Roll out LSP semantic highlighting in Visual Studio by abonie · Pull Request #20965 · dotnet/fsharp

abonie · 2026-11-11T10:52:54Z

Description

Integration branch for rolling out LSP-based semantic highlighting in Visual Studio. The LSP server serves textDocument/semanticTokens again, follows the active project context so highlighting stays correct after switching target frameworks, and exposes project contexts and code actions. LSP diagnostics stay off by default in favor of the existing extension. Telemetry is shared between legacy and LSP highlighting so the two paths can be compared during rollout. Also moves the F# LSP extension to VS Extensibility 18.5 / .NET 10.

Checklist

Test cases added
Performance benchmarks added in case of performance changes
Release notes entry updated

github-actions · 2026-11-11T10:53:06Z

✅ Release notes checked

✅ Found changes and release notes in following paths:

Change path Release notes path Description

`src/Compiler` docs/release-notes/.FSharp.Compiler.Service/11.0.200.md

- Merge LSP VSIX into the old VSIX (CreateVsixContainer, AssemblyVSIXSubPath) - Remove unfinished semantic tokens endpoint from LanguageFeaturesHandler - Remove SemanticTokensOptions from CapabilitiesManager and VS provider - Remove TokenTypes module from FSharpRequestContext - Refactor ClassificationService: simplify classification logic - Remove unused WorkspaceExtensions and SemanticHighlighting setting - Rename config field SemanticHighlighting -> CodeActions (default false) - Bump LSP protocol packages to 17.13.9, add Protocol.Extensions Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add ILspTelemetry abstraction with NullTelemetry default - Rename ToLspDiagnostic -> ToVsDiagnostic with severity mapping and project info - Add makeProjectContextId and snapshotsToProjectInfos shared helpers - Add VSExtensionConverters to server serializer and formatter - Expose GetProjectSnapshotsForFile in FSharpWorkspaceQuery - Respect fsharp.getDiagnosticsFrom unified setting in DocumentDiagnosticAnalyzer - Refactor LSP tests: extract ProtocolHelpers, add diagnostics tests Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add ProjectContextsHandler for the _vs_getProjectContexts LSP endpoint - Register handler in FSharpLanguageServer DI container - Remove duplicate project contexts handler from VsDiagnosticsHandler - Add ProjectContextsProtocolTests Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add CodeActionHandler with F# code fixes (quickfix actions) - Register handler in FSharpLanguageServer and CapabilitiesManager - Add CodeActionProvider capability to VS extension - Enable CodeActions feature flag by default - Add CodeActionProtocolTests Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add VsTelemetryReporter for VS-side telemetry - Instrument DocumentStateHandler with open/close events Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Add FSharpApexTestBase for VS integration test scaffolding - Add ErrorListDiagnosticsTests and LightBulbCodeActionTests - Wire VsTelemetryReporter into VS extension server provider - Fix whitespace and ordering in project files Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Set the effective default of fsharp.getDiagnosticsFrom to 'old' so the in-proc (old) extension serves diagnostics and the LSP diagnostics endpoint stays off by default (but remains switchable to lsp/both). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Stacks the semantic-tokens-rollout work on top of the diagnostics rollout branch: adds the textDocument/semanticTokens endpoint and disables the LSP diagnostics endpoint (the in-proc extension stays authoritative for diagnostics until that rollout graduates). This reconstructs the tree of the original semantic-tokens-rollout-prep branch (preserved as backup) on top of lsp-diagnostics-rollout. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove duplicate inline package pins, centralize LSP and Apex test dependencies, and adapt tokenizer and classification regression tests to current main APIs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: df139595-f788-456b-908f-83de4c89548c

Restore Visual Studio Extensibility 17.14.40313 and track CLaSP with the Roslyn dependency flow. Migrate LSP transports and protocol tests to System.Text.Json, adapting framework lifecycle and logger APIs while preserving VS extension metadata. Prefer CLI event resolutions over synthesized add/remove members, add instance/static event regression coverage, and include the previously untracked project-context tests. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: df139595-f788-456b-908f-83de4c89548c

