>(concurrencyLevel: 2, capacity: 2);
             _lazyHostDiagnosticAnalyzersPerReferenceMap = new Lazy<ImmutableDictionary<object, ImmutableArray<DiagnosticAnalyzer>>>(() => CreateDiagnosticAnalyzersPerReferenceMap(_hostAnalyzerReferencesMap), isThreadSafe: true);
@@ -64,10 +65,9 @@ internal HostDiagnosticAnalyzers(IEnumerable<AnalyzerReference> hostAnalyzerRefe
         }
 
         /// <summary>
-        /// It returns a map with <see cref="AnalyzerReference.Id"/> as key and <see cref="AnalyzerReference"/> as value
+        /// List of host <see cref="AnalyzerReference"/>s
         /// </summary>
-        public ImmutableDictionary<object, AnalyzerReference> GetHostAnalyzerReferencesMap()
-            => _hostAnalyzerReferencesMap;
+        public IReadOnlyList<AnalyzerReference> HostAnalyzerReferences { get; }
 
         /// <summary>
         /// Get <see cref="AnalyzerReference"/> identity and <see cref="DiagnosticAnalyzer"/>s map for given <paramref name="language"/>