C# Roslyn Extension for Zed

A Zed editor extension providing C# language support via OmniSharp-Roslyn and netcoredbg debugger.

Features

• Code completion, go-to-definition, find references, rename symbol
• Diagnostics and code analysis
• Solution file detection (.sln, .slnx, .slnf)
• MSBuild integration
• Unity project support - automatic detection and configuration
• Debugging support via netcoredbg
• Auto-downloads OmniSharp-Roslyn and netcoredbg on first use
• Supports custom OmniSharp installations via PATH

Known Limitations

• Go-to-definition on BCL (Base Class Library) types currently not working
• Some cross-project navigation may be limited

Installation

This extension is currently in development and not available in the Zed extension registry.

To install:

1. Clone this repository
2. Open Zed and run: zed: extensions: install dev extension
3. Select the cloned csharp_roslyn directory
4. Restart Zed

Setup

Basic Usage

The extension works out of the box! Simply open a C# project with a .sln file and start coding.

Unity Projects

For Unity projects, see Unity Support Guide for setup instructions.

Quick start:

1. Generate project files in Unity: Edit → Preferences → External Script Editor → "Regenerate project files"
2. Open Unity project folder in Zed
3. Extension automatically detects Unity projects and configures OmniSharp appropriately

Optional: Specify Solution Path

If auto-detection doesn't find your solution file, specify it in your Zed settings (Cmd+, / Ctrl+,):

{
  "language_servers": {
    "omnisharp-roslyn": {
      "initialization_options": {
        "solution": "/absolute/path/to/your/solution.sln"
      }
    }
  }
}

Optional: Use Custom OmniSharp Installation

{
  "language_servers": {
    "omnisharp-roslyn": {
      "enabled": true,
      "initialization_options": {
        "solution": "/absolute/path/to/your/solution.sln"
      }
    }
  }
}

Debugging

The extension supports automatic debug configuration generation from tasks or manual configuration.

Option 1: Tasks with Auto-Generated Debug Config (Recommended)

Create .zed/tasks.json in your project root:

[
  {
    "label": "Run MyApp",
    "command": "dotnet",
    "args": ["run", "--project", "src/MyApp/MyApp.csproj"],
    "use_new_terminal": false
  },
  {
    "label": "Build MyApp",
    "command": "dotnet",
    "args": ["build", "src/MyApp/MyApp.csproj"],
    "use_new_terminal": false
  }
]

The extension automatically generates debug configurations from your dotnet run tasks. Simply select the task from the debug panel and start debugging!

Option 2: Manual Debug Configuration

Create .zed/debug.json in your project root:

[
  {
    "label": "Debug MyApp",
    "adapter": "netcoredbg",
    "request": "launch",
    "program": "$ZED_WORKTREE_ROOT/src/MyApp/bin/Debug/{targetFramework}/MyApp.dll",
    "args": [],
    "cwd": "$ZED_WORKTREE_ROOT",
    "stopAtEntry": false,
    "console": "internalConsole"
  }
]

Note: The {targetFramework} placeholder (e.g., net8.0, net9.0) is automatically detected from your .csproj file at debug time.

Debug Configuration Options

• program: Path to the .NET DLL to debug (use $ZED_WORKTREE_ROOT for workspace root)
• args: Array of command-line arguments
• cwd: Working directory
• env: Environment variables object
• stopAtEntry: Break at program entry point (default: false)
• console: "internalConsole", "integratedTerminal", or "externalTerminal"

Example: Debug with Arguments

{
  "label": "Debug with Args",
  "adapter": "netcoredbg",
  "request": "launch",
  "program": "$ZED_WORKTREE_ROOT/bin/Debug/{targetFramework}/MyApp.dll",
  "args": ["--verbose", "input.txt"],
  "env": {
    "ASPNETCORE_ENVIRONMENT": "Development"
  },
  "cwd": "$ZED_WORKTREE_ROOT"
}

Troubleshooting

Debug Logging

For detailed troubleshooting information, enable debug logging in your Zed settings:

{
  "lsp": {
    "csharp_roslyn": {
      "initialization_options": {
        "enable_debug_logging": true
      }
    }
  }
}

Debug messages appear in the terminal when running Zed with zed . --foreground. Extension logs do not appear in Zed's main log file due to WASM sandbox limitations.

Messages are prefixed with [csharp_roslyn] and show:

• Unity project detection status
• Solution file discovery attempts
• OmniSharp download progress
• Debugger setup steps
• Configuration decisions

Language Server Won't Start

• Extension auto-downloads OmniSharp-Roslyn on first use
• Cache location: ~/.cache/zed/extensions/csharp_roslyn/cache/ (Linux/macOS) or %LOCALAPPDATA%\Zed\extensions\csharp_roslyn\cache\ (Windows)
• Enable debug logging (above) for detailed diagnostics
• Check terminal output when running with zed . --foreground for debug messages
• Manually download from: https://github.com/OmniSharp/omnisharp-roslyn/releases

Debugger Issues

• Extension auto-downloads netcoredbg on first use
• Verify program path exists and build completed successfully
• Ensure Debug configuration (not Release)
• Enable debug logging (above) for detailed diagnostics
• Check logs: Help → View Logs

No Solution File Detected

• Place .sln file in workspace root, or
• Manually specify solution path in settings (see Setup section above)

Development

Building

cargo build --target wasm32-wasip2 --release

Installing Dev Build

cp target/wasm32-wasip2/release/csharp_roslyn.wasm ~/Library/Application\ Support/Zed/extensions/installed/csharp_roslyn/extension.wasm

License

MIT License

Links

• OmniSharp-Roslyn: https://github.com/OmniSharp/omnisharp-roslyn
• netcoredbg: https://github.com/Samsung/netcoredbg
• Issues: https://github.com/marcptrs/csharp-roslyn/issues