dotfiles/nvim/.config/nvim/lua/lsp.lua

local nvim_lsp   = require('lspconfig')
local protocol   = require('vim.lsp.protocol')
local signature  = require('lsp_signature')

-- Taken from https://www.reddit.com/r/neovim/comments/gyb077/nvimlsp_peek_defination_javascript_ttserver/
function preview_location(location, context, before_context)
  -- location may be LocationLink or Location (more useful for the former)
  context = context or 10
  before_context = before_context or 5
  local uri = location.targetUri or location.uri
  if uri == nil then
    return
  end
  local bufnr = vim.uri_to_bufnr(uri)
  if not vim.api.nvim_buf_is_loaded(bufnr) then
    vim.fn.bufload(bufnr)
  end
  local range = location.targetRange or location.range
  local contents =
    vim.api.nvim_buf_get_lines(bufnr, range.start.line - before_context, range["end"].line + 1 + context, false)
  local filetype = vim.api.nvim_buf_get_option(bufnr, "filetype")
  return vim.lsp.util.open_floating_preview(contents, filetype)
end

function preview_location_callback(_, method, result)
  local context = 10
  if result == nil or vim.tbl_isempty(result) then
    print("No location found: " .. method)
    return nil
  end
  if vim.tbl_islist(result) then
    floating_buf, floating_win = preview_location(result[1], context)
  else
    floating_buf, floating_win = preview_location(result, context)
  end
end

function peek_definition()
  if vim.tbl_contains(vim.api.nvim_list_wins(), floating_win) then
    vim.api.nvim_set_current_win(floating_win)
  else
    local params = vim.lsp.util.make_position_params()
    return vim.lsp.buf_request(0, "textDocument/definition", params, preview_location_callback)
  end
end

local on_attach = function(client, bufnr)
  signature.on_attach({
    bind         = true,
    hint_enable  = true,
    hint_prefix  = "🐼 ",
    hint_scheme  = "String",
    handler_opts = { border = "single" },
    decorator    = {"`", "`"}
  })
  vim.api.nvim_buf_set_option(bufnr, 'omnifunc', 'v:lua.vim.lsp.omnifunc')

  if client.config.flags then
    client.config.flags.allow_incremental_sync = true
    client.config.flags.debounce_text_changes  = 100
  end

  local opts = { noremap=true, silent=true }

  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'K',  '<cmd>lua vim.lsp.buf.hover()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gr', '<cmd>lua vim.lsp.buf.references()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'ga', '<cmd>lua vim.lsp.buf.code_action()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '<C-k>', '<cmd>lua vim.lsp.buf.type_definition()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '1gd', '<cmd>lua vim.lsp.buf.document_symbol()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '1gD', '<cmd>lua vim.lsp.buf.workspace_symbol()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gR', '<cmd>lua vim.lsp.buf.rename()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'pd', '<cmd>lua peek_definition()<CR>', opts)

  vim.api.nvim_buf_set_keymap(bufnr, 'n', '[d', '<cmd>lua vim.lsp.diagnostic.goto_prev { wrap = false }<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', ']d', '<cmd>lua vim.lsp.diagnostic.goto_next { wrap = false }<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', '[D', '<cmd>lua vim.lsp.diagnostic.goto_prev()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', ']D', '<cmd>lua vim.lsp.diagnostic.goto_next()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', 'do', '<cmd>lua vim.lsp.diagnostic.set_loclist()<CR>', opts)
  vim.api.nvim_buf_set_keymap(bufnr, 'n', ',d', '<cmd>lua vim.lsp.diagnostic.show_line_diagnostics()<CR>', opts)

  if client.resolved_capabilities.document_formatting then
    vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gq', '<cmd>lua vim.lsp.buf.formatting()<CR>', opts)
  elseif client.resolved_capabilities.document_range_formatting then
    vim.api.nvim_buf_set_keymap(bufnr, 'n', 'gq', '<cmd>lua vim.lsp.buf.formatting()<CR>', opts)
  end

  protocol.CompletionItemKind = {
    ' '; -- text
    ' '; -- method
    ' '; -- function
    '全'; -- ctor
    ' '; -- field
    ' '; -- variable
    ' '; -- class
    ' '; -- interface
    ' '; -- module
    ' '; -- property
    ' '; -- unit
    ' '; -- value
    '螺'; -- enum
    ' '; -- keyword
    ' '; -- snippet
    ' '; -- color
    ' '; -- file
    ' '; -- reference
    ' '; -- folder
    ' '; -- enum member
    ' '; -- constant
    ' '; -- struct
    ' '; -- event
    '璉'; -- operator
    ' '; -- type parameter
  }
end

local servers = { 'hls', 'rust_analyzer', 'pyls', 'tsserver' }
for _, lsp in ipairs(servers) do
  nvim_lsp[lsp].setup {
    on_attach = on_attach,
  }
end