first version

lua/luadev.lua

@@ -0,0 +1,69 @@
+local a = vim.api
+if __lua_dev_state == nil then
+    __lua_dev_state = {}
+end
+local s = __lua_dev_state
+
+local function create_buf(window)
+  if s.buf ~= nil then
+    return
+  end
+  local w0 = a.nvim_get_current_win()
+  a.nvim_command("new")
+  local buf = a.nvim_get_current_buf()
+  a.nvim_buf_set_option(buf, 'swapfile', false)
+  a.nvim_buf_set_option(buf, 'buftype', 'nofile')
+  a.nvim_buf_set_name(buf, "[nvim-lua]")
+
+  if not window then
+    a.nvim_command("quit")
+  end
+  a.nvim_set_current_win(w0)
+  s.buf = buf
+end
+
+local function append_buf(lines, hl)
+  local l0 = a.nvim_buf_line_count(s.buf)
+  if type(lines) == type("") then
+    unimplemented()
+  end
+  a.nvim_buf_set_lines(s.buf, l0, l0, true, lines)
+  if hl ~= nil then
+    for i = l0, a.nvim_buf_line_count(s.buf)-1 do
+      a.nvim_buf_add_highlight(s.buf, -1, hl, i, 0, -1)
+    end
+  end
+  -- TODO: scroll!
+  return l0
+end
+
+local function luadev_print(x) -- TODO: ...
+  local str = tostring(x)
+  append_buf({str})
+end
+
+local function exec(str)
+  local s, err = loadstring(str,"g")
+  if s == nil then
+    append_buf({err},"WarningMsg")
+  else
+    local oldprint = _G.print
+    _G.print = luadev_print
+    s, err = pcall(s)
+    _G.print = oldprint
+    if s == false then
+      append_buf({err},"WarningMsg")
+    end
+  end
+end
+
+local function start()
+  create_buf(true)
+end
+
+return {
+  start=start,
+  exec=exec,
+  print=luadev_print,
+  append_buf=append_buf
+}

plugin/luadev.vim

@@ -0,0 +1,3 @@
+command! Luadev lua require'luadev'.start()
+
+nnoremap <Plug>(Luadev-Run) <Cmd>lua require'luadev'.exec(vim.api.nvim_get_current_line())<cr>