Cache parsing results in incremental build

docs/builder-caches.md

@@ -0,0 +1,13 @@
+---
+title: IncrementalBuilder caches
+category: Language Service Internals
+categoryindex: 300
+index: 1300
+---
+# IncrementalBuilder SyntaxTree cache
+
+Incremental builder keeps in a cache at most one `ParsedInput` for each file it parses.
+This behavior can be toggled with `useSyntaxTreeCache` parameter.
+
+Memory impact of this feature can be in range of tens of MB for larger solutions. This can be inspected in memory profilng tools by searching for `ParsedInput` instances.
+When partial checking is enabled, implementation files backed by signature will not be parsed or cached, as expected.

src/Compiler/Service/IncrementalBuild.fsi

@@ -269,7 +269,8 @@ type internal IncrementalBuilder =
         parallelReferenceResolution: ParallelReferenceResolution *
         captureIdentifiersWhenParsing: bool *
         getSource: (string -> ISourceText option) option *
-        useChangeNotifications: bool ->
+        useChangeNotifications: bool *
+        useSyntaxTreeCache: bool ->
             NodeCode<IncrementalBuilder option * FSharpDiagnostic[]>
 
 /// Generalized Incremental Builder. This is exposed only for unit testing purposes.

src/Compiler/Service/service.fs

@@ -195,7 +195,8 @@ type BackgroundCompiler
         parallelReferenceResolution,
         captureIdentifiersWhenParsing,
         getSource: (string -> ISourceText option) option,
-        useChangeNotifications
+        useChangeNotifications,
+        useSyntaxTreeCache
     ) as self =
 
     let beforeFileChecked = Event<string * FSharpProjectOptions>()
@@ -329,7 +330,8 @@ type BackgroundCompiler
                     parallelReferenceResolution,
                     captureIdentifiersWhenParsing,
                     getSource,
-                    useChangeNotifications
+                    useChangeNotifications,
+                    useSyntaxTreeCache
                 )
 
             match builderOpt with
@@ -636,9 +638,6 @@ type BackgroundCompiler
         ) =
 
         node {
-            if useChangeNotifications then
-                do! builder.NotifyFileChanged(fileName, DateTime.UtcNow)
-
             match! bc.GetCachedCheckFileResult(builder, fileName, sourceText, options) with
             | Some (_, results) -> return FSharpCheckFileAnswer.Succeeded results
             | _ ->
@@ -1263,7 +1262,8 @@ type FSharpChecker
         parallelReferenceResolution,
         captureIdentifiersWhenParsing,
         getSource,
-        useChangeNotifications
+        useChangeNotifications,
+        useSyntaxTreeCache
     ) =
 
     let backgroundCompiler =
@@ -1280,7 +1280,8 @@ type FSharpChecker
             parallelReferenceResolution,
             captureIdentifiersWhenParsing,
             getSource,
-            useChangeNotifications
+            useChangeNotifications,
+            useSyntaxTreeCache
         )
 
     static let globalInstance = lazy FSharpChecker.Create()
@@ -1324,7 +1325,8 @@ type FSharpChecker
             ?enablePartialTypeChecking,
             ?parallelReferenceResolution: bool,
             ?captureIdentifiersWhenParsing: bool,
-            ?documentSource: DocumentSource
+            ?documentSource: DocumentSource,
+            ?useSyntaxTreeCache: bool
         ) =
 
         use _ = Activity.startNoTags "FSharpChecker.Create"
@@ -1352,6 +1354,8 @@ type FSharpChecker
             | Some (DocumentSource.Custom _) -> true
             | _ -> false
 
+        let useSyntaxTreeCache = defaultArg useSyntaxTreeCache true
+
         if keepAssemblyContents && enablePartialTypeChecking then
             invalidArg "enablePartialTypeChecking" "'keepAssemblyContents' and 'enablePartialTypeChecking' cannot be both enabled."
 
