feat: langserver rewrite in C#

.github/workflows/ci-pr.yml

@@ -4,6 +4,11 @@ on:
   pull_request:
     branches:
       - main
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - ready_for_review
 
 permissions:
   contents: read

.github/workflows/on-push-tag.yml

@@ -45,7 +45,7 @@ jobs:
         shell: bash
         run: |
           rm -rf vscode-fscript/server
-          dotnet publish src/FScript.LanguageServer/FScript.LanguageServer.fsproj -c Release -p:PublishAot=false -o vscode-fscript/server
+          dotnet publish src/FScript.LanguageServer/FScript.LanguageServer.csproj -c Release -p:PublishAot=false -o vscode-fscript/server
 
       - name: Install extension packaging tool
         run: npm install -g @vscode/vsce@3.5

CHANGELOG.md

@@ -4,7 +4,19 @@ All notable changes to FScript are documented in this file.
 
 ## [Unreleased]
 
+- Removed F# sources from `src/FScript.LanguageServer*` by moving LSP semantic modules into `FScript.CSharpInterop` and keeping `FScript.LanguageServer` as C# host.
+- Replaced `FScript.LanguageServer.Tests` project with a C# test project and C# LSP test harness to remove F# compile cost from LanguageServer test builds.
+- Deleted obsolete F# LanguageServer test sources after C# test project migration.
+- Renamed `FScript.CSharpInterop/LanguageServerLegacy` to `FScript.CSharpInterop/LanguageServer` to reflect the new primary architecture.
+- CI now runs branch update builds on PR `synchronize` events while keeping `ci-main` scoped to `main` pushes to avoid duplicate runs.
 - Enabled F# preview parallel compilation globally, disabled deterministic builds, and removed global RuntimeIdentifiers to reduce CI build latency.
+- Added `FScript.CSharpInterop` as a stable bridge for parse/infer/runtime-extern/stdlib-source services and wired LanguageServer through it.
+- Added `FScript.LanguageServer` host executable as the migration entrypoint for C#-owned LSP startup.
+- Added a first native C# LSP server core (JSON-RPC transport, initialize/shutdown, text sync, and stdlib-source request) with dedicated integration tests.
+- Extended the native C# LSP core with diagnostics publishing and `viewAst`/`viewInferredAst` command handling.
+- Switched C# LSP host to full-method dispatch parity via shared handlers, made it the default test target, and updated extension/tag packaging to use `FScript.LanguageServer.dll`.
+- Replaced the F# LSP server executable with `FScript.LanguageServer` (C#) and moved F# LSP logic into `FScript.LanguageServer.Core`.
+- Fixed imported qualified type annotations (for example `common.ProjectInfo`) in parser/type inference to prevent false type mismatches.
 
