nvim-lspconfig/lsp/rust_analyzer.lua

---@brief
---
--- https://github.com/rust-lang/rust-analyzer
---
--- rust-analyzer (aka rls 2.0), a language server for Rust
---
---
--- See [docs](https://rust-analyzer.github.io/book/configuration.html) for extra settings. The settings can be used like this:
--- ```lua
--- vim.lsp.config('rust_analyzer', {
---   settings = {
---     ['rust-analyzer'] = {
---       diagnostics = {
---         enable = false;
---       }
---     }
---   }
--- })
--- ```
---
--- Note: do not set `init_options` for this LS config, it will be automatically populated by the contents of settings["rust-analyzer"] per
--- https://github.com/rust-lang/rust-analyzer/blob/eb5da56d839ae0a9e9f50774fa3eb78eb0964550/docs/dev/lsp-extensions.md?plain=1#L26.

local function reload_workspace(bufnr)
  local clients = vim.lsp.get_clients { bufnr = bufnr, name = 'rust_analyzer' }
  for _, client in ipairs(clients) do
    vim.notify 'Reloading Cargo Workspace'
    ---@diagnostic disable-next-line:param-type-mismatch
    client:request('rust-analyzer/reloadWorkspace', nil, function(err)
      if err then
        error(tostring(err))
      end
      vim.notify 'Cargo workspace reloaded'
    end, 0)
  end
end

local function is_library(fname)
  local user_home = vim.fs.normalize(vim.env.HOME)
  local cargo_home = os.getenv 'CARGO_HOME' or user_home .. '/.cargo'
  local registry = cargo_home .. '/registry/src'
  local git_registry = cargo_home .. '/git/checkouts'

  local rustup_home = os.getenv 'RUSTUP_HOME' or user_home .. '/.rustup'
  local toolchains = rustup_home .. '/toolchains'

  for _, item in ipairs { toolchains, registry, git_registry } do
    if vim.fs.relpath(item, fname) then
      local clients = vim.lsp.get_clients { name = 'rust_analyzer' }
      return #clients > 0 and clients[#clients].config.root_dir or nil
    end
  end
end

---@type vim.lsp.Config
return {
  cmd = { 'rust-analyzer' },
  filetypes = { 'rust' },
  root_dir = function(bufnr, on_dir)
    local fname = vim.api.nvim_buf_get_name(bufnr)
    local reused_dir = is_library(fname)
    if reused_dir then
      on_dir(reused_dir)
      return
    end

    local cargo_crate_dir = vim.fs.root(fname, { 'Cargo.toml' })
    local cargo_workspace_root

    if cargo_crate_dir == nil then
      on_dir(
        vim.fs.root(fname, { 'rust-project.json' })
          or vim.fs.dirname(vim.fs.find('.git', { path = fname, upward = true })[1])
      )
      return
    end

    local cmd = {
      'cargo',
      'metadata',
      '--no-deps',
      '--format-version',
      '1',
      '--manifest-path',
      cargo_crate_dir .. '/Cargo.toml',
    }

    vim.system(cmd, { text = true }, function(output)
      if output.code == 0 then
        if output.stdout then
          local result = vim.json.decode(output.stdout)
          if result['workspace_root'] then
            cargo_workspace_root = vim.fs.normalize(result['workspace_root'])
          end
        end

        on_dir(cargo_workspace_root or cargo_crate_dir)
      else
        vim.schedule(function()
          vim.notify(('[rust_analyzer] cmd failed with code %d: %s\n%s'):format(output.code, cmd, output.stderr))
        end)
      end
    end)
  end,
  capabilities = {
    experimental = {
      serverStatusNotification = true,
      commands = {
        commands = {
          'rust-analyzer.showReferences',
          'rust-analyzer.runSingle',
          'rust-analyzer.debugSingle',
        },
      },
    },
  },
  settings = {
    ['rust-analyzer'] = {
      lens = {
        debug = { enable = true },
        enable = true,
        implementations = { enable = true },
        references = {
          adt = { enable = true },
          enumVariant = { enable = true },
          method = { enable = true },
          trait = { enable = true },
        },
        run = { enable = true },
        updateTest = { enable = true },
      },
    },
  },
  before_init = function(init_params, config)
    -- See https://github.com/rust-lang/rust-analyzer/blob/eb5da56d839ae0a9e9f50774fa3eb78eb0964550/docs/dev/lsp-extensions.md?plain=1#L26
    if config.settings and config.settings['rust-analyzer'] then
      init_params.initializationOptions = config.settings['rust-analyzer']
    end
    ---@param command table{ title: string, command: string, arguments: any[] }
    vim.lsp.commands['rust-analyzer.runSingle'] = function(command)
      local r = command.arguments[1]
      local cmd = { 'cargo', unpack(r.args.cargoArgs) }
      if r.args.executableArgs and #r.args.executableArgs > 0 then
        vim.list_extend(cmd, { '--', unpack(r.args.executableArgs) })
      end

      local proc = vim.system(cmd, { cwd = r.args.cwd })

      local result = proc:wait()

      if result.code == 0 then
        vim.notify(result.stdout, vim.log.levels.INFO)
      else
        vim.notify(result.stderr, vim.log.levels.ERROR)
      end
    end
  end,
  on_attach = function(_, bufnr)
    vim.api.nvim_buf_create_user_command(bufnr, 'LspCargoReload', function()
      reload_workspace(bufnr)
    end, { desc = 'Reload current cargo workspace' })
  end,
}