Revert making in-memory cross-project references the only option

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

@@ -85,9 +85,13 @@ module private FSharpProjectOptionsHelpers =
                            let v2 = p2.GetDependentVersionAsync(ct).Result
                            v1 <> v2))
 
-    let inline isProjectInvalidated (oldProject: Project) (newProject: Project) ct =
-        hasProjectVersionChanged oldProject newProject
-        || hasDependentVersionChanged oldProject newProject ct
+    let isProjectInvalidated (oldProject: Project) (newProject: Project) ct =
+        let hasProjectVersionChanged = hasProjectVersionChanged oldProject newProject
+
+        if newProject.AreFSharpInMemoryCrossProjectReferencesEnabled then
+            hasProjectVersionChanged || hasDependentVersionChanged oldProject newProject ct
+        else
+            hasProjectVersionChanged
 
 [<RequireQualifiedAccess>]
 type private FSharpProjectOptionsMessage =
@@ -272,20 +276,21 @@ type private FSharpProjectOptionsReactor(checker: FSharpChecker) =
 
                 let referencedProjects = ResizeArray()
 
-                for projectReference in project.ProjectReferences do
-                    let referencedProject = project.Solution.GetProject(projectReference.ProjectId)
-
-                    if referencedProject.Language = FSharpConstants.FSharpLanguageName then
-                        match! tryComputeOptions referencedProject ct with
-                        | None -> canBail <- true
-                        | Some (_, projectOptions) ->
-                            referencedProjects.Add(
-                                FSharpReferencedProject.FSharpReference(referencedProject.OutputFilePath, projectOptions)
-                            )
-                    elif referencedProject.SupportsCompilation then
-                        let! comp = referencedProject.GetCompilationAsync(ct) |> Async.AwaitTask
-                        let peRef = createPEReference referencedProject comp
-                        referencedProjects.Add(peRef)
+                if project.AreFSharpInMemoryCrossProjectReferencesEnabled then
+                    for projectReference in project.ProjectReferences do
+                        let referencedProject = project.Solution.GetProject(projectReference.ProjectId)
+
+                        if referencedProject.Language = FSharpConstants.FSharpLanguageName then
+                            match! tryComputeOptions referencedProject ct with
+                            | None -> canBail <- true
+                            | Some (_, projectOptions) ->
+                                referencedProjects.Add(
+                                    FSharpReferencedProject.FSharpReference(referencedProject.OutputFilePath, projectOptions)
+                                )
+                        elif referencedProject.SupportsCompilation then
+                            let! comp = referencedProject.GetCompilationAsync(ct) |> Async.AwaitTask
+                            let peRef = createPEReference referencedProject comp
+                            referencedProjects.Add(peRef)
 
                 if canBail then
                     return None

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

@@ -116,6 +116,9 @@ type internal FSharpWorkspaceServiceFactory [<Composition.ImportingConstructor>]
 
                             let useSyntaxTreeCache = editorOptions.LanguageServicePerformance.UseSyntaxTreeCache
 
+                            let enableInMemoryCrossProjectReferences =
+                                editorOptions.LanguageServicePerformance.EnableInMemoryCrossProjectReferences
+
                             let enableFastFindReferences =
                                 editorOptions.LanguageServicePerformance.EnableFastFindReferencesAndRename
 
@@ -156,6 +159,7 @@ type internal FSharpWorkspaceServiceFactory [<Composition.ImportingConstructor>]
                                         nameof enableLiveBuffers, enableLiveBuffers
                                         nameof useSyntaxTreeCache, useSyntaxTreeCache
                                         nameof enableParallelReferenceResolution, enableParallelReferenceResolution
+                                        nameof enableInMemoryCrossProjectReferences, enableInMemoryCrossProjectReferences
                                         nameof enableFastFindReferences, enableFastFindReferences
                                         nameof isInlineParameterNameHintsEnabled, isInlineParameterNameHintsEnabled
                                         nameof isInlineTypeHintsEnabled, isInlineTypeHintsEnabled

vsintegration/src/FSharp.Editor/Options/EditorOptions.fs

@@ -78,6 +78,7 @@ type CodeFixesOptions =
 [<CLIMutable>]
 type LanguageServicePerformanceOptions =
     {
+        EnableInMemoryCrossProjectReferences: bool
         AllowStaleCompletionResults: bool
         TimeUntilStaleCompletion: int
         EnableParallelReferenceResolution: bool
@@ -92,6 +93,7 @@ type LanguageServicePerformanceOptions =
 
     static member Default =
         {
+            EnableInMemoryCrossProjectReferences = true
             AllowStaleCompletionResults = true
             TimeUntilStaleCompletion = 2000 // In ms, so this is 2 seconds
             EnableParallelReferenceResolution = false
@@ -227,6 +229,9 @@ module EditorOptionsExtensions =
         member private this.EditorOptions =
             this.Solution.Workspace.Services.GetService<EditorOptions>()
 
+        member this.AreFSharpInMemoryCrossProjectReferencesEnabled =
+            this.EditorOptions.LanguageServicePerformance.EnableInMemoryCrossProjectReferences
+
         member this.IsFSharpCodeFixesAlwaysPlaceOpensAtTopLevelEnabled =
             this.EditorOptions.CodeFixes.AlwaysPlaceOpensAtTopLevel
 

vsintegration/src/FSharp.UIResources/LanguageServicePerformanceOptionControl.xaml

@@ -19,6 +19,10 @@
             <StackPanel>
                 <GroupBox Header="{x:Static local:Strings.Project_Performance}">
                     <StackPanel>
+                        <CheckBox x:Name="enableInMemoryCrossProjectReferences"
+                                  IsChecked="{Binding EnableInMemoryCrossProjectReferences}"
+                                  Content="{x:Static local:Strings.Enable_in_memory_cross_project_references}"
+                                  ToolTip="{x:Static local:Strings.Tooltip_in_memory_cross_project_references}"/>
                         <CheckBox x:Name="enablePartialTypeChecking"
                                   IsChecked="{Binding EnablePartialTypeChecking}"
                                   Content="{x:Static local:Strings.Enable_partial_type_checking}" />

vsintegration/src/FSharp.UIResources/Strings.resx

@@ -147,6 +147,9 @@
   <data name="Show_completion_list_after_a_character_is_typed" xml:space="preserve">
     <value>_Show completion list after a character is typed</value>
   </data>
+  <data name="Enable_in_memory_cross_project_references" xml:space="preserve">
+    <value>_Enable in-memory cross project references</value>
+  </data>
   <data name="Show_navigation_links_as" xml:space="preserve">
     <value>S_how navigation links as</value>
   </data>
@@ -192,6 +195,9 @@
   <data name="Enable_Stale_IntelliSense_Results" xml:space="preserve">
     <value>Enable stale data for IntelliSense features</value>
   </data>
+  <data name="Tooltip_in_memory_cross_project_references" xml:space="preserve">
+    <value>In-memory cross-project references store project-level data in memory to allow IDE features to work across projects.</value>
+  </data>
   <data name="Enter_key_always" xml:space="preserve">
     <value>Always add new line on enter</value>
   </data>