roslyn.nvim

This is an actively maintained & upgraded fork that interacts with the improved & open-source C# Roslyn language server, meant to replace the old and discontinued OmniSharp. This language server is currently used in the Visual Studio Code C# Extension, which is shipped with the standard C# Dev Kit.

This standalone plugin was necessary because Roslyn uses a non-standard method of initializing communication with the client and requires additional custom integrations, unlike typical LSP setups in Neovim.

⚡️ Requirements

• Neovim >= 0.10.0
• Roslyn language server downloaded locally
• .NET SDK installed and dotnet command available

Demo

roslyn_demo.mp4

📦 Installation

Install the Roslyn language server:

1. Navigate to this feed, search for Microsoft.CodeAnalysis.LanguageServer and download the version matching your OS and architecture.

   For nix users, install roslyn-ls and then you can config this plugin right away.

2. Unzip the downloaded .nupkg and copy the contents of <zip root>/content/LanguageServer/<yourArch> inside:
   • Linux: ~/.local/share/nvim/roslyn
   • Windows: %LOCALAPPDATA%\nvim-data\roslyn

   TIP: You can also specify a custom path to the roslyn folder in the setup function.

3. Check if it's working by running dotnet Microsoft.CodeAnalysis.LanguageServer.dll --version in the roslyn directory.

Note

There's currently an open pull request to add the Roslyn server to mason, which would greatly improve the experience. If you are interested in this, please react to the original comment, but don't spam the thread with unnecessary comments.

Tip

For server compatibility check the roslyn repo

Install the plugin with your preferred package manager:

lazy.nvim

{
    "seblj/roslyn.nvim",
    ft = "cs",
    opts = {
        -- your configuration comes here; leave empty for default settings
    }
}

⚙️ Configuration

The plugin comes with the following defaults:

{
    config = {
        -- Here you can pass in any options that that you would like to pass to `vim.lsp.start`.
        -- Use `:h vim.lsp.ClientConfig` to see all possible options.
        -- The only options that are overwritten and won't have any effect by setting here:
        --     - `name`
        --     - `cmd`
        --     - `root_dir`
    },

    --[[
    -- if you installed `roslyn-ls` by nix, use the following:
      exe = 'Microsoft.CodeAnalysis.LanguageServer',
    ]]
    exe = {
        "dotnet",
        vim.fs.joinpath(vim.fn.stdpath("data"), "roslyn", "Microsoft.CodeAnalysis.LanguageServer.dll"),
    },

    -- NOTE: Set `filewatching` to false if you experience performance problems.
    -- Defaults to true, since turning it off is a hack.
    -- If you notice that the server is _super_ slow, it is probably because of file watching
    -- Neovim becomes super unresponsive on some large codebases, because it schedules the file watching on the event loop.
    -- This issue goes away by disabling this capability, but roslyn will fallback to its own file watching,
    -- which can make the server super slow to initialize.
    -- Setting this option to false will indicate to the server that neovim will do the file watching.
    -- However, in `hacks.lua` I will also just don't start off any watchers, which seems to make the server
    -- a lot faster to initialize.
    filewatching = true,

    -- Optional function that takes an array of solutions as the only argument. Return the solution you
    -- want to use. If it returns `nil`, then it falls back to guessing the solution like normal
    -- Example:
    --
    -- choose_sln = function(sln)
    --     return vim.iter(sln):find(function(item)
    --         if string.match(item, "Foo.sln") then
    --             return item
    --         end
    --     end)
    -- end
    choose_sln = nil,
})

To configure language server specific settings sent to the server, you can modify the config.settings map.

Note

These settings are not guaranteed to be up-to-date and new ones can appear in the future. Aditionally, not not all settings are shown here, but only the most relevant ones for Neovim. For a full list, visit this unit test from the vscode extension and look especially for the ones which don't have vsCodeConfiguration: null.

Background Analysis

csharp|background_analysis

These settings control the scope of background diagnostics.

• background_analysis.dotnet_analyzer_diagnostics_scope
  Scope of the background analysis for .NET analyzer diagnostics.
  Expected values: openFiles, fullSolution, none

• background_analysis.dotnet_compiler_diagnostics_scope
  Scope of the background analysis for .NET compiler diagnostics.
  Expected values: openFiles, fullSolution, none

Code Lens

csharp|code_lens

These settings control the LSP code lens.

