nvim-config/lua/plugins/language-manager.lua

--[[
local lm = require('language_manager')
lm.install() or .install({'ts_parsers','language_servers','linters','formatters'})
  - treesitter.install specs.ts_parsers
  - mason.install mason-registry.get_package(name):install()
lm.generate_specs() or {use_cache=true, only_installed=true}
lm.delete_cache()
lm.enable()
--]]


vim.pack.add({ 'https://github.com/mason-org/mason.nvim' })

local M = {}
M.lsp = {}
M.ts = {}
M.lint = {}
M.format = {}

M.group = vim.api.nvim_create_augroup('language-manager', { clear = true })

local function wrap(item)
  if type(item) == 'string' then
    return { item }
  elseif type(item) == 'table' then
    return item
  else
    return {}
  end
end

local function create_set()
  local seen = {}
  return function(ref, item) -- unique()
    if not seen[ref] then
      seen[ref] = {}
    end
    if item and not seen[ref][item] then
      seen[ref][item] = true
      return true
    end
    return false
  end
end

local function create_spec()
  local S = {}
  local unique = create_set()
  local specs = {}

  function S.set(item, group)
    specs[group] = item
  end

  function S.get()
    return specs
  end

  function S.add(list, ...)
    local groups = { ... }
    local ref = table.concat(groups, '.')
    local pointer = specs
    local last_i = #groups

    for i = 1, last_i do
      local group = groups[i]

      if i == last_i then
        for _, item in ipairs(wrap(list)) do
          if unique(ref, item) then
            if not pointer[group] then
              pointer[group] = {}
            end
            table.insert(pointer[group], item)
          end
        end
      else
        if not pointer[group] then
          pointer[group] = {}
        end
        pointer = pointer[group]
      end
    end
  end

  return S
end

function M.generate_specs(specs_raw)
  local specs = create_spec()

  for _, spec in ipairs(specs_raw) do
    -- <filetype> -> { ft = <filetype> }
    if type(spec) == 'string' then
      spec = { ft = spec }
    end

    -- Filetype = TS Parser
    if not spec.ts then
      spec.ts = spec.ft
    end

    specs.add(spec.ts, 'ts_parsers')
    specs.add(spec.lsp, 'language_servers')

    for _, filetype in ipairs(wrap(spec.ft)) do
      specs.add(spec.lint, 'linters_by_ft', filetype)
      specs.add(spec.format, 'formatters_by_ft', filetype)
    end
  end

  M.general = specs.get()
  return M.general
end

function M.lsp.setup()
  require('mason').setup()
  local registry = require('mason-registry')

  for _, lsp in ipairs(M.general.language_servers) do
    if registry.has_package(lsp) then
      local pkg = registry.get_package(lsp)
      local spec = pkg.spec and pkg.spec.neovim
      local lsp_name = (spec and spec.lspconfig) or lsp

      vim.lsp.enable(lsp_name)
    else
      vim.notify('Unknown LSP: ' .. lsp, vim.log.levels.WARN)
    end
  end
end

function M.ts.setup()
  require('nvim-treesitter.configs').setup({
    highlight = { enable = true },
    incremental_selection = { enable = true },
  })
end

function M.lint.setup()
  vim.api.nvim_create_autocmd({ 'BufReadPre', 'BufNewFile' }, {
    group = M.group,
    callback = function()
      local lint = require('lint')
      lint.linters_by_ft = M.general.linters_by_ft
      vim.api.nvim_create_autocmd({ 'BufEnter', 'BufWritePost', 'InsertLeave' }, {
        group = vim.api.nvim_create_augroup('language-manager.lint', { clear = true }),
        callback = function()
          lint.try_lint()
        end,
      })
    end,
  })
end

function M.format.setup()
  vim.api.nvim_create_autocmd('BufWritePre', {
    group = M.group,
    once = true,
    callback = function()
      require('conform').setup({
        format_on_save = { timeout_ms = 500, lsp_format = 'fallback' },
        default_format_opts = { stop_after_first = true },
        formatters_by_ft = M.general.formatters_by_ft,
      })
    end,
  })
end

return M