@@ -1372,7 +1376,8 @@ type FSharpChecker
             (match documentSource with
              | Some (DocumentSource.Custom f) -> Some f
              | _ -> None),
-            useChangeNotifications
+            useChangeNotifications,
+            useSyntaxTreeCache
         )
 
     member _.ReferenceResolver = legacyReferenceResolver

src/Compiler/Service/service.fsi

@@ -41,6 +41,7 @@ type public FSharpChecker =
     /// <param name="parallelReferenceResolution">Indicates whether to resolve references in parallel.</param>
     /// <param name="captureIdentifiersWhenParsing">When set to true we create a set of all identifiers for each parsed file which can be used to speed up finding references.</param>
     /// <param name="documentSource">Default: FileSystem. You can use Custom source to provide a function that will return the source for a given file path instead of reading it from the file system. Note that with this option the FSharpChecker will also not monitor the file system for file changes. It will expect to be notified of changes via the NotifyFileChanged method.</param>
+    /// <param name="useSyntaxTreeCache">Default: true. Indicates whether to keep parsing results in a cache.</param>
     static member Create:
         ?projectCacheSize: int *
         ?keepAssemblyContents: bool *
@@ -53,7 +54,8 @@ type public FSharpChecker =
         ?enablePartialTypeChecking: bool *
         ?parallelReferenceResolution: bool *
         ?captureIdentifiersWhenParsing: bool *
-        [<Experimental "This parameter is experimental and likely to be removed in the future.">] ?documentSource: DocumentSource ->
+        [<Experimental "This parameter is experimental and likely to be removed in the future.">] ?documentSource: DocumentSource *
+        [<Experimental "This parameter is experimental and likely to be removed in the future.">] ?useSyntaxTreeCache: bool ->
             FSharpChecker
 
     /// <summary>
@@ -383,7 +385,6 @@ type public FSharpChecker =
     member ClearLanguageServiceRootCachesAndCollectAndFinalizeAllTransients: unit -> unit
 
     /// Notify the checker that given file has changed. This needs to be used when checker is created with documentSource = Custom.
-    /// Although it is not mandatory when the changed file is the next thing requested to be checked.
     [<Experimental "This FCS API is experimental and likely to be removed in the future.">]
     member NotifyFileChanged: fileName: string * options: FSharpProjectOptions * ?userOpName: string -> Async<unit>
 

src/Compiler/Utilities/Activity.fs

@@ -10,6 +10,8 @@ open System.Text
 [<RequireQualifiedAccess>]
 module internal Activity =
 
+    let FscSourceName = "fsc"
+
     module Tags =
         let fileName = "fileName"
         let project = "project"
@@ -40,7 +42,10 @@ module internal Activity =
                 outputDllFile
             |]
 
-    let private activitySourceName = "fsc"
+    module Events =
+        let cacheHit = "cacheHit"
+
+    let private activitySourceName = FscSourceName
     let private profiledSourceName = "fsc_with_env_stats"
 
     type System.Diagnostics.Activity with
@@ -75,6 +80,10 @@ module internal Activity =
 
     let startNoTags (name: string) : IDisposable = activitySource.StartActivity(name)
 
+    let addEvent name =
+        if Activity.Current <> null && Activity.Current.Source = activitySource then
+            Activity.Current.AddEvent(ActivityEvent(name)) |> ignore
+
     module Profiling =
 
         module Tags =

src/Compiler/Utilities/Activity.fsi

@@ -9,6 +9,8 @@ open System
 [<RequireQualifiedAccess>]
 module internal Activity =
 
+    val FscSourceName: string
+
     module Tags =
         val fileName: string
         val qualifiedNameOfFile: string
@@ -17,10 +19,15 @@ module internal Activity =
         val length: string
         val cache: string
 
+    module Events =
+        val cacheHit: string
+
     val startNoTags: name: string -> IDisposable
 
     val start: name: string -> tags: (string * string) seq -> IDisposable
 
+    val addEvent: name: string -> unit
+
     module Profiling =
         val startAndMeasureEnvironmentStats: name: string -> IDisposable
         val addConsoleListener: unit -> IDisposable

tests/FSharp.Compiler.ComponentTests/FSharpChecker/CommonWorkflows.fs

@@ -2,6 +2,7 @@
 
 open System
 open System.IO
+open System.Diagnostics
 
 open Xunit
 
@@ -10,6 +11,22 @@ open FSharp.Test.ProjectGeneration.Internal
 open FSharp.Compiler.Text
 open FSharp.Compiler.CodeAnalysis
 
