Use neovim's built-in lsp client

Current configuration depends on nvim-cmp and cmp-nvim-lsp for
autocompletion

nvim/init.lua

@@ -76,10 +76,81 @@ vim.cmd[[
 	\ expandtab autoindent
 ]]
 
---Color trailing spaces with red color
+--color trailing spaces with red color
 vim.cmd('highlight ExtraWhitespace ctermbg=green guibg=green')
 vim.cmd('match ExtraWhitespace /s+$/')
 vim.cmd('autocmd BufWinEnter * match ExtraWhitespace /s+$/')
 vim.cmd('autocmd InsertEnter * match ExtraWhitespace /s+%#@<!$/')
 vim.cmd('autocmd InsertLeave * match ExtraWhitespace /s+$/')
 vim.cmd('autocmd BufWinLeave * call clearmatches()')
+
+--TODO split lsp configuration into separate files
+local nvim_lsp = require('lspconfig')
+
+--add additional capabilities supported by nvim-cmp
+local capabilities = vim.lsp.protocol.make_client_capabilities()
+capabilities = require('cmp_nvim_lsp').update_capabilities(capabilities)
+
+--use an on_attach function to only map the following keys
+--after the language server attaches to the current buffer
+local on_attach = function(client, bufnr)
+  local function buf_set_keymap(...) vim.api.nvim_buf_set_keymap(bufnr, ...) end
+  local function buf_set_option(...) vim.api.nvim_buf_set_option(bufnr, ...) end
+
+  -- Enable completion triggered by <c-x><c-o>
+  buf_set_option('omnifunc', 'v:lua.vim.lsp.omnifunc')
+
+  -- Mappings.
+  local opts = { noremap=true, silent=true }
+
+  --see `:help vim.lsp.*` for documentation on any of the below functions
+  buf_set_keymap('n', 'gD', '<cmd>lua vim.lsp.buf.declaration()<CR>', opts)
+  buf_set_keymap('n', 'gd', '<cmd>lua vim.lsp.buf.definition()<CR>', opts)
+  buf_set_keymap('n', 'K', '<cmd>lua vim.lsp.buf.hover()<CR>', opts)
+  buf_set_keymap('n', 'gi', '<cmd>lua vim.lsp.buf.implementation()<CR>', opts)
+  buf_set_keymap('n', '<C-k>', '<cmd>lua vim.lsp.buf.signature_help()<CR>', opts)
+end
+
+--enable some language servers with the additional completion capabilities
+--offered by nvim-cmp
+local servers = { 'pyright', }
+for _, lsp in ipairs(servers) do
+  nvim_lsp[lsp].setup {
+    on_attach = on_attach,
+    capabilities = capabilities,
+  }
+end
+
+--nvim-cmp setup
+local cmp = require('cmp')
+cmp.setup {
+  mapping = {
+    ['<C-p>'] = cmp.mapping.select_prev_item(),
+    ['<C-n>'] = cmp.mapping.select_next_item(),
+    ['<C-d>'] = cmp.mapping.scroll_docs(-4),
+    ['<C-f>'] = cmp.mapping.scroll_docs(4),
+    ['<C-Space>'] = cmp.mapping.complete(),
+    ['<C-e>'] = cmp.mapping.close(),
+    ['<CR>'] = cmp.mapping.confirm {
+      behavior = cmp.ConfirmBehavior.Replace,
+      select = true,
+    },
+    ['<Tab>'] = function(fallback)
+      if cmp.visible() then
+        cmp.select_next_item()
+      else
+        fallback()
+      end
+    end,
+    ['<S-Tab>'] = function(fallback)
+      if cmp.visible() then
+        cmp.select_prev_item()
+      else
+        fallback()
+      end
+    end,
+  },
+  sources = {
+    { name = 'nvim_lsp' },
+  },
+}