enable preview LSP support in VS

VisualFSharp.sln

@@ -158,6 +158,8 @@ Project("{6EC3EE1D-3C4E-46DD-8F32-0CC8E7565705}") = "FSharp.Compiler.LanguageSer
 EndProject
 Project("{6EC3EE1D-3C4E-46DD-8F32-0CC8E7565705}") = "FSharp.Compiler.LanguageServer.UnitTests", "tests\FSharp.Compiler.LanguageServer.UnitTests\FSharp.Compiler.LanguageServer.UnitTests.fsproj", "{AAF2D233-1C38-4090-8FFA-F7C545625E06}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FSharp.Editor.Helpers", "vsintegration\src\FSharp.Editor.Helpers\FSharp.Editor.Helpers.csproj", "{79255A92-ED00-40BA-9D64-12FCC664A976}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -912,6 +914,18 @@ Global
 		{AAF2D233-1C38-4090-8FFA-F7C545625E06}.Release|Any CPU.Build.0 = Release|Any CPU
 		{AAF2D233-1C38-4090-8FFA-F7C545625E06}.Release|x86.ActiveCfg = Release|Any CPU
 		{AAF2D233-1C38-4090-8FFA-F7C545625E06}.Release|x86.Build.0 = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Debug|x86.Build.0 = Debug|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Proto|Any CPU.ActiveCfg = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Proto|Any CPU.Build.0 = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Proto|x86.ActiveCfg = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Proto|x86.Build.0 = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Release|Any CPU.Build.0 = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Release|x86.ActiveCfg = Release|Any CPU
+		{79255A92-ED00-40BA-9D64-12FCC664A976}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -986,6 +1000,7 @@ Global
 		{8EC30B2E-F1F9-4A98-BBB5-DD0CF6C84DDC} = {647810D0-5307-448F-99A2-E83917010DAE}
 		{60BAFFA5-6631-4328-B044-2E012AB76DCA} = {B8DDA694-7939-42E3-95E5-265C2217C142}
 		{AAF2D233-1C38-4090-8FFA-F7C545625E06} = {CFE3259A-2D30-4EB0-80D5-E8B5F3D01449}
+		{79255A92-ED00-40BA-9D64-12FCC664A976} = {4C7B48D7-19AF-4AE7-9D1D-3BB289D5480D}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {48EDBBBE-C8EE-4E3C-8B19-97184A487B37}

eng/Signing.props

@@ -0,0 +1,8 @@
+<Project>
+
+  <ItemGroup>
+    <FileSignInfo Include="Nerdbank.Streams.dll" CertificateName="None" />
+    <FileSignInfo Include="Newtonsoft.Json.dll" CertificateName="None" />
+  </ItemGroup>
+
+</Project>

eng/Versions.props

@@ -92,7 +92,7 @@
     <SystemThreadingTasksParallelVersion>4.3.0</SystemThreadingTasksParallelVersion>
     <SystemThreadingThreadVersion>4.3.0</SystemThreadingThreadVersion>
     <SystemThreadingThreadPoolVersion>4.3.0</SystemThreadingThreadPoolVersion>
-    <SystemValueTupleVersion>4.4.0</SystemValueTupleVersion>
+    <SystemValueTupleVersion>4.5.0</SystemValueTupleVersion>
     <!-- Roslyn packages -->
     <MicrosoftCodeAnalysisEditorFeaturesVersion>$(RoslynVersion)</MicrosoftCodeAnalysisEditorFeaturesVersion>
     <MicrosoftCodeAnalysisEditorFeaturesTextVersion>$(RoslynVersion)</MicrosoftCodeAnalysisEditorFeaturesTextVersion>
@@ -115,6 +115,7 @@
     <MicrosoftVisualStudioEditorVersion>16.0.467</MicrosoftVisualStudioEditorVersion>
     <MicrosoftVisualStudioImageCatalogVersion>16.0.28727</MicrosoftVisualStudioImageCatalogVersion>
     <MicrosoftVisualStudioImagingVersion>16.0.28729</MicrosoftVisualStudioImagingVersion>
+    <MicrosoftVisualStudioLanguageServerClientVersion>16.1.3121</MicrosoftVisualStudioLanguageServerClientVersion>
     <MicrosoftVisualStudioLanguageStandardClassificationVersion>16.0.467</MicrosoftVisualStudioLanguageStandardClassificationVersion>
     <MicrosoftVisualStudioLanguageVersion>16.0.467</MicrosoftVisualStudioLanguageVersion>
     <MicrosoftVisualStudioLanguageIntellisenseVersion>16.0.467</MicrosoftVisualStudioLanguageIntellisenseVersion>

