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ramboe 1c74f3265b update readme		2025-12-11 11:11:38 +01:00
README.md	update readme	2025-12-11 11:11:38 +01:00

README.md

Neovim + C# Updates: fixing roslyn.nvim when rzls is no more

Intro

In the past it needed two lsp plugins

roslyn.nvim - .cs
rzls.nvim - .razor

If you're using nvim and Mason, you might have seen this screen recently:

This is reflected on github as follows:

https://github.com/seblyng/roslyn.nvim?tab=readme-ov-file#razorcshtml-support

https://github.com/tris203/rzls.nvim?tab=readme-ov-file#composing-the-command-for-roslyn

unfortunately it's not that easy

https://github.com/seblyng/roslyn.nvim/issues/273

Setup As Recommended

dotnet-sdk-10.0

Make sure dotnet 10 is installed for the updated roslyn to work, otherwise we get a 150 from neovim when trying to open a .cs or .razor file:

[ERROR][2025-12-10 12:11:35] ...p/_transport.lua:36 "rpc" "roslyn" "stderr" "You must install or update .NET to run this application.\n\nApp: /home/ramboe/.local/share/nvim/mason/packages/roslyn/libexec/Microsoft.CodeAnalysis.LanguageServer.dll\nArchitecture: x64\nFramework: 'Microsoft.NETCore.App', version '10.0.0-rc.2.25502.107' (x64)\n.NET location: /usr/lib64/dotnet/\n\nThe following frameworks were found:\n 9.0.11 at [/usr/lib64/dotnet/shared/Microsoft.NETCore.App]\n\nLearn more:\nhttps://aka.ms/dotnet/app-launch-failed\n\nTo install missing framework, download:\nhttps://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=10.0.0-rc.2.25502.107&arch=x64&rid=fedora.41-x64&os=fedora.41\n"

kick out anything `rzls`

When done correctly, your lua/configs/lspconfig.lua looks like this

vim.lsp.config("roslyn", {})

And your lua/plugins/init.lua looks like this

  {
    "seblyng/roslyn.nvim",
    ---@module 'roslyn.config'
    ---@type RoslynNvimConfig
    ft = { "cs", "razor" },
    lazy = false
  },

If you encounter issues, like "roslyn: -32000: Attempted to retrieve a Document but a TextDocument was found instead" - this will be solved further in this article

In Case of Any Problems

Create a new blazor project

cd ~/Documents && \
dotnet new blazor -n MyBlazor
cd MyBlazor && \
dotnet build

make sure to adjust the .csproj so it builds:

<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup>
    <AllowMissingPrunePackageData>true</AllowMissingPrunePackageData>
    ...
  </PropertyGroup>
</Project>

then witness the shards:

Program.cs - "Using directive is unnecessary."

Counter.razor - "roslyn: -32000: Attempted to retrieve a Document but a TextDocument was found instead."

This is because roslyn can't locate the DLLs necessary for .razor files, even when they are properly installed with mason:

Composing cmd Explicitely

Following the docs results into the following plugins/init.lua:

  {
    "seblyng/roslyn.nvim",
    ---@module 'roslyn.config'
    ---@type RoslynNvimConfig
    ft = { "cs", "razor" },
    lazy = false,
    config = function()
local rzls_path = vim.fn.expand("$MASON/packages/roslyn/libexec/.razorExtension")

      local cmd = {
        "roslyn",
        "--stdio",
        "--logLevel=Information",
        "--extensionLogDirectory=" .. vim.fs.dirname(vim.lsp.get_log_path()),
        "--razorSourceGenerator=" .. vim.fs.joinpath(rzls_path, "Microsoft.CodeAnalysis.Razor.Compiler.dll"),
        "--razorDesignTimePath=" .. vim.fs.joinpath(rzls_path, "Targets", "Microsoft.NET.Sdk.Razor.DesignTime.targets"),
        "--extension=" .. vim.fs.joinpath(rzls_path, "Microsoft.VisualStudioCode.RazorExtension.dll"),
      }

      vim.lsp.config("roslyn", {
        cmd = cmd,
      })
    end
  },

Where $MASON stands for ~/.local/share/nvim/mason (on linux) which would result in the following absolute path

~/.local/share/nvim/mason/packages/roslyn/libexec/.razorExtension

unfortunately working with $MASON like this

local rzls_path = vim.fn.expand("$MASON/packages/rzls/libexec")

doesn't change anything, we still get the same errors. Problem: $MASON is not loaded until neovim is full initialised;

Solution

We get the mason root path directly from the mason.settings module, instead of the $MASON environment variable:

-- lua/configs/lspconfig.lua  

-- ROSLYN (+razor support)
local mason_root = require("mason.settings").current.install_root_dir
local rzls_path = vim.fn.expand(mason_root .. "/packages/roslyn/libexec/.razorExtension")

vim.lsp.config("roslyn", {
  --  https://github.com/tris203/rzls.nvim?tab=readme-ov-file#composing-the-command-for-roslyn
  cmd = {
    "roslyn",
    "--stdio",
    "--logLevel=Information",
    "--extensionLogDirectory=" .. vim.fs.dirname(vim.lsp.get_log_path()),
    "--razorSourceGenerator=" .. vim.fs.joinpath(rzls_path, "Microsoft.CodeAnalysis.Razor.Compiler.dll"),
    "--razorDesignTimePath=" .. vim.fs.joinpath(rzls_path, "Targets", "Microsoft.NET.Sdk.Razor.DesignTime.targets"),
    "--extension=" .. vim.fs.joinpath(rzls_path, "Microsoft.VisualStudioCode.RazorExtension.dll"),
  },
})
-- END ROSLYN

Actually..

You don't even need the full cmd specification, it is enough to load the install_root_dir, this will then make $MASON available.

Those to lines inside the lua/configs/lspconfig.lua are enough to make everything work.

-- ROSLYN (+razor support)
local mason_root = require("mason.settings").current.install_root_dir

vim.lsp.config("roslyn", {})
-- END ROSLYN

while your lua/plugins/init.lua can be as slim as this

  {
    "seblyng/roslyn.nvim",
    ---@module 'roslyn.config'
    ---@type RoslynNvimConfig
    ft = { "cs", "razor" }
  },