replace vsnip with LuaSnip

* vsnip is very buggy. hrsh7th/vim-vsnip#254
* luasnip loads too many files at startup. Lazy-load it at InsertEnter
  and <C-l>.
* My patch to break undo sequence before expanding. Upstream it?
* Make vsnip snippets available for luasnip.
* Port some advanced vsnip snippets to luasnip.

configs.vim

@@ -78,8 +78,8 @@ elseif g:ide_client == 'nvim'
     Plug 'hrsh7th/cmp-nvim-lsp'
     " hrsh7th/cmp-nvim-lsp-signature-help
     Plug 'hrsh7th/cmp-path'
-    Plug 'tomtomjhj/vim-vsnip' " my fork with in-word expansion and better undo
-    Plug 'hrsh7th/cmp-vsnip'
+    Plug 'L3MON4D3/LuaSnip', { 'on': [] }
+    Plug 'saadparwaiz1/cmp_luasnip', { 'on': [] }
     Plug 'neovim/nvim-lspconfig'
     Plug 'williamboman/mason.nvim'
     Plug 'williamboman/mason-lspconfig.nvim'
@@ -483,14 +483,26 @@ if g:ide_client == 'coc'
 elseif g:ide_client == 'nvim'
     lua require'tomtomjhj/cmp'
 
-    let g:vsnip_snippet_dir = expand('~/.vim/vsnip')
-    let g:vsnip_filetypes = { 'pandoc': ['markdown', 'tex'] }
+    " lazy-load luasnip
+    let s:loaded_luasnip = get(s:, 'loaded_luasnip', 0)
+    function! s:LoadLuaSnip() abort
+        if s:loaded_luasnip | return | endif
+        call plug#load('LuaSnip', 'cmp_luasnip')
 
-    imap <expr> <C-l> vsnip#available(1) ? '<Plug>(vsnip-expand-or-jump)' : '<C-l>'
-    smap <expr> <C-l> vsnip#available(1) ? '<Plug>(vsnip-expand-or-jump)' : '<C-l>'
-    imap <expr> <C-h> vsnip#jumpable(-1) ? '<Plug>(vsnip-jump-prev)'      : '<C-h>'
-    smap <expr> <C-h> vsnip#jumpable(-1) ? '<Plug>(vsnip-jump-prev)'      : '<C-h>'
-    xmap        <C-l> <Plug>(vsnip-cut-text)
+        lua require("luasnip.loaders.from_vscode").lazy_load { paths = { "~/.vim/vsnip", "~/.vim/plugged/friendly-snippets" } }
+        lua require("luasnip.loaders.from_lua").lazy_load { paths = "~/.vim/lsnip/" }
+        lua require("luasnip").config.setup { store_selection_keys = "<C-L>" }
+
+        imap <silent><expr> <C-l> luasnip#expand_or_jumpable() ? '<Plug>luasnip-expand-or-jump' : '<C-l>'
+        inoremap <silent> <C-h> <Cmd>lua require('luasnip').jump(-1)<CR>
+        snoremap <silent> <C-l> <Cmd>lua require('luasnip').jump(1)<CR>
+        snoremap <silent> <C-h> <Cmd>lua require('luasnip').jump(-1)<CR>
+    endfunction
+
+    if has('vim_starting')
+        au InsertEnter * ++once call s:LoadLuaSnip()
+        xnoremap <silent> <C-l> :<C-u>call <SID>LoadLuaSnip()<CR>gv<Cmd>call feedkeys("<C-l>")<CR>
+    endif
 endif
 " }}}
 

lsnip/all.lua

@@ -0,0 +1,6 @@
+return {
+  s("date", p(os.date, "%Y-%m-%d")),
+  s("diso", p(os.date, "%Y-%m-%d %H:%M:%S%z")),
+  s("time", p(os.date, "%H:%M")),
+  s("modeline", fmt([[vim: set {}:]], { i(0, "opt=value") })),
+}

