Clearing cache of projects that are not in the current solution

src/fsharp/service/service.fs

@@ -846,6 +846,12 @@ type BackgroundCompiler(legacyReferenceResolver, projectCacheSize, keepAssemblyC
                 if startBackgroundCompileIfAlreadySeen then 
                    bc.CheckProjectInBackground(options, userOpName + ".StartBackgroundCompile"))
 
+    member bc.ClearCache(options : FSharpProjectOptions seq, userOpName) =
+        // This operation can't currently be cancelled nor awaited
+        reactor.EnqueueOp(userOpName, "ClearCache", String.Empty, fun ctok -> 
+            options
+            |> Seq.iter (fun options -> incrementalBuildersCache.RemoveAnySimilar(ctok, options)))
+
     member __.NotifyProjectCleaned (options : FSharpProjectOptions, userOpName) =
         reactor.EnqueueAndAwaitOpAsync(userOpName, "NotifyProjectCleaned", options.ProjectFileName, fun ctok -> 
          cancellable {
@@ -1142,6 +1148,11 @@ type FSharpChecker(legacyReferenceResolver,
         let userOpName = defaultArg userOpName "Unknown"
         backgroundCompiler.InvalidateConfiguration(options, startBackgroundCompile, userOpName)
 
+    /// Clear the internal cache of the given projects.
+    member __.ClearCache(options: FSharpProjectOptions seq, ?userOpName: string) =
+        let userOpName = defaultArg userOpName "Unknown"
+        backgroundCompiler.ClearCache(options, userOpName)
+
     /// This function is called when a project has been cleaned, and thus type providers should be refreshed.
     member __.NotifyProjectCleaned(options: FSharpProjectOptions, ?userOpName: string) =
         let userOpName = defaultArg userOpName "Unknown"

src/fsharp/service/service.fsi

@@ -358,6 +358,11 @@ type public FSharpChecker =
     /// <param name="userOpName">An optional string used for tracing compiler operations associated with this request.</param>
     member InvalidateConfiguration: options: FSharpProjectOptions * ?startBackgroundCompileIfAlreadySeen: bool * ?userOpName: string -> unit
 
+    /// Clear the internal cache of the given projects.
+    /// <param name="options">The given project options.</param>
+    /// <param name="userOpName">An optional string used for tracing compiler operations associated with this request.</param>
+    member ClearCache: options: FSharpProjectOptions seq * ?userOpName: string -> unit
+
     /// Set the project to be checked in the background.  Overrides any previous call to <c>CheckProjectInBackground</c>
     member CheckProjectInBackground: options: FSharpProjectOptions  * ?userOpName: string -> unit
 

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

@@ -81,7 +81,7 @@ type private FSharpProjectOptionsMessage =
     | ClearSingleFileOptionsCache of DocumentId
 
 [<Sealed>]
-type private FSharpProjectOptionsReactor (_workspace: VisualStudioWorkspace, settings: EditorOptions, _serviceProvider, checkerProvider: FSharpCheckerProvider) =
+type private FSharpProjectOptionsReactor (workspace: Workspace, settings: EditorOptions, _serviceProvider, checkerProvider: FSharpCheckerProvider) =
     let cancellationTokenSource = new CancellationTokenSource()
 
     // Hack to store command line options from HandleCommandLineChanges
@@ -208,6 +208,22 @@ type private FSharpProjectOptionsReactor (_workspace: VisualStudioWorkspace, set
                 if Array.isEmpty projectOptions.SourceFiles then
                     return None
                 else
+                    // Clear any caches that need clearing and invalidate the project.
+                    let currentSolution = workspace.CurrentSolution
+                    let projectsToClearCache =
+                        cache
+                        |> Seq.filter (fun pair -> not (currentSolution.ContainsProject pair.Key))
+
+                    if not (Seq.isEmpty projectsToClearCache) then
+                        projectsToClearCache
+                        |> Seq.iter (fun pair -> cache.Remove pair.Key |> ignore)
+                        let options =
+                            projectsToClearCache
+                            |> Seq.map (fun pair ->
+                                let _, _, projectOptions = pair.Value
+                                projectOptions)
+                        checkerProvider.Checker.ClearCache(options, userOpName = "tryComputeOptions")
+
                     checkerProvider.Checker.InvalidateConfiguration(projectOptions, startBackgroundCompileIfAlreadySeen = false, userOpName = "computeOptions")
 
                     let parsingOptions, _ = checkerProvider.Checker.GetParsingOptionsFromProjectOptions(projectOptions)