 ## [0.33.0]
 

FScript.sln

@@ -17,9 +17,11 @@ Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "FScript.Runtime", "src\FScr
 EndProject
 Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "FScript.Runtime.Tests", "tests\FScript.Runtime.Tests\FScript.Runtime.Tests.fsproj", "{1E2C7B34-04B8-42C9-880D-CC47DEC156A7}"
 EndProject
-Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "FScript.LanguageServer", "src\FScript.LanguageServer\FScript.LanguageServer.fsproj", "{E22A34B5-F5E8-422D-9BA5-932B3C45188F}"
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FScript.LanguageServer.Tests", "tests\FScript.LanguageServer.Tests\FScript.LanguageServer.Tests.csproj", "{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}"
 EndProject
-Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "FScript.LanguageServer.Tests", "tests\FScript.LanguageServer.Tests\FScript.LanguageServer.Tests.fsproj", "{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}"
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "FScript.CSharpInterop", "src\FScript.CSharpInterop\FScript.CSharpInterop.fsproj", "{8A28B784-F90B-469C-91BE-F96F63ACEA32}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FScript.LanguageServer", "src\FScript.LanguageServer\FScript.LanguageServer.csproj", "{57518676-01F0-4D5B-A53B-7A06DBA9AA04}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -91,18 +93,6 @@ Global
 		{1E2C7B34-04B8-42C9-880D-CC47DEC156A7}.Release|x64.Build.0 = Release|Any CPU
 		{1E2C7B34-04B8-42C9-880D-CC47DEC156A7}.Release|x86.ActiveCfg = Release|Any CPU
 		{1E2C7B34-04B8-42C9-880D-CC47DEC156A7}.Release|x86.Build.0 = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|x64.ActiveCfg = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|x64.Build.0 = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|x86.ActiveCfg = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Debug|x86.Build.0 = Debug|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|Any CPU.Build.0 = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|x64.ActiveCfg = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|x64.Build.0 = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|x86.ActiveCfg = Release|Any CPU
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F}.Release|x86.Build.0 = Release|Any CPU
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Debug|x64.ActiveCfg = Debug|Any CPU
@@ -115,6 +105,30 @@ Global
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Release|x64.Build.0 = Release|Any CPU
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Release|x86.ActiveCfg = Release|Any CPU
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1}.Release|x86.Build.0 = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|x64.Build.0 = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Debug|x86.Build.0 = Debug|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|Any CPU.Build.0 = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|x64.ActiveCfg = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|x64.Build.0 = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|x86.ActiveCfg = Release|Any CPU
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32}.Release|x86.Build.0 = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|x64.Build.0 = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Debug|x86.Build.0 = Debug|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|Any CPU.Build.0 = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|x64.ActiveCfg = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|x64.Build.0 = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|x86.ActiveCfg = Release|Any CPU
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -125,7 +139,8 @@ Global
 		{9C62883E-EFB0-4D9E-84F3-4138C123F55E} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
 		{8C2C5767-857A-44B0-80C2-DC90E0A60F4D} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
 		{1E2C7B34-04B8-42C9-880D-CC47DEC156A7} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
-		{E22A34B5-F5E8-422D-9BA5-932B3C45188F} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
 		{B734E1E1-59C2-47E0-8D19-A9C5C95938F1} = {0AB3BF05-4346-4AA6-1389-037BE0695223}
+		{8A28B784-F90B-469C-91BE-F96F63ACEA32} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
+		{57518676-01F0-4D5B-A53B-7A06DBA9AA04} = {827E0CD3-B72D-47B6-A68D-7590B98EB39B}
 	EndGlobalSection
 EndGlobal

docs/architecture/assemblies-and-roles.md

@@ -55,6 +55,32 @@ Use this when:
 NuGet:
 - `MagnusOpera.FScript.Runtime`
 
+### `FScript.CSharpInterop`
+Role:
+- C#-friendly integration facade over language + runtime services.
+
+Responsibilities:
+- Resolve runtime extern catalog from source path/root context.
+- Parse with include/import expansion through a stable interop entry point.
+- Run inference APIs through a single host-facing surface.
+- Expose stdlib virtual source loading for editor integrations.
+
+Use this when:
+- You integrate FScript from C# and want to avoid direct F# compiler/runtime internals.
+- You build tooling services (for example LSP hosts) with a stable boundary.
+
+### `FScript.LanguageServer`
+Role:
+- C# host executable for the Language Server process.
+
+Responsibilities:
+- Provide the production C# process host for LSP startup/dispatch.
+- Execute the full LSP method surface used by the VS Code extension.
+- Keep protocol behavior aligned with existing language/runtime analysis services.
+
+Use this when:
+- You want C# ownership of the server host process while reusing existing language services.
+
 ## Typical composition
 
 ### CLI execution path
@@ -72,6 +98,8 @@ NuGet:
 ## Dependency direction
 - `FScript.Language` has no dependency on `FScript.Runtime`.
 - `FScript.Runtime` depends on `FScript.Language` types.
+- `FScript.CSharpInterop` depends on both `FScript.Language` and `FScript.Runtime`.
+- `FScript.LanguageServer` depends on `FScript.CSharpInterop`.
 - `FScript` depends on both `FScript.Language` and `FScript.Runtime`.
 
