Revert "When we're removing the last project, fire SolutionRemoved"

src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProject.cs

@@ -1231,17 +1231,7 @@ public void RemoveFromWorkspace()
                 // references being converted to metadata references (or vice versa) and we might either
                 // miss stopping a file watcher or might end up double-stopping a file watcher.
                 remainingMetadataReferences = w.CurrentSolution.GetRequiredProject(Id).MetadataReferences;
-                _workspace.RemoveProjectFromTrackingMaps_NoLock(Id);
-
-                // If this is our last project, clear the entire solution.
-                if (w.CurrentSolution.ProjectIds.Count == 1)
-                {
-                    _workspace.RemoveSolution_NoLock();
-                }
-                else
-                {
-                    _workspace.OnProjectRemoved(Id);
-                }
+                w.OnProjectRemoved(Id);
             });
 
             Contract.ThrowIfNull(remainingMetadataReferences);

src/VisualStudio/Core/Def/ProjectSystem/VisualStudioProjectFactory.cs

@@ -11,7 +11,6 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Editor.Shared.Utilities;
-using Microsoft.CodeAnalysis.ExternalAccess.VSTypeScript.Api;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.Host.Mef;
 using Microsoft.VisualStudio.LanguageServices.ExternalAccess.VSTypeScript.Api;
@@ -116,7 +115,6 @@ await _visualStudioWorkspaceImpl.ApplyChangeToWorkspaceAsync(w =>
                     .WithTelemetryId(creationInfo.ProjectGuid);
 
                 // If we don't have any projects and this is our first project being added, then we'll create a new SolutionId
-                // and count this as the solution being added so that event is raised.
                 if (w.CurrentSolution.ProjectIds.Count == 0)
                 {
                     var solutionSessionId = GetSolutionSessionId();

src/VisualStudio/Core/Def/ProjectSystem/VisualStudioWorkspaceImpl.cs

@@ -1660,11 +1660,7 @@ private ProjectReferenceInformation GetReferenceInfo_NoLock(ProjectId projectId)
             return _projectReferenceInfoMap.GetOrAdd(projectId, _ => new ProjectReferenceInformation());
         }
 
-        /// <summary>
-        /// Removes the project from the various maps this type maintains; it's still up to the caller to actually remove
-        /// the project in one way or another.
-        /// </summary>
-        internal void RemoveProjectFromTrackingMaps_NoLock(ProjectId projectId)
+        protected internal override void OnProjectRemoved(ProjectId projectId)
         {
             string? languageName;
 
@@ -1708,6 +1704,8 @@ internal void RemoveProjectFromTrackingMaps_NoLock(ProjectId projectId)
                 }
             }
 
+            base.OnProjectRemoved(projectId);
+
             // Try to update the UI context info.  But cancel that work if we're shutting down.
             _threadingContext.RunWithShutdownBlockAsync(async cancellationToken =>
             {
@@ -1716,31 +1714,6 @@ internal void RemoveProjectFromTrackingMaps_NoLock(ProjectId projectId)
             });
         }
 
-        internal void RemoveSolution_NoLock()
-        {
-            Contract.ThrowIfFalse(_gate.CurrentCount == 0);
-
-            // At this point, we should have had RemoveProjectFromTrackingMaps_NoLock called for everything else, so it's just the solution itself
-            // to clean up
-            Contract.ThrowIfFalse(_projectReferenceInfoMap.Count == 0);
-            Contract.ThrowIfFalse(_projectToHierarchyMap.Count == 0);
-            Contract.ThrowIfFalse(_projectToGuidMap.Count == 0);
-            Contract.ThrowIfFalse(_projectToMaxSupportedLangVersionMap.Count == 0);
-            Contract.ThrowIfFalse(_projectToDependencyNodeTargetIdentifier.Count == 0);
-            Contract.ThrowIfFalse(_projectToRuleSetFilePath.Count == 0);
-            Contract.ThrowIfFalse(_projectSystemNameToProjectsMap.Count == 0);
-
-            // Create a new empty solution and set this; we will reuse the same SolutionId and path since components still may have persistence information they still need
-            // to look up by that location; we also keep the existing analyzer references around since those are host-level analyzers that were loaded asynchronously.
-            SetCurrentSolution(
-                solution => CreateSolution(
-                    SolutionInfo.Create(
-                        SolutionId.CreateNewId(),
-                        VersionStamp.Create(),
-                        analyzerReferences: solution.AnalyzerReferences)),
-                WorkspaceChangeKind.SolutionRemoved);
-        }
-
         private sealed class ProjectReferenceInformation
         {
             public readonly List<string> OutputPaths = new();

src/VisualStudio/Core/Test/ProjectSystemShim/VisualStudioProjectTests/WorkspaceChangedEventTests.vb

@@ -106,21 +106,5 @@ Namespace Microsoft.VisualStudio.LanguageServices.UnitTests.ProjectSystemShim
                 Assert.Same(startingSolution, environment.Workspace.CurrentSolution)
             End Using
         End Function
-
-        <WpfFact>
-        <CombinatorialData>
-        Public Async Function AddingAndRemovingOnlyProjectTriggersSolutionAddedAndSolutionRemoved() As Task
-            Using environment = New TestEnvironment()
-                Dim workspaceChangeEvents = New WorkspaceChangeWatcher(environment)
-                Dim project = Await environment.ProjectFactory.CreateAndAddToWorkspaceAsync(
-                    "Project", LanguageNames.CSharp, CancellationToken.None)
-
-                Assert.Equal(WorkspaceChangeKind.SolutionAdded, Assert.Single(Await workspaceChangeEvents.GetNewChangeEventsAsync()).Kind)
-
-                project.RemoveFromWorkspace()
-
-                Assert.Equal(WorkspaceChangeKind.SolutionRemoved, Assert.Single(Await workspaceChangeEvents.GetNewChangeEventsAsync()).Kind)
-            End Using
-        End Function
     End Class
 End Namespace

src/VisualStudio/IntegrationTest/New.IntegrationTests/CSharp/CSharpFindReferences.cs

@@ -164,9 +164,9 @@ public async Task VerifyWorkingFolder()
 
             await TestServices.SolutionExplorer.CloseSolutionAsync(HangMitigatingCancellationToken);
 
-            // Since we no longer have an open solution, we don't have a storage location for it, since that
-            // depends on the open solution.
-            Assert.Null(persistentStorageConfiguration.TryGetStorageLocation(SolutionKey.ToSolutionKey(visualStudioWorkspace.CurrentSolution)));
+            // because the solution cache directory is stored in the user temp folder, 
+            // closing the solution has no effect on what is returned.
+            Assert.NotNull(persistentStorageConfiguration.TryGetStorageLocation(SolutionKey.ToSolutionKey(visualStudioWorkspace.CurrentSolution)));
         }
 
         private async Task WaitForNavigateAsync(CancellationToken cancellationToken)