Configure the efm language server in lua

Last updated: 2024-10-27

With the help of nvim-lspconfig.

Initialization

First thing you do is add the efm setup function to your Neovim configuration.

require('lspconfig').efm.setup({})

And inside the curly braces we are going to add all our options.

We need to specify the features our tools support. We do this using the init_options property.

require('lspconfig').efm.setup({
  init_options = {
    documentFormatting = false,
    documentRangeFormatting = false,
    hover = false,
    documentSymbol = false,
    completion = false,
    codeAction = false
  },
})

You might notice everything is set to false, that's because I don't know which tools you are going to use. You'll have to enable the things you want to use.

Tool config

To help you organize your code a little bit you can add the configuration for each tool inside a lua table. Here is an example.

local efm_tools = {
  some_formatter = {
    formatCommand = "example-formatter '${INPUT}'",
    formatCanRange = false,
    formatStdin = false,
  },
  some_linter = {
    lintCommand = "example-linter '${INPUT}'",
    lintStdin = false,
  },
}

Here all the configurations will be stored in the lua table efm_tools. And since lua tables can be nested we can have have each tool in its own table.

Now, how do you know which properties you can use inside each tool? formatCommand, formatStdin... where does that come from? Well, in efm's readme there is an example config written in yaml. You can see the basic configuration options they have available. And if you want to know more details go to schemas.md file.

The thing you should be aware of is in yaml you use kebab-case. But in lua you use camelCase. So, format-stdin in yaml becomes formatStdin in lua.

Language support

Now lets pretend our tools ready, how do we add them to efm?

Inside the property settings you are going to add another lua table with the languages you want to support.

local efm_tools = {
  -- code omitted for brevity....
}

require('lspconfig').efm.setup({
  init_options = {
    -- code omitted....
  },
  settings = {
    rootMarkers = {'.git/'},
    languages = {
      example_lang = {
        efm_tools.some_formatter,
        efm_tools.some_linter,
      },
    }
  },
})

Here example_lang is the language we want to support. And inside we list all the tools we want to use in this language.

What is that rootMarkers thing? That's the list of directories or files that efm will use to figure out what is the top level directory of your project. A .git directory is usually a good indicator.

The last step (optional)

The last detail you need to be aware of is the filetypes in which you want Neovim to attach the efm language server. If you don't do this, lspconfig will attach efm to every file you open.

You can ignore this step. But if you want more control over which file efm can act on, you should specify a list of valid Neovim filetypes in the filetypes property.

require('lspconfig').efm.setup({
  init_options = {
    -- code omitted....
  },
  settings = {
    -- code omitted....
  },
  filetypes = {
    'somefiletype',
    'anotherfiletype',
  },
})

Example config

This example will use prettierd and eslint_d.

Note in recent versions of eslint (v9 and greater) the visualstudio formatter was removed. You may need to install eslint-formatter-visualstudio as a dev dependency.

local efm_tools = {
  prettierd = {
    formatCommand = "prettierd '${INPUT}' ${--range-start=charStart} ${--range-end=charEnd}",
    formatStdin = true,
    formatCanRange = true,
  },
  eslint_d = {
    lintSource = 'efm/eslint_d',
    lintCommand = 'eslint_d --no-color --format visualstudio --stdin-filename "${INPUT}" --stdin',
    lintIgnoreExitCode = true,
    lintStdin = true,
    lintFormats = {
      '%f(%l,%c): %trror %m',
      '%f(%l,%c): %tarning %m'
    },
    rootMarkers = {
      'eslint.config.js',
      'eslint.config.mjs',
      'eslint.config.cjs',
      'package.json',
    },
  }
}

require('lspconfig').efm.setup({
  init_options = {
    documentFormatting = true,
    documentRangeFormatting = true,
  },
  settings = {
    rootMarkers = {'.git/'},
    languages = {
      javascript = {
        efm_tools.eslint_d,
        efm_tools.prettierd,
      },
      typescript = {
        efm_tools.eslint_d,
        efm_tools.prettierd,
      },
    },
  },
  filetypes = {
    'javascript',
    'javascriptreact',
    'javascript.jsx',
    'typescript',
    'typescriptreact',
    'typescript.jsx',
  },
})