 This keeps the language engine reusable while runtime capabilities remain host-configurable.

src/FScript.CSharpInterop/FScript.CSharpInterop.fsproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="InteropServices.fs" />
+    <Compile Include="LanguageServer\LspProtocol.fs" />
+    <Compile Include="LanguageServer\LspModel.fs" />
+    <Compile Include="LanguageServer\LspRuntimeExterns.fs" />
+    <Compile Include="LanguageServer\AstJson.fs" />
+    <Compile Include="LanguageServer\LspSymbols.fs" />
+    <Compile Include="LanguageServer\LspHandlers.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\FScript.Language\FScript.Language.fsproj" />
+    <ProjectReference Include="..\FScript.Runtime\FScript.Runtime.fsproj" />
+  </ItemGroup>
+
+</Project>

src/FScript.CSharpInterop/InteropServices.fs

@@ -0,0 +1,63 @@
+namespace FScript.CSharpInterop
+
+open System
+open System.IO
+open FScript.Language
+open FScript.Runtime
+
+module InteropServices =
+    let private resolveRootDirectory (sourcePath: string) =
+        try
+            match Path.GetDirectoryName(sourcePath) with
+            | null
+            | "" -> Directory.GetCurrentDirectory()
+            | dir -> dir
+        with _ ->
+            Directory.GetCurrentDirectory()
+
+    let runtimeExternsForSourcePath (sourcePath: string) : ExternalFunction list =
+        let ctx = { HostContext.RootDirectory = resolveRootDirectory sourcePath }
+        Registry.all ctx
+
+    let parseProgramFromSourceWithIncludes (sourcePath: string) (sourceText: string) : Program =
+        let rootDirectory = resolveRootDirectory sourcePath
+        IncludeResolver.parseProgramFromSourceWithIncludes rootDirectory sourcePath sourceText
+
+    let inferProgramWithExterns (externs: ExternalFunction list) (program: Program) : TypeInfer.TypedProgram =
+        TypeInfer.inferProgramWithExterns externs program
+
+    let inferProgramWithExternsAndLocalVariableTypes (externs: ExternalFunction list) (program: Program) : TypeInfer.TypedProgram * TypeInfer.LocalVariableTypeInfo list =
+        TypeInfer.inferProgramWithExternsAndLocalVariableTypes externs program
+
+    let inferStdlibWithExternsRaw (externs: ExternalFunction list) : TypeInfer.TypedProgram =
+        TypeInfer.inferProgramWithExternsRaw externs (Stdlib.loadProgram())
+
+    let stdlibProgram () : Program =
+        Stdlib.loadProgram()
+
+    let tryLoadStdlibSourceText (uri: string) : string option =
+        try
+            let parsed = Uri(uri)
+            if not (String.Equals(parsed.Scheme, "fscript-stdlib", StringComparison.OrdinalIgnoreCase)) then
+                None
+            else
+                let fileName = parsed.AbsolutePath.TrimStart('/')
+                let resourceName =
+                    match fileName with
+                    | "Option.fss" -> Some "FScript.Language.Stdlib.Option.fss"
+                    | "List.fss" -> Some "FScript.Language.Stdlib.List.fss"
+                    | "Map.fss" -> Some "FScript.Language.Stdlib.Map.fss"
+                    | _ -> None
+
+                match resourceName with
+                | None -> None
+                | Some name ->
+                    let assembly = typeof<Span>.Assembly
+                    match assembly.GetManifestResourceStream(name) with
+                    | null -> None
+                    | stream ->
+                        use stream = stream
+                        use reader = new StreamReader(stream)
+                        Some(reader.ReadToEnd())
+        with _ ->
+            None

src/FScript.LanguageServer/LspHandlers.fs → src/FScript.CSharpInterop/LanguageServer/LspHandlers.fs

