[nvim] Fix nvim-cmp keybindings and update misc nvim-cmp configuration.

.config/nvim/init.vim

@@ -8,6 +8,7 @@ lua << EOF
 vim.opt.completeopt = {"menu", "menuone", "noselect"}
 
 local cmp = require'cmp'
+local source_mapping = {buffer = '[Buffer]', nvim_lsp = '[LSP]'}
 
 cmp.setup({
     snippet = {
@@ -15,24 +16,26 @@ cmp.setup({
             require('luasnip').lsp_expand(args.body) -- For `luasnip` users.
         end,
     },
-    mapping = {
+    mapping = cmp.mapping.preset.insert({
-        -- ['<C-b>'] = cmp.mapping(cmp.mapping.scroll_docs(-4), { 'i', 'c' }),
+        ['<C-f>'] = cmp.mapping(cmp.mapping.scroll_docs( 4), { 'i', 'c' }),
-        -- ['<C-f>'] = cmp.mapping(cmp.mapping.scroll_docs(4), { 'i', 'c' }),
+        ['<C-b>'] = cmp.mapping(cmp.mapping.scroll_docs(-4), { 'i', 'c' }),
         ['<C-Space>'] = cmp.mapping(cmp.mapping.complete(), { 'i', 'c' }),
-        -- ['<C-y>'] = cmp.config.enable, -- Specify `cmp.config.disable` if you want to remove the default `<C-y>` mapping.
+        ['<CR>'] = cmp.mapping.confirm({ select = false }),
-        -- ['<C-e>'] = cmp.mapping({
+    }),
-        --     i = cmp.mapping.abort(),
-        --   c = cmp.mapping.close(),
-        -- }),
-        ['<CR>'] = cmp.mapping.confirm({ select = true }), -- Accept currently selected item. Set `select` to `false` to only confirm explicitly selected items.
-    },
     sources = cmp.config.sources({
         { name = 'nvim_lsp' },
-        { name = 'luasnip' }, -- For luasnip users.
+        { name = 'luasnip' },
     },
     {
         { name = 'buffer' },
-    })
+    }),
+    completion = {keyword_length = 4},
+    formatting = {
+        format = function(entry, vim_item)
+            vim_item.menu = source_mapping[entry.source.name]
+            return vim_item
+        end,
+    },
 })
 
 -- Setup lspconfig: capabilities is passed to lspconfig.$server.setup