eng/targets/Settings.props

@@ -7,4 +7,8 @@
     <NuspecBasePath>$(ArtifactsBinDir)</NuspecBasePath>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <IncludeVsLanguageServer>true</IncludeVsLanguageServer>
+  </PropertyGroup>
+
 </Project>

src/fsharp/FSharp.Compiler.LanguageServer/FSharp.Compiler.LanguageServer.fsproj

@@ -11,8 +11,11 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="State.fs" />
+    <Compile Include="JsonDUConverter.fs" />
+    <Compile Include="JsonOptionConverter.fs" />
     <Compile Include="LspTypes.fs" />
+    <Compile Include="LspExternalAccess.fs" />
+    <Compile Include="State.fs" />
     <Compile Include="TextDocument.fs" />
     <Compile Include="Methods.fs" />
     <Compile Include="Server.fs" />
@@ -28,4 +31,19 @@
     <PackageReference Include="StreamJsonRpc" Version="$(StreamJsonRpcVersion)" />
   </ItemGroup>
 
+  <Target Name="GatherPublishedProjectOutputGroupItems"
+          DependsOnTargets="Publish">
+    <ItemGroup>
+      <_PublishedProjectOutputGroupFiles Include="$(PublishDir)\**" />
+    </ItemGroup>
+  </Target>
+
+  <Target Name="PublishedProjectOutputGroup"
+          Returns="@(PublishedProjectOutputGroupOutput)"
+          DependsOnTargets="GatherPublishedProjectOutputGroupItems">
+    <ItemGroup>
+      <PublishedProjectOutputGroupOutput Include="@(_PublishedProjectOutputGroupFiles)" TargetPath="Agent\%(RecursiveDir)%(FileName)%(Extension)" />
+    </ItemGroup>
+  </Target>
+
 </Project>

src/fsharp/FSharp.Compiler.LanguageServer/JsonDUConverter.fs

@@ -0,0 +1,18 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.LanguageServer
+
+open System
+open FSharp.Reflection
+open Newtonsoft.Json
+
+type JsonDUConverter() =
+    inherit JsonConverter()
+    override __.CanConvert(typ) = FSharpType.IsUnion(typ)
+    override __.WriteJson(writer, value, _serializer) =
+        writer.WriteValue(value.ToString().ToLowerInvariant())
+    override __.ReadJson(reader, typ, x, serializer) =
+        let cases = FSharpType.GetUnionCases(typ)
+        let str = serializer.Deserialize(reader, typeof<string>) :?> string
+        let case = cases |> Array.find (fun c -> String.Compare(c.Name, str, StringComparison.OrdinalIgnoreCase) = 0)
+        FSharpValue.MakeUnion(case, [||])

src/fsharp/FSharp.Compiler.LanguageServer/JsonOptionConverter.fs

@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.LanguageServer
+
+open System
+open FSharp.Reflection
+open Newtonsoft.Json
+
+type JsonOptionConverter() =
+    inherit JsonConverter()
+    override __.CanConvert(typ) = typ.IsGenericType && typ.GetGenericTypeDefinition() = typedefof<option<_>>
+    override __.WriteJson(writer, value, serializer) =
+        let value = match value with
+                    | null -> null
+                    | _ ->
+                        let _, fields =  FSharpValue.GetUnionFields(value, value.GetType())
+                        fields.[0]
+        serializer.Serialize(writer, value)
+    override __.ReadJson(reader, typ, _, serializer) =
+        let innerType = typ.GetGenericArguments().[0]
+        let innerType =
+            if innerType.IsValueType then (typedefof<Nullable<_>>).MakeGenericType([|innerType|])
+            else innerType
+        let value = serializer.Deserialize(reader, innerType)
+        let cases = FSharpType.GetUnionCases(typ)
+        if value = null then FSharpValue.MakeUnion(cases.[0], [||])
+        else FSharpValue.MakeUnion(cases.[1], [|value|])