@@ -4,6 +4,7 @@ open System
 open System.IO
 open System.Text.Json.Nodes
 open FScript.Language
+open FScript.CSharpInterop
 
 module LspHandlers =
     open LspModel
@@ -497,12 +498,7 @@ module LspHandlers =
                     | None ->
                         sendCommandError idNode "internal" $"Unable to read source file '{sourcePath}'."
                     | Some sourceText ->
-                        let rootDirectory =
-                            match Path.GetDirectoryName(sourcePath) with
-                            | null
-                            | "" -> "."
-                            | dir -> dir
-                        let program = IncludeResolver.parseProgramFromSourceWithIncludes rootDirectory sourcePath sourceText
+                        let program = InteropServices.parseProgramFromSourceWithIncludes sourcePath sourceText
                         let response = JsonObject()
                         response["ok"] <- JsonValue.Create(true)
                         response["data"] <- AstJson.programToJson sourcePath program
@@ -528,14 +524,9 @@ module LspHandlers =
                     | None ->
                         sendCommandError idNode "internal" $"Unable to read source file '{sourcePath}'."
                     | Some sourceText ->
-                        let rootDirectory =
-                            match Path.GetDirectoryName(sourcePath) with
-                            | null
-                            | "" -> "."
-                            | dir -> dir
-                        let program = IncludeResolver.parseProgramFromSourceWithIncludes rootDirectory sourcePath sourceText
+                        let program = InteropServices.parseProgramFromSourceWithIncludes sourcePath sourceText
                         let runtimeExterns = LspRuntimeExterns.forSourcePath sourcePath
-                        let typedProgram = TypeInfer.inferProgramWithExterns runtimeExterns program
+                        let typedProgram = InteropServices.inferProgramWithExterns runtimeExterns program
                         let response = JsonObject()
                         response["ok"] <- JsonValue.Create(true)
                         response["data"] <- AstJson.typedProgramToJson sourcePath typedProgram
@@ -1103,40 +1094,12 @@ module LspHandlers =
         | _ ->
             LspProtocol.sendResponse idNode None
 
-    let private tryLoadStdlibSourceText (uri: string) =
-        try
-            let parsed = Uri(uri)
-            if not (String.Equals(parsed.Scheme, "fscript-stdlib", StringComparison.OrdinalIgnoreCase)) then
-                None
-            else
-                let fileName = parsed.AbsolutePath.TrimStart('/')
-                let resourceName =
-                    match fileName with
-                    | "Option.fss" -> Some "FScript.Language.Stdlib.Option.fss"
-                    | "List.fss" -> Some "FScript.Language.Stdlib.List.fss"
-                    | "Map.fss" -> Some "FScript.Language.Stdlib.Map.fss"
-                    | _ -> None
-
-                match resourceName with
-                | None -> None
-                | Some name ->
-                    let assembly = typeof<Span>.Assembly
-                    match assembly.GetManifestResourceStream(name) with
-                    | null ->
-                        None
-                    | stream ->
-                        use stream = stream
-                        use reader = new StreamReader(stream)
-                        Some (reader.ReadToEnd())
-        with _ ->
-            None
-
     let handleStdlibSource (idNode: JsonNode) (paramsObj: JsonObject) =
         match tryGetString paramsObj "uri" with
         | None ->
             sendCommandError idNode "internal" "Missing stdlib URI."
         | Some uri ->
-            match tryLoadStdlibSourceText uri with
+            match InteropServices.tryLoadStdlibSourceText uri with
             | Some sourceText ->
                 let response = JsonObject()
                 response["ok"] <- JsonValue.Create(true)

src/FScript.CSharpInterop/LanguageServer/LspRuntimeExterns.fs

@@ -0,0 +1,8 @@
+namespace FScript.LanguageServer
+
+open FScript.Language
+open FScript.CSharpInterop
+
+module LspRuntimeExterns =
+    let forSourcePath (sourcePath: string) : ExternalFunction list =
+        InteropServices.runtimeExternsForSourcePath sourcePath