[VS] Use current solution's project state to prevent any cache thrashing (#9121)

* Use current solution's project state to prevent any cache thrashing in FCS

* Update FSharpProjectOptionsManager.fs

* Update FSharpProjectOptionsManager.fs

vsintegration/src/FSharp.Editor/LanguageService/FSharpProjectOptionsManager.fs

@@ -240,8 +240,14 @@ type private FSharpProjectOptionsReactor (_workspace: VisualStudioWorkspace, set
                                 let! options = tryComputeOptionsByFile document ct
                                 reply.Reply options
                             else
-                                let! options = tryComputeOptions document.Project
-                                reply.Reply options
+                                // We only care about the latest project in the workspace's solution.
+                                // We do this to prevent any possible cache thrashing in FCS.
+                                let project = document.Project.Solution.Workspace.CurrentSolution.GetProject(document.Project.Id)
+                                if not (isNull project) then
+                                    let! options = tryComputeOptions project
+                                    reply.Reply options
+                                else
+                                    reply.Reply None
                         with
                         | _ ->
                             reply.Reply None
@@ -254,8 +260,14 @@ type private FSharpProjectOptionsReactor (_workspace: VisualStudioWorkspace, set
                             if project.Solution.Workspace.Kind = WorkspaceKind.MiscellaneousFiles || project.Name = FSharpConstants.FSharpMiscellaneousFilesName then
                                 reply.Reply None
                             else
-                                let! options = tryComputeOptions project
-                                reply.Reply options
+                                // We only care about the latest project in the workspace's solution.
+                                // We do this to prevent any possible cache thrashing in FCS.
+                                let project = project.Solution.Workspace.CurrentSolution.GetProject(project.Id)
+                                if not (isNull project) then
+                                    let! options = tryComputeOptions project
+                                    reply.Reply options
+                                else
+                                    reply.Reply None
                         with
                         | _ ->
                             reply.Reply None