nvim/plug: +nvim-cmp@master +cmp plugins...

This commit adds (nvim-)cmp as our completion engine / framework.

We also add completion sources for (file)paths, buffer contents, LSP
actions and snippets -- courtesy of vsnip.

This provides similar functionality to coc's completion engine, but
with (much) better support for LSP actions, lua native key maps and
significantly more configuration options that can be easily overridden
but psoxizsh users.

We add similar default key maps as with what existed in coc, namely
that <CR> exits the autocompletion window, <C-Space> does the selected
LSP action, <Tab>/<S-Tab> cycles through options and <PageUp/Down>
scrolls documentation of the current item.

We also explicitly enable completion / snippet support in client capacities
sent to LSP servers, as many require this before offering completions

nvim/lua/psoxizsh/key/map.lua

@@ -64,6 +64,21 @@ M.Global.C {
 -- ############################
 M.Global.I {
   { mode = 'i' },
+
+  -- #####################
+  -- ## Auto completion ##
+  -- #####################
+  --
+  Completion = G {
+    { skip = true },
+
+    Confirm    = B { 'Select the active completion entry and insert it'          , key = '<C-Space>'  , } ,
+    Next       = B { 'Cycle selected completion item in completion menu'         , key = '<Tab>'      , } ,
+    Prev       = B { 'Reverse cycle selected completion item in completion menu' , key = '<S-Tab>'    , } ,
+    ScrollUp   = B { 'Scroll up completion item documentation'                   , key = '<PageUp>'   , } ,
+    ScrollDown = B { 'Scroll down completion item documentation'                 , key = '<PageDown>' , } ,
+
+  },
 }
 
 -- ############################
@@ -71,6 +86,8 @@ M.Global.I {
 -- ############################
 M.Global.V {
   { mode = 'v' },
+
+  Completion = M.Global.I.Completion:new({ mode = 'v' })
 }
 
 M.Buffer.N {

nvim/lua/psoxizsh/plugins/config/lspconfig.lua

@@ -1,5 +1,5 @@
 return function()
-  local lspconfig, util = require 'lspconfig', require 'psoxizsh.util'
+  local lspconfig, cmp, util = require 'lspconfig', require 'cmp_nvim_lsp', require 'psoxizsh.util'
   local keys, servers = require 'psoxizsh.key', require 'psoxizsh.lsp.servers'
 
   local defaults = {}
@@ -9,6 +9,11 @@ return function()
     keys.Buffer.Lsp:register({ buffer = bnum })
   end
 
+  -- Update LSP capabilities we send to servers to include the features supported by nvim-cmp
+  defaults.capabilities = cmp.update_capabilities(lspconfig.util.default_config.capabilities)
+  -- Dependent on a snippet manager in nvim-cmp (currently using vsnip)
+  defaults.capabilities.textDocument.completion.completionItem.snippetSupport = true
+
   -- Ideally, this would be registered on some Psoxizsh.Plug.Post autocmd
   -- but I don't feel like refactoring psoxizsh.plugin now.
   --

