Iron out bugs and document completions plugin setup

lua/plugins/completions.lua

@@ -1,44 +1,62 @@
 return {
   'neovim/nvim-lspconfig',
+
   dependencies = {
+    -- Language server management plugins
     'williamboman/mason.nvim',
     'williamboman/mason-lspconfig.nvim',
 
-    'hrsh7th/cmp-nvim-lsp',
-    'hrsh7th/cmp-buffer',
-    'hrsh7th/cmp-path',
-    'hrsh7th/cmp-cmdline',
-    'hrsh7th/nvim-cmp',
+    -- Completion plugins
+    'hrsh7th/cmp-nvim-lsp', -- Source for built-in language server client
+    'hrsh7th/cmp-buffer',   -- Source for buffer words
+    'hrsh7th/cmp-path',     -- Source for filesystem paths
+    'hrsh7th/cmp-cmdline',  -- Source for command-line
+    'hrsh7th/nvim-cmp',     -- Completion engine combines and use the above
 
+    -- Lue vim module support in lua language server
     'folke/neodev.nvim',
 
+    -- Snippet pluggins
+    'L3MON4D3/LuaSnip',
+    'saadparwaiz1/cmp_luasnip',
+
     -- TODO: https://github.com/j-hui/fidget.nvim
+
     -- TODO: https://github.com/nvimtools/none-ls.nvim
+
     -- TODO: https://github.com/mfussenegger/nvim-dap
     -- TODO: https://github.com/rcarriga/nvim-dap-ui
   },
-  config = function()
-    require('neodev').setup()
 
+  config = function()
     require('mason').setup()
     require('mason-lspconfig').setup({
       ensure_installed = {
         'clangd',
         'cmake',
+        'jsonls',
         'lua_ls',
+        'lemminx',
+        'vimls',
+        'yamlls',
       },
       automatic_installation = false,
       handlers = {
+        -- Default handler, sets up everything unless a custom language server
+        -- setup handler is defined below
         function(server_name)
           require('lspconfig')[server_name].setup({})
         end,
+
         ['lua_ls'] = function()
+          require('neodev').setup()
           local lspconfig = require('lspconfig')
           lspconfig.lua_ls.setup({
             settings = {
               Lua = {
                 diagnostics = {
-                  disable = { "missing-fields" },
+                  disable = { 'missing-fields', },
+                  globals = { 'vim', },
                 }
               }
             }
@@ -47,17 +65,29 @@ return {
       },
     })
 
-    require('cmp').setup({
+    local cmp = require('cmp')
+    cmp.setup({
+      snippet = {
+        expand = function(args)
+          require('luasnip').lsp_expand(args.body)
+        end
+      },
+      mapping = cmp.mapping.preset.insert({
+        ['<C-p>'] = cmp.mapping.select_prev_item(),
+        ['<C-n>'] = cmp.mapping.select_next_item(),
+        ['<C-y>'] = cmp.mapping.confirm({ select = true }),
+      }),
       sources = {
         { name = 'nvim_lsp' },
-        -- TODO: snippets
+        { name = 'luasnip' },
+        { name = 'buffer' },
+        { name = 'path' },
+        { name = 'cmdline' },
       },
     })
 
     -- Disable displaying diagnostics as virtual text
-    vim.diagnostic.config({
-      virtual_text = false,
-    })
+    vim.diagnostic.config({ virtual_text = false })
 
     -- Diagnostic mappings
     -- TODO: trouble.nvim mappings instead? https://youtu.be/MuUrCcvE-Yw?t=631
@@ -73,27 +103,26 @@ return {
       callback = function(ev)
         local opts = { noremap = true, buffer = ev.buf }
 
-        -- FIXME: Should I drop this? It's only for expanding snippets because
+        -- TODO: Should I drop this? It's only for expanding snippets because
         -- coc.nvim was being weird about it
         -- inoremap <silent><expr> <TAB> coc#pum#visible() ? coc#pum#confirm() : "\<TAB>"
 
-        vim.keymap.set('n', '<leader>fi', function()
-          -- FIXME: This doesn't stop the prompt to select the code action when
-          -- there is only one. Also not sure if its actually filtering
-          vim.lsp.buf.code_action({ context = { only = { 'quickfix' } } })
-        end, opts)
+        -- Fixit mapping, or close enough, actually any code action
+        vim.keymap.set('n', '<leader>fi', vim.lsp.buf.code_action, opts)
 
+        -- Goto definition mapping
         vim.keymap.set('n', 'gd', vim.lsp.buf.definition, opts)
-
-        -- nnoremap <silent> <leader>gt <Plug>(coc-type-definition)
-
-        vim.keymap.set('n', '<leader>gr', vim.lsp.buf.references, opts)
-
+        -- TODO: nnoremap <silent> <leader>gt <Plug>(coc-type-definition)
         -- nnoremap <silent> <leader>gu <Plug>(coc-references-used)
 
+        -- Get references to symbol under cursor, store in quickfix window
+        vim.keymap.set('n', '<leader>gr', vim.lsp.buf.references, opts)
+
         -- Refactoring mappings
         vim.keymap.set('n', '<leader>rn', vim.lsp.buf.rename, opts)
-        -- TODO: vim.lsp.buf.format
+
+        -- Format whole buffer mapping
+        vim.keymap.set('n', '<leader>gq', vim.lsp.buf.format, opts)
 
         -- Help mappings
         vim.keymap.set('n', 'K', vim.lsp.buf.hover, opts)