Forward Roslyn active document contexts to the LSP server, resolve compiler output identities, and refresh classifications without stale responses. Add alternating-framework and refresh-retry protocol coverage. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 5a0d205e-f647-4704-a3f6-1dcd028a0b44

Upgrade the LSP client to 18.12.55 and protocol packages to 18.12.5 to resolve the assembly version conflict. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: a8b27f92-13b7-400d-8af8-1f85b6162e46

Align dependent packages, require Visual Studio 18.5, and update VSIX metadata paths. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: a8b27f92-13b7-400d-8af8-1f85b6162e46

Track eligible rollout exposure and provider outcomes, apply shared consent with the Microsoft-internal override, and keep policy forwarding alive beyond document views. Add bounded startup retries, regression tests, and telemetry documentation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 6449d63c-e5d8-4984-b4f5-8330252348fc

abonie

🤖🕵️ AI review — verify independently.

Disable the provider before returning no connection for legacy selections so VS does not repeatedly activate it. Keep exposure telemetry but avoid per-view LSP context wiring for the legacy provider. Retain disabled diagnostics and code-action fixtures as ignored MSTest classes, discover vstest via vswhere, and build/run the LSP integration project through the shared Apex path with its runsettings. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Insert fun before lambda arguments, validate writable assignment targets, preserve implemented interface members and document newlines, and rename all parameter uses to match signatures. Propagate cancellation and report named code-fix failures. Disable code actions by default and opt protocol tests in explicitly. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Lift synchronous fixes explicitly and keep all registrations in one flat list, including interface implementation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

…ough VMR Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

… LSP Skip legacy semantic classification only for open host-workspace documents when LSP is selected. Keep other workspaces, including preview and miscellaneous files, eligible without adding a server-failure fallback. Report fallback_only state and document the open-document FAR limitation. Validation: - .\Build.cmd -c Debug: passed, 0 warnings, 0 errors (after clean artifacts). - dotnet test --project vsintegration\tests\FSharp.Editor.Tests\FSharp.Editor.Tests.fsproj -c Debug --no-build --filter-class '*Classification*' '*Telemetry*': 233 passed, 0 failed. - Same test command with --filter-class '*SemanticClassificationPolicyTests*': 13 passed, 0 failed. - dotnet fantomas --check on all three touched F# files: passed. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Treat Host and MiscellaneousFiles as LSP-rendered editor workspaces when open. Closed documents and other workspace kinds remain eligible for legacy classification. Update predicate/provider tests and fallback docs. Validation: - .\Build.cmd -c Debug: passed, 0 warnings, 0 errors. - dotnet test --project vsintegration\tests\FSharp.Editor.Tests\FSharp.Editor.Tests.fsproj -c Debug --no-build --filter-class '*Classification*' '*Telemetry*': 235 passed, 0 failed, 0 skipped. - dotnet fantomas and --check on both touched F# files: passed. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

abonie

🤖🕵️ AI re-review — verify independently.

abonie · 2026-11-12T16:14:00Z

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>$(FSharpNetCoreProductTargetFramework)-windows8.0</TargetFramework>


🤖🕵️ Every Windows job in build 1677808 fails in VerifyAssemblyVersionsAndSymbols (15 jobs, including EndToEndBuildTests and MockOfficial). AssemblyCheck requires an embedded PDB in every FSharp*.dll, and this test assembly gets DebugType=portable from tests/Directory.Build.props and isn't listed in buildtools/AssemblyCheck/SkipVerifyEmbeddedPdb.txt.

The following assemblies don't have an embedded pdb D:\a\_work\1\s\artifacts\bin\FSharp.VisualStudio.Extension.Tests\Release\net11.0-windows8.0\FSharp.VisualStudio.Extension.Tests.dll Command failed to execute with exit code 1: ... AssemblyCheck.dll

Fix: add the DLL to the skip list, as the other test projects are.