nvim/lua/psoxizsh/plugins/config/nvim-cmp.lua

@@ -0,0 +1,93 @@
+return function()
+  local cmp, util = require 'cmp', require 'psoxizsh.util'
+  local kmap, cfg, lspkind = cmp.mapping, cmp.config, require 'lspkind'
+  local sources, w = cfg.sources, cfg.window
+  local mode = { insert = kmap.preset.insert, cmd = kmap.preset.cmdline }
+
+  local defaults = { snippet = {}, mapping = {}, sources = {} }
+
+  local has_words_before = function()
+    local line, col = unpack(vim.api.nvim_win_get_cursor(0))
+    return col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match('%s') == nil
+  end
+
+  local fkey = function(key, md)
+    vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes(key, true, true, true), md or '', true)
+  end
+
+  -- Snippet provider
+  defaults.snippet.expand = function(args)
+    vim.fn['vsnip#anonymous'](args.body)
+  end
+
+  -- Key maps for auto completion
+  defaults.mapping = {
+      ['<Tab>'] = kmap(function(fallback)
+        if cmp.visible() then
+          cmp.select_next_item()
+        elseif vim.fn['vsnip#available'](1) == 1 then
+          fkey '<Plug>(vsnip-expand-or-jump)'
+        elseif has_words_before() then
+          cmp.complete()
+        else
+          fallback()
+        end
+      end, { 'i', 's' }),
+      ['<S-Tab>'] = kmap(function()
+        if cmp.visible() then
+          cmp.select_prev_item()
+        elseif vim.fn['vsnip#jumpable'](-1) == 1 then
+          fkey '<Plug>(vsnip-jump-prev)'
+        end
+      end, { 'i', 's' }),
+      ['<PageUp>']    = kmap.scroll_docs(-4),
+      ['<PageDown>']  = kmap.scroll_docs(4),
+      ['<C-Space>']   = kmap.confirm({ behavior = cmp.ConfirmBehavior.Insert, select = true }),
+  }
+  defaults.mapping = mode.insert(defaults.mapping)
+  defaults.mapping = mode.cmd(defaults.mapping)
+
+  -- Sources of auto completion
+  --
+  -- Each group of completions is prioritized in ascending order;
+  -- that is, 'path's will be shown before 'nvim_lsp's, etc
+  defaults.sources = sources(
+    {
+      { name = 'path',                                            },
+    },
+    {
+      { name = 'nvim_lsp',                    keyword_length = 2  },
+      { name = 'nvim_lsp_signature_help',                         },
+    },
+    {
+      { name = 'vsnip',                       keyword_length = 2  },
+    },
+    {
+      { name = 'buffer',                      keyword_length = 2  },
+    }
+  )
+
+  -- Auto completion window settings
+  defaults.window = {
+    completion = {
+      col_offset = -3,
+      side_padding = 0,
+    },
+    documentation = w.bordered(),
+  }
+
+  -- Auto completion item formatting
+  defaults.formatting = {
+    fields = { 'kind', 'abbr', 'menu' },
+    format = function(entry, item)
+      local kind = lspkind.cmp_format({ mode = 'symbol_text', maxwidth = 50 })(entry, item)
+      local strings = vim.split(kind.kind, '%s', { trimempty = true })
+      kind.kind = ' ' .. strings[1] .. ' '
+      kind.menu = '    (' .. strings[2] .. ')'
+
+      return kind
+    end,
+  }
+
+  cmp.setup(util.mconfig('config.nvim-cmp', defaults))
+end

nvim/lua/psoxizsh/plugins/plug.lua

@@ -120,12 +120,32 @@ local plugins = {
   { 'luochen1990/rainbow' },
   { 'sheerun/vim-polyglot' },
 
+  -- Autocompletion + snippets + vim.diagnostic sources
+  -- Completion framework
+  { 'hrsh7th/nvim-cmp',
+      requires = { 'onsails/lspkind.nvim' },
+      config = require 'psoxizsh.plugins.config.nvim-cmp'
+  },
+
+  -- Snippets
+  { 'hrsh7th/vim-vsnip' },
+
+  -- LSP sources
+  { 'hrsh7th/cmp-nvim-lsp' },
+  { 'hrsh7th/cmp-nvim-lsp-signature-help' },
+
+  -- Other sources:
+  { 'hrsh7th/cmp-vsnip' },
+  { 'hrsh7th/cmp-path' },
+  { 'hrsh7th/cmp-buffer' },
+
   -- Tree sitter
   { 'nvim-treesitter/nvim-treesitter',
       requires = { 'p00f/nvim-ts-rainbow' },
       run = function() require('nvim-treesitter.install').update({ with_sync = true }) end,
       config = require 'psoxizsh.plugins.config.nvim-treesitter'
   },
+
   -- Fuzzy search helpers
   { 'junegunn/fzf',
       cmd = 'FZF',