lua/tomtomjhj/cmp.lua

@@ -47,7 +47,7 @@ cmp.setup {
         get_bufnrs = get_visible_bufnrs,
       }
     },
-    { name = 'vsnip' },
+    { name = 'luasnip' },
     { name = 'tags' },
   },
   experimental = {
@@ -82,7 +82,7 @@ cmp.setup {
   },
   snippet = {
     expand = function(args)
-      vim.fn["vsnip#anonymous"](args.body)
+      require('luasnip').lsp_expand(args.body)
     end,
   },
   formatting = {
@@ -94,7 +94,7 @@ cmp.setup {
       vim_item.menu = ({
           buffer = "[B]",
           nvim_lsp = "[LS]",
-          vsnip = "[SN]",
+          luasnip = "[SN]",
           tags = "[T]",
         })[entry.source.name]
       return vim_item

patches/LuaSnip.patch

@@ -0,0 +1,12 @@
+diff --git a/lua/luasnip/init.lua b/lua/luasnip/init.lua
+index 99e9284..e62b88a 100644
+--- a/lua/luasnip/init.lua
++++ b/lua/luasnip/init.lua
+@@ -284,6 +284,7 @@ local function expand(opts)
+ 		local jump_into_func = opts and opts.jump_into_func
+
+ 		local cursor = util.get_cursor_0ind()
++		vim.cmd[[let &undolevels = &undolevels]]
+ 		-- override snip with expanded copy.
+ 		snip = snip_expand(snip, {
+ 			expand_params = expand_params,

vsnip/global.json

@@ -3,41 +3,5 @@
     "prefix": "lorem",
     "description": "Lorem Ipsum",
     "body": "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet."
-  },
-  "modeline": {
-    "prefix": "modeline",
-    "description": "Vim modeline",
-    "body": "vim${VIM:':set '. (&expandtab ? printf('et sw=%i ts=%i', &sw, &ts) : printf('noet sts=%i sw=%i ts=%i', &sts, &sw, &ts)) . (&tw ? ' tw='. &tw : '') . ':'}"
-  },
-  "date": {
-    "prefix": "date",
-    "description": "YYYY-MM-DD",
-    "body": "${VIM:strftime(\"%Y-%m-%d\")}"
-  },
-  "ddate": {
-    "prefix": "ddate",
-    "description": "Month DD, YYYY",
-    "body": "${VIM:strftime(\"%b %d, %Y\")}"
-  },
-  "diso": {
-    "prefix": "diso",
-    "description": "ISO format datetime",
-    "body": "${VIM:strftime(\"%Y-%m-%d %H:%M:%S%z\")}"
-  },
-  "time": {
-    "prefix": "time",
-    "description": "hh:mm",
-    "body": "${VIM:strftime(\"%H:%M\")}"
-  },
-  "datetime": {
-    "prefix": "datetime",
-    "description": "YYYY-MM-DD hh:mm",
-    "body": "${VIM:strftime(\"%Y-%m-%d %H:%M\")}"
-  },
-  "uuid": {
-    "prefix": "uuid",
-    "body": [
-      "${VIM:system('python -c \"import uuid, sys; sys.stdout.write(str(uuid.uuid4()))\"')}"
-    ]
   }
 }

vsnip/package.json

@@ -0,0 +1,39 @@
+{
+  "name": "vscode snippets for luasnip",
+  "contributes": {
+    "snippets": [
+      {
+        "language": [
+          "markdown",
+          "pandoc"
+        ],
+        "path": "./markdown.json"
+      },
+      {
+        "language": [
+          "all"
+        ],
+        "path": "./global.json"
+      },
+      {
+        "language": [
+          "coq"
+        ],
+        "path": "./coq.json"
+      },
+      {
+        "language": [
+          "rust"
+        ],
+        "path": "./rust.json"
+      },
+      {
+        "language": [
+          "tex",
+          "pandoc"
+        ],
+        "path": "./tex.json"
+      }
+    ]
+  }
+}