• dotnet_enable_references_code_lens
  Enable code lens references.
  Expected values: true, false

• dotnet_enable_tests_code_lens
  Enable tests code lens.
  Expected values: true, false

Tip

You must refresh the code lens yourself. Check :h vim.lsp.codelens.refresh() and the example autocmd.

Completions

csharp|completion

These settings control how the completions behave.

• dotnet_provide_regex_completions
  Show regular expressions in completion list.
  Expected values: true, false

• dotnet_show_completion_items_from_unimported_namespaces
  Enables support for showing unimported types and unimported extension methods in completion lists.
  Expected values: true, false

• dotnet_show_name_completion_suggestions
  Perform automatic object name completion for the members that you have recently selected.
  Expected values: true, false

Inlay hints

csharp|inlay_hints

These settings control what inlay hints should be displayed.

• csharp_enable_inlay_hints_for_implicit_object_creation
  Show hints for implicit object creation.
  Expected values: true, false

• csharp_enable_inlay_hints_for_implicit_variable_types
  Show hints for variables with inferred types.
  Expected values: true, false

• csharp_enable_inlay_hints_for_lambda_parameter_types
  Show hints for lambda parameter types.
  Expected values: true, false

• csharp_enable_inlay_hints_for_types
  Display inline type hints.
  Expected values: true, false

• dotnet_enable_inlay_hints_for_indexer_parameters
  Show hints for indexers.
  Expected values: true, false

• dotnet_enable_inlay_hints_for_literal_parameters
  Show hints for literals.
  Expected values: true, false

• dotnet_enable_inlay_hints_for_object_creation_parameters
  Show hints for 'new' expressions.
  Expected values: true, false

• dotnet_enable_inlay_hints_for_other_parameters
  Show hints for everything else.
  Expected values: true, false

• dotnet_enable_inlay_hints_for_parameters
  Display inline parameter name hints.
  Expected values: true, false

• dotnet_suppress_inlay_hints_for_parameters_that_differ_only_by_suffix
  Suppress hints when parameter names differ only by suffix.
  Expected values: true, false

• dotnet_suppress_inlay_hints_for_parameters_that_match_argument_name
  Suppress hints when argument matches parameter name.
  Expected values: true, false

• dotnet_suppress_inlay_hints_for_parameters_that_match_method_intent
  Suppress hints when parameter name matches the method's intent.
  Expected values: true, false

Tip

These won't have any effect if you don't enable inlay hints in your config. Check :h vim.lsp.inlay_hint.enable().

Symbol search

csharp|symbol_search

This setting controls how the language server should search for symbols.

• dotnet_search_reference_assemblies
  Search symbols in reference assemblies.
  Expected values: true, false

Example:

opts = {
    config = {
        settings = {
            ["csharp|inlay_hints"] = {
                csharp_enable_inlay_hints_for_implicit_object_creation = true,
                csharp_enable_inlay_hints_for_implicit_variable_types = true,
                csharp_enable_inlay_hints_for_lambda_parameter_types = true,
                csharp_enable_inlay_hints_for_types = true,
                dotnet_enable_inlay_hints_for_indexer_parameters = true,
                dotnet_enable_inlay_hints_for_literal_parameters = true,
                dotnet_enable_inlay_hints_for_object_creation_parameters = true,
                dotnet_enable_inlay_hints_for_other_parameters = true,
                dotnet_enable_inlay_hints_for_parameters = true,
                dotnet_suppress_inlay_hints_for_parameters_that_differ_only_by_suffix = true,
                dotnet_suppress_inlay_hints_for_parameters_that_match_argument_name = true,
                dotnet_suppress_inlay_hints_for_parameters_that_match_method_intent = true,
            },
            ["csharp|code_lens"] = {
                dotnet_enable_references_code_lens = true,
            },
        }
    }
}

🚀 Other usage

• If you have multiple solutions, this plugin tries to guess which one to use. You can change the target with the :CSTarget command.
• The current solution is always stored in vim.g.roslyn_nvim_selected_solution. You can use this, for example, to display the current solution in your statusline.