How to configure pylsp when using mason and mason-lspconfig in Neovim?

Question

I want to configure my Python language server (pylsp) in Neovim in a Lua config (init.lua). I just transitioned from a Vimscript to a Lua config with basically zero Lua knowledge and this is causing some headaches. Additionally, I took as my starting point the kickstart.nvim repo so lsp is handled by mason which also is a new tool for me.

The basic setup of pylsp is handled via:

local servers = {
  pylsp = {},

  sumneko_lua = {
    Lua = {
      workspace = { checkThirdParty = false },
      telemetry = { enable = false },
    },
  },
}

-- Setup neovim lua configuration
require('neodev').setup()
--
-- nvim-cmp supports additional completion capabilities, so broadcast that to servers
local capabilities = vim.lsp.protocol.make_client_capabilities()
capabilities = require('cmp_nvim_lsp').default_capabilities(capabilities)

-- Setup mason so it can manage external tooling
require('mason').setup()

-- Ensure the servers above are installed
local mason_lspconfig = require 'mason-lspconfig'

mason_lspconfig.setup {
  ensure_installed = vim.tbl_keys(servers),
}

mason_lspconfig.setup_handlers {
  function(server_name)
    require('lspconfig')[server_name].setup {
      capabilities = capabilities,
      on_attach = on_attach,
      settings = servers[server_name],
    }
  end,
}

Based on the sumneko_lua config (4th line in the above code block) as well as e.g. https://github.com/neovim/nvim-lspconfig/blob/master/doc/server_configurations.md#pylsp I tried to e.g. configure pycodestyle by replacing:

  pylsp = {},

with:

  pylsp = {
    plugins = {
      pycodestyle = {
        ignore = {'W391'},
        maxLineLength = 100
      }
    }
  },

However the changes seem to not have any effect. When I open a Lua file and run inside nvim:

:lua print(vim.inspect(vim.lsp.get_active_clients()))

I see that the sumneko_lua variable values are altered. However, when I run the same command in a Python file, I don't even see the 'plugins' and any fields of interest.

So, what am I doing wrong and how can I fix it? Eventually I'm interested in trying out 3rd party plugins listed here but to do that I would have to disable some of those active by default in the config.

Answer 1

I solved it. You actually need to add a seemingly redundant pylsp key, like:

  pylsp = {
    pylsp = {
        plugins = {
          pycodestyle = {
            ignore = {'W391'},
            maxLineLength = 100
          }
        }
    }
  },

This is because the top-level pylsp refers to the name of the LSP itself, but all the settings for pylsp start with pylsp. (similarly, this is why you see sumneko_lua = { Lua = { ... } } in the defaults).