FSharp.VisualStudio.Extension.Tests.dll

abonie · 2026-11-12T16:14:00Z

 let otherProjects =
    [// project path                                                                         batch  batched platform, unbatched platform
        "tests/FSharp.Build.UnitTests/FSharp.Build.UnitTests.fsproj",                        1,     "all",     "all"
+        "tests/FSharp.Compiler.LanguageServer.Tests/FSharp.Compiler.LanguageServer.Tests.fsproj", 1, "coreclr", "coreclr"


🤖🕵️ Linux Batch1 and MacOS Batch1 now fail as soon as dotnet test reaches this project: global.json selects Microsoft.Testing.Platform, and the SDK classifies this project as VSTest. The project has never run in this batch before (it was excluded until f465972), so the runner setup needs fixing before it can be batched.

global.json defines test runner to be Microsoft.Testing.Platform. All projects must use that test runner. The following test projects are using VSTest test runner: FSharp.Compiler.LanguageServer.Tests.fsproj

abonie · 2026-11-12T16:14:00Z

+    static member ShouldClassify(provider, workspaceKind, isOpenDocument) =
+        let isLspEditorWorkspace =
+            workspaceKind = WorkspaceKind.Host
+            || workspaceKind = WorkspaceKind.MiscellaneousFiles


🤖🕵️ Under lsp, open standalone scripts and loose .fs files lose semantic colouring. This predicate skips them, and SingleFileWorkspaceMap puts them in an "F# Miscellaneous Files" project. But the server only learns about .fsproj projects, so GetProjectSnapshotForFile returns None, GetSemanticClassification returns None, and only lexical tokens come back. The "file not in any project" protocol test only checks that the data is well-formed.

// Script.fsx opened with File > Open, not in any project type Widget() = class end let w = Widget() // Widget and w get no type/value colouring; only keywords and literals

Fix: keep legacy classification for document.Project.IsFSharpMiscellaneousOrMetadata (Common/Extensions.fs:67) until the server serves script projects.

github-project-automation Bot added this to F# Compiler and Tooling Nov 11, 2026

github-project-automation Bot moved this to New in F# Compiler and Tooling Nov 11, 2026

abonie and others added 18 commits November 11, 2026 11:54

Add telemetry instrumentation for LSP server

9e424bf

- Add VsTelemetryReporter for VS-side telemetry - Instrument DocumentStateHandler with open/close events Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add VS local development and MCP testing skills

80fa009

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Add copilot skills for VS integration

242b7ac

Use project context when querying workspace

bcf3fbd

Upgrade F# LSP extension to Extensibility 18.5 and .NET 10

636b4f2

Align dependent packages, require Visual Studio 18.5, and update VSIX metadata paths. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: a8b27f92-13b7-400d-8af8-1f85b6162e46

Bump VS Extensibility packages

d5b6a4f

abonie force-pushed the lsp/semantic-tokens branch from 60112fb to c236379 Compare November 11, 2026 11:07

abonie added 2 commits November 11, 2026 12:13

Rename vs-mcp-testing-tools dir

810dc71

Run fantomas

ec21061

abonie commented Nov 11, 2026

View reviewed changes

abonie and others added 5 commits November 11, 2026 15:22

Bound semantic token processing by line and honor cancellation

63950d7

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Merge semantic tokens perf and cancellation fixes

8e1c5bd

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Merge VS provider gating, settings and Apex test fixes

2525ac1

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

abonie and others added 10 commits November 11, 2026 15:37

Clarify synchronous code-fix registration

a1e96f8

Lift synchronous fixes explicitly and keep all registrations in one flat list, including interface implementation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Merge LSP code action fixes

7a5c6ff

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Update workspace API baseline, run LSP tests in CI, and track STJ thr…

f465972

…ough VMR Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Merge FCS surface area, LSP test CI and System.Text.Json tracking fixes

a95c6ac

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Merge legacy classification fallback for documents LSP does not render

a8e0199

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 0c106877-ba3b-418c-9716-697da9c76300

Require net10.0 in vsixmanifest

ad7053d

Don't try to start the server when LSP is off

d29393e

Remove unnecessary pragmas for now stable apis

a0f24cd

abonie commented Nov 12, 2026

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Roll out LSP semantic highlighting in Visual Studio - #20965

Roll out LSP semantic highlighting in Visual Studio#20965
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abonie commented Nov 11, 2026

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