+module FcsDiagnostics = FSharp.Compiler.Diagnostics.Activity
+
+let expectCacheHits n =
+    let events = ResizeArray()
+    let listener = 
+        new ActivityListener(
+            ShouldListenTo = (fun s -> s.Name = FcsDiagnostics.FscSourceName),
+            Sample = (fun _ -> ActivitySamplingResult.AllData),
+            ActivityStopped = (fun a -> events.AddRange a.Events)
+        )
+    ActivitySource.AddActivityListener listener
+    { new IDisposable with 
+        member this.Dispose() =
+            listener.Dispose()
+            Assert.Equal(n, events |> Seq.filter (fun e -> e.Name = FcsDiagnostics.Events.cacheHit) |> Seq.length) }
+
 let makeTestProject () =
     SyntheticProject.Create(
         sourceFile "First" [],
@@ -132,3 +149,62 @@ let ``Using getSource and notifications instead of filesystem`` () =
         checkFile middle expectSignatureChanged
         checkFile last expectSignatureChanged
     }
+
+[<Fact>]
+let ``Using getSource and notifications instead of filesystem with parse caching`` () =
+
+    let size = 20
+
+    let project =
+        { SyntheticProject.Create() with
+            SourceFiles = [
+                sourceFile $"File%03d{0}" []
+                for i in 1..size do
+                    sourceFile $"File%03d{i}" [$"File%03d{i-1}"]
+            ]
+        }
+
+    let first = "File001"
+    let middle = $"File%03d{size / 2}"
+    let last = $"File%03d{size}"
+
+    use _ = expectCacheHits 28
+    ProjectWorkflowBuilder(project, useGetSource = true, useChangeNotifications = true, useSyntaxTreeCache = true) {
+        updateFile first updatePublicSurface
+        checkFile first expectSignatureChanged
+        checkFile last expectSignatureChanged
+        updateFile middle updatePublicSurface
+        checkFile last expectSignatureChanged
+        addFileAbove middle (sourceFile "addedFile" [first])
+        updateFile middle (addDependency "addedFile")
+        checkFile middle expectSignatureChanged
+        checkFile last expectSignatureChanged
+    }
+
+[<Fact>]
+let ``Edit file, check it, then check dependent file with parse caching`` () =
+    use _ = expectCacheHits 1
+    ProjectWorkflowBuilder(makeTestProject(), useSyntaxTreeCache = true) {
+        updateFile "First" breakDependentFiles
+        checkFile "First" expectSignatureChanged
+        saveFile "First"
+        checkFile "Second" expectErrors
+    }
+
+[<Fact>]
+let ``Edit file, don't check it, check dependent file with parse caching `` () =
+    use _ = expectCacheHits 1
+    ProjectWorkflowBuilder(makeTestProject(), useSyntaxTreeCache = true) {
+        updateFile "First" breakDependentFiles
+        saveFile "First"
+        checkFile "Second" expectErrors
+    }
+
+[<Fact>]
+let ``Parse cache not used when not enabled`` () =
+    use _ = expectCacheHits 0
+    ProjectWorkflowBuilder(makeTestProject(), useSyntaxTreeCache = false) {
+        updateFile "First" breakDependentFiles
+        saveFile "First"
+        checkFile "Second" expectErrors
+    }

tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.SurfaceArea.netstandard20.debug.bsl

@@ -2031,7 +2031,7 @@ FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: FSharp.Compiler.Symbols.
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String ToString()
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String[] DependencyFiles
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String[] get_DependencyFiles()
-FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Create(Microsoft.FSharp.Core.FSharpOption`1[System.Int32], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.LegacyReferenceResolver], Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpFunc`2[System.Tuple`2[System.String,System.DateTime],Microsoft.FSharp.Core.FSharpOption`1[System.Tuple`3[System.Object,System.IntPtr,System.Int32]]]], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.DocumentSource])
+FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Create(Microsoft.FSharp.Core.FSharpOption`1[System.Int32], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.LegacyReferenceResolver], Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpFunc`2[System.Tuple`2[System.String,System.DateTime],Microsoft.FSharp.Core.FSharpOption`1[System.Tuple`3[System.Object,System.IntPtr,System.Int32]]]], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.DocumentSource], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean])
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Instance
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker get_Instance()
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpProjectOptions GetProjectOptionsFromCommandLineArgs(System.String, System.String[], Microsoft.FSharp.Core.FSharpOption`1[System.DateTime], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean])

tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.SurfaceArea.netstandard20.release.bsl

