Roslyn diagnostics in the alpha VS Code extension.

Diagnostics

SharpLsp routes C# compiler errors, warnings, and Roslyn analyzer diagnostics through the C# sidecar. The current website shows the VS Code extension state; F# diagnostics are still in progress.

How It Works

Editor ←→ Rust LSP Host ←→ C# Sidecar
  ↑            ↑                ↑
Problems   publishDiagnostics  Roslyn
window     notifications       GetDiagnostics()

1. Document change — editor sends textDocument/didChange, Rust host updates VFS and tree-sitter
2. Debounce — changes are coalesced over a 150ms window (configurable)
3. Dispatch — Rust host sends a workspace/diagnostics request to the C# sidecar
4. Analysis — Roslyn runs full semantic analysis on the affected scope
5. Publish — results are mapped to LSP Diagnostic objects and pushed to the editor

Note: Diagnostics are currently C# only. F# diagnostics via FCS are not yet implemented.

Analysis Scope

Solution-wide analysis is part of the SharpLsp direction. The alpha extension is still being hardened, so treat diagnostics behavior as active development rather than a beta stability guarantee.

Diagnostic Categories

Compiler Diagnostics

Analyzer Diagnostics

• Built-in Roslyn analyzers — IDE0001–IDE0090, CA1000–CA2000 code quality rules
• .editorconfig rules — code style enforcement mapped from .editorconfig severity
• Third-party NuGet analyzers — StyleCop, SonarAnalyzer, and any <Analyzer> reference

Live Squiggles

Diagnostics are pushed in three situations:

• On document change — re-analysis after the debounce window
• On project change — re-analysis when .csproj / .fsproj changes
• On solution load — full solution scan, streamed incrementally

Configuration

# sharplsp.toml
[diagnostics]
# Run Roslyn analyzers (not just compiler errors)
analyzers_enabled = true

# Analyze all files in the solution, not just open ones
solution_wide_analysis = true

# Restrict analysis to specific projects by name (empty = all)
project_filter = []

Project Filter

Narrow the scope for large monorepos:

[diagnostics]
project_filter = ["MyApp.Core", "MyApp.Api"]

Performance Targets

Severity Mapping