src/fsharp/FSharp.Compiler.LanguageServer/LspExternalAccess.fs

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.LanguageServer
+
+open StreamJsonRpc
+
+[<AutoOpen>]
+module FunctionNames =
+    [<Literal>]
+    let OptionsSet = "options/set"
+
+type Options =
+    { usePreviewTextHover: bool }
+    static member Default() =
+        { usePreviewTextHover = false }
+
+module Extensions =
+    type JsonRpc with
+        member jsonRpc.SetOptionsAsync (options: Options) =
+            async {
+                do! jsonRpc.InvokeAsync(OptionsSet, options) |> Async.AwaitTask
+            }

src/fsharp/FSharp.Compiler.LanguageServer/LspTypes.fs

@@ -2,8 +2,11 @@
 
 namespace FSharp.Compiler.LanguageServer
 
-// Interfaces as defined at https://microsoft.github.io/language-server-protocol/specification.  The properties on these
-// types are camlCased to match the underlying JSON properties to avoid attributes on every field:
+open Newtonsoft.Json.Linq
+open Newtonsoft.Json
+
+// Interfaces as defined at https://microsoft.github.io/language-server-protocol/specification.  The properties on
+// these types are camlCased to match the underlying JSON properties to avoid attributes on every field:
 //   [<JsonProperty("camlCased")>]
 
 /// Represents a zero-based line and column of a text document.
@@ -27,11 +30,11 @@ type DiagnosticRelatedInformation =
 
 type Diagnostic =
     { range: Range
-      severity: int
+      severity: int option
       code: string
-      source: string // "F#"
+      source: string option // "F#"
       message: string
-      relatedInformation: DiagnosticRelatedInformation[] }
+      relatedInformation: DiagnosticRelatedInformation[] option }
     static member Error = 1
     static member Warning = 2
     static member Information = 3
@@ -41,9 +44,23 @@ type PublishDiagnosticsParams =
     { uri: DocumentUri
       diagnostics: Diagnostic[] }
 
-type InitializeParams = string // TODO:
+type ClientCapabilities =
+    { workspace: JToken option // TODO: WorkspaceClientCapabilities
+      textDocument: JToken option // TODO: TextDocumentCapabilities
+      experimental: JToken option
+      supportsVisualStudioExtensions: bool option }
+
+[<JsonConverter(typeof<JsonDUConverter>)>]
+type Trace =
+    | Off
+    | Messages
+    | Verbose
 
-// Note, this type has many more optional values that can be expanded as support is added.
+type WorkspaceFolder =
+    { uri: DocumentUri
+      name: string }
+
+/// Note, this type has many more optional values that can be expanded as support is added.
 type ServerCapabilities =
     { hoverProvider: bool }
     static member DefaultCapabilities() =
@@ -52,6 +69,7 @@ type ServerCapabilities =
 type InitializeResult =
     { capabilities: ServerCapabilities }
 
+[<JsonConverter(typeof<JsonDUConverter>)>]
 type MarkupKind =
     | PlainText
     | Markdown
@@ -66,7 +84,3 @@ type Hover =
 
 type TextDocumentIdentifier =
     { uri: DocumentUri }
-
-type TextDocumentPositionParams =
-    { textDocument: TextDocumentIdentifier
-      position: Position }

src/fsharp/FSharp.Compiler.LanguageServer/Methods.fs

@@ -2,21 +2,66 @@
 
 namespace FSharp.Compiler.LanguageServer
 
+open System
+open System.Runtime.InteropServices
+open System.Threading
+open Newtonsoft.Json.Linq
 open StreamJsonRpc
 
 // https://microsoft.github.io/language-server-protocol/specification
 type Methods(state: State) =
 