@@ -2031,7 +2031,7 @@ FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: FSharp.Compiler.Symbols.
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String ToString()
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String[] DependencyFiles
 FSharp.Compiler.CodeAnalysis.FSharpCheckProjectResults: System.String[] get_DependencyFiles()
-FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Create(Microsoft.FSharp.Core.FSharpOption`1[System.Int32], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.LegacyReferenceResolver], Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpFunc`2[System.Tuple`2[System.String,System.DateTime],Microsoft.FSharp.Core.FSharpOption`1[System.Tuple`3[System.Object,System.IntPtr,System.Int32]]]], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.DocumentSource])
+FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Create(Microsoft.FSharp.Core.FSharpOption`1[System.Int32], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.LegacyReferenceResolver], Microsoft.FSharp.Core.FSharpOption`1[Microsoft.FSharp.Core.FSharpFunc`2[System.Tuple`2[System.String,System.DateTime],Microsoft.FSharp.Core.FSharpOption`1[System.Tuple`3[System.Object,System.IntPtr,System.Int32]]]], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[FSharp.Compiler.CodeAnalysis.DocumentSource], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean])
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker Instance
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpChecker get_Instance()
 FSharp.Compiler.CodeAnalysis.FSharpChecker: FSharp.Compiler.CodeAnalysis.FSharpProjectOptions GetProjectOptionsFromCommandLineArgs(System.String, System.String[], Microsoft.FSharp.Core.FSharpOption`1[System.DateTime], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean], Microsoft.FSharp.Core.FSharpOption`1[System.Boolean])

tests/FSharp.Test.Utilities/ProjectGeneration.fs

@@ -502,7 +502,8 @@ type ProjectWorkflowBuilder
         ?initialContext,
         ?checker: FSharpChecker,
         ?useGetSource,
-        ?useChangeNotifications
+        ?useChangeNotifications,
+        ?useSyntaxTreeCache
     ) =
 
     let useGetSource = defaultArg useGetSource false
@@ -533,7 +534,8 @@ type ProjectWorkflowBuilder
                 enableBackgroundItemKeyStoreAndSemanticClassification = true,
                 enablePartialTypeChecking = true,
                 captureIdentifiersWhenParsing = true,
-                documentSource = (if useGetSource then DocumentSource.Custom getSource else DocumentSource.FileSystem)
+                documentSource = (if useGetSource then DocumentSource.Custom getSource else DocumentSource.FileSystem),
+                useSyntaxTreeCache = defaultArg useSyntaxTreeCache false
             ))
 
     let mapProjectAsync f workflow =

vsintegration/src/FSharp.Editor/FSharp.Editor.resx

@@ -207,7 +207,7 @@ Time until stale results are used (in milliseconds);
 Parallelization (requires restart);
 Enable parallel type checking with signature files;
 Enable parallel reference resolution;
-Enable fast find references &amp; rename (experimental)</value>
+Enable fast find references &amp; rename (experimental);Cache parsing results (experimental)</value>
   </data>
   <data name="6012" xml:space="preserve">
     <value>Advanced</value>

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

@@ -122,6 +122,9 @@ type internal FSharpWorkspaceServiceFactory
                             let enableLiveBuffers =
                                 getOption (fun options -> options.Advanced.IsLiveBuffersEnabled) false
 
+                            let useSyntaxTreeCache =
+                                getOption (fun options -> options.LanguageServicePerformance.UseSyntaxTreeCache) LanguageServicePerformanceOptions.Default.UseSyntaxTreeCache
+
                             let checker =
                                 FSharpChecker.Create(
                                     projectCacheSize = 5000, // We do not care how big the cache is. VS will actually tell FCS to clear caches, so this is fine.
@@ -133,7 +136,8 @@ type internal FSharpWorkspaceServiceFactory
                                     enablePartialTypeChecking = true,
                                     parallelReferenceResolution = enableParallelReferenceResolution,
                                     captureIdentifiersWhenParsing = true,
-                                    documentSource = (if enableLiveBuffers then DocumentSource.Custom getSource else DocumentSource.FileSystem))
+                                    documentSource = (if enableLiveBuffers then DocumentSource.Custom getSource else DocumentSource.FileSystem),
+                                    useSyntaxTreeCache = useSyntaxTreeCache)
 
                             if enableLiveBuffers then
                                 workspace.WorkspaceChanged.Add(fun args ->