+    /// Helper to run Async<'T> with a CancellationToken.
+    let runAsync (cancellationToken: CancellationToken) (computation: Async<'T>) = Async.StartAsTask(computation, cancellationToken=cancellationToken)
+
+    member __.State = state
+
+    //--------------------------------------------------------------------------
+    // official LSP methods
+    //--------------------------------------------------------------------------
+
     [<JsonRpcMethod("initialize")>]
-    member __.Initialize (args: InitializeParams) =
-        async {
-            // note, it's important that this method is `async` because unit tests can then properly verify that the
-            // JSON RPC handling of async methods is correct
-            return ServerCapabilities.DefaultCapabilities()
-        } |> Async.StartAsTask
+    member __.Initialize
+        (
+            processId: Nullable<int>,
+            [<Optional; DefaultParameterValue(null: string)>] rootPath: string,
+            [<Optional; DefaultParameterValue(null: string)>] rootUri: DocumentUri,
+            [<Optional; DefaultParameterValue(null: JToken)>] initializationOptions: JToken,
+            capabilities: ClientCapabilities,
+            [<Optional; DefaultParameterValue(null: string)>] trace: string,
+            [<Optional; DefaultParameterValue(null: WorkspaceFolder[])>] workspaceFolders: WorkspaceFolder[]
+        ) =
+        { InitializeResult.capabilities = ServerCapabilities.DefaultCapabilities() }
+
+    [<JsonRpcMethod("initialized")>]
+    member __.Initialized () = ()
 
     [<JsonRpcMethod("shutdown")>]
-    member __.Shutdown() = state.DoShutdown()
+    member __.Shutdown(): obj = state.DoShutdown(); null
+
+    [<JsonRpcMethod("exit")>]
+    member __.Exit() = state.DoExit()
+
+    [<JsonRpcMethod("$/cancelRequest")>]
+    member __.cancelRequest (id: JToken) = state.DoCancel()
 
     [<JsonRpcMethod("textDocument/hover")>]
-    member __.TextDocumentHover (args: TextDocumentPositionParams) = TextDocument.Hover(state, args) |> Async.StartAsTask
+    member __.TextDocumentHover
+        (
+            textDocument: TextDocumentIdentifier,
+            position: Position,
+            [<Optional; DefaultParameterValue(CancellationToken())>] cancellationToken: CancellationToken
+        ) =
+        TextDocument.Hover state textDocument position |> runAsync cancellationToken
+
+    //--------------------------------------------------------------------------
+    // unofficial LSP methods that we implement separately
+    //--------------------------------------------------------------------------
+
+    [<JsonRpcMethod(OptionsSet)>]
+    member __.OptionsSet
+        (
+            options: Options
+        ) =
+        sprintf "got options %A" options |> Console.Error.WriteLine
+        state.Options <- options

src/fsharp/FSharp.Compiler.LanguageServer/Server.fs

@@ -8,16 +8,21 @@ open StreamJsonRpc
 
 type Server(sendingStream: Stream, receivingStream: Stream) =
 
+    let formatter = JsonMessageFormatter()
+    let converter = JsonOptionConverter() // special handler to convert between `Option<'T>` and `obj/null`.
+    do formatter.JsonSerializer.Converters.Add(converter)
+    let handler = new HeaderDelimitedMessageHandler(sendingStream, receivingStream, formatter)
     let state = State()
     let methods = Methods(state)
-    let rpc = new JsonRpc(sendingStream, receivingStream, methods)
+    let rpc = new JsonRpc(handler, methods)
 
     member __.StartListening() =
         rpc.StartListening()
 
     member __.WaitForExitAsync() =
         async {
             do! Async.AwaitEvent (state.Shutdown)
+            do! Async.AwaitEvent (state.Exit)
         }
 
     interface IDisposable with

src/fsharp/FSharp.Compiler.LanguageServer/State.fs

@@ -5,8 +5,22 @@ namespace FSharp.Compiler.LanguageServer
 type State() =
 
     let shutdownEvent = new Event<_>()
+    let exitEvent = new Event<_>()
+    let cancelEvent = new Event<_>()
 
     [<CLIEvent>]
     member __.Shutdown = shutdownEvent.Publish
 
+    [<CLIEvent>]
+    member __.Exit = exitEvent.Publish
+
+    [<CLIEvent>]
+    member __.Cancel = cancelEvent.Publish
+
     member __.DoShutdown() = shutdownEvent.Trigger()
+
+    member __.DoExit() = exitEvent.Trigger()
+
+    member __.DoCancel() = cancelEvent.Trigger()
+
+    member val Options = Options.Default() with get, set