feat(tagbar): use default logger system

.gitignore

@@ -1,4 +1,5 @@
 !0/
+.spacevim.log
 doc/tags
 doc/tags-cn
 .ropeproject/

autoload/SpaceVim/logger.vim

@@ -7,6 +7,8 @@
 "=============================================================================
 
 if has('nvim-0.5.0')
+  ""
+  " write message to SpaceVim runtime log with `info` level.
   function! SpaceVim#logger#info(msg) abort
     lua require("spacevim.logger").info(
           \ require("spacevim").eval("a:msg")
@@ -55,7 +57,26 @@ if has('nvim-0.5.0')
   function! SpaceVim#logger#setOutput(file) abort
     lua require("spacevim.logger").setOutput(require("spacevim").eval("a:file"))
   endfunction
-
+  ""
+  " Derive a new logger based on SpaceVim's runtime logger. The new logger
+  " provides following functions:
+  " 1. info(msg): like |SpaceVim#logger#info|, but include the derive name.
+  " 2. warn(msg): like |SpaceVim#logger#warn|
+  " 3. error(msg): like |SpaceVim#logger#error|
+  " 4. debug(msg): write debug message run SpaceVim runtime log
+  " 5. start_debug(): enable debug mode of derived logger.
+  " 6. stop_debug(): stop debug mode of derived logger.
+  "
+  " Example: >
+  "   let s:LOGGER = SpaceVim#logger#derive('myplug')
+  "
+  "   call s:LOGGER.info('hello world')
+  " <
+  "
+  " The this info message will be write to SpaceVim's runtime log:
+  " >
+  "   [  myplug ] [00:02:54:051] [ Info  ] hello world
+  " <
   function! SpaceVim#logger#derive(name) abort
     return luaeval('require("spacevim.logger").derive(require("spacevim").eval("a:name"))')
   endfunction
@@ -176,6 +197,8 @@ else
 
   let s:derive = {}
   let s:derive.origin_name = s:LOGGER.get_name()
+  " let s:derive._debug_mode = v:false
+  let s:derive._debug_mode = 0
 
   function! s:derive.info(msg) abort
     call s:LOGGER.set_name(self.derive_name)
@@ -196,9 +219,19 @@ else
   endfunction
 
   function! s:derive.debug(msg) abort
-    call s:LOGGER.set_name(self.derive_name)
+    if self._debug_mode
-    call s:LOGGER.debug(a:msg)
+      call s:LOGGER.set_name(self.derive_name)
-    call s:LOGGER.set_name(self.origin_name)
+      call s:LOGGER.debug(a:msg)
+      call s:LOGGER.set_name(self.origin_name)
+    endif
+  endfunction
+
+  function! s:derive.start_debug() abort
+    let self._debug_mode = 1
+  endfunction
+
+  function! s:derive.stop_debug() abort
+    let self._debug_mode = 0
   endfunction
 
   function! SpaceVim#logger#derive(name) abort

bundle/tagbar/autoload/tagbar/debug.vim

@@ -1,62 +0,0 @@
-function! tagbar#debug#start_debug(...) abort
-    let filename = a:0 > 0 ? a:1 : ''
-
-    if empty(filename)
-        let s:debug_file = 'tagbardebug.log'
-    else
-        let s:debug_file = filename
-    endif
-
-    " Clear log file and start it with version info
-    exe 'redir! > ' . s:debug_file
-    silent version
-    redir END
-
-    " Check whether the log file could be created
-    if !filewritable(s:debug_file)
-        echomsg 'Tagbar: Unable to create log file ' . s:debug_file
-        let s:debug_file = ''
-        return
-    endif
-
-    let s:debug_enabled = 1
-endfunction
-
-function! tagbar#debug#stop_debug() abort
-    let s:debug_enabled = 0
-    let s:debug_file = ''
-endfunction
-
-function! tagbar#debug#log(msg) abort
-    if s:debug_enabled
-        execute 'redir >> ' . s:debug_file
-        silent echon s:gettime() . ': ' . a:msg . "\n"
-        redir END
-    endif
-endfunction
-
-function! tagbar#debug#log_ctags_output(output) abort
-    if s:debug_enabled
-        exe 'redir! > ' . s:debug_file . '.ctags_out'
-        silent echon a:output
-        redir END
-    endif
-endfunction
-
-function! tagbar#debug#enabled() abort
-    return s:debug_enabled
-endfunction
-
-if has('reltime')
-    function! s:gettime() abort
-        let time = split(reltimestr(reltime()), '\.')
-        return strftime('%Y-%m-%d %H:%M:%S.', time[0]) . time[1]
-    endfunction
-else
-    function! s:gettime() abort
-        return strftime('%Y-%m-%d %H:%M:%S')
-    endfunction
-endif
-
-let s:debug_enabled = 0
-let s:debug_file = ''

bundle/tagbar/autoload/tagbar/log.vim

@@ -0,0 +1,35 @@
+"=============================================================================
+" log.vim --- logger for tagbar
+" Copyright (c) 2016-2019 Wang Shidong & Contributors
+" Author: Wang Shidong < wsdjeg@outlook.com >
+" URL: https://spacevim.org
+" License: GPLv3
+"=============================================================================
+
+if exists('s:debug_enabled')
+  finish
+endif
+
+let s:LOGGER =SpaceVim#logger#derive('tagbar')
+
+function! tagbar#log#start_debug(...) abort
+  call s:LOGGER.info('enable debug mode!')
+  call s:LOGGER.start_debug()
+endfunction
+
+function! tagbar#log#stop_debug() abort
+  call s:LOGGER.info('disable debug mode!')
+  call s:LOGGER.stop_debug()
+endfunction
+
+function! tagbar#log#debug(msg) abort
+  call s:LOGGER.debug(a:msg)
+endfunction
+
+function! tagbar#log#info(msg) abort
+  call s:LOGGER.info(a:msg)
+endfunction
+
+function! tagbar#log#enabled() abort
+  return s:LOGGER.enabled()
+endfunction

bundle/tagbar/doc/tagbar.txt

@@ -307,15 +307,13 @@ COMMANDS                                                     *tagbar-commands*
     makes sense to customize. See |tagbar-extend| for more information about
     type configurations.
 
-:TagbarDebug [logfile]                                          *:TagbarDebug*
+:TagbarDebug                                                  *:TagbarDebug*
-    Start debug mode. This will write debug messages to file [logfile] while
+    Start debug mode. This will put debug message to SpaceVim runtime log.
-    using Tagbar. If no argument is given "tagbardebug.log" in the current
+    which can be found via `SPC h L`
-    directory is used. Note: an existing file will be overwritten!
-    Note also that it is usually necessary to call this command before loading
-    a file that creates problems in order to get all of the needed data.
 
 :TagbarDebugEnd                                              *:TagbarDebugEnd*
-    End debug mode, debug messages will no longer be written to the logfile.
+    End debug mode, debug messages will no longer be written SpaceVim runtime
+    log.
 
 :TagbarForceUpdate                                        *:TagbarForceUpdate*
     Forcefully update a file even if it exceeds the |g:tagbar_file_size_limit|

bundle/tagbar/plugin/tagbar.vim

@@ -193,8 +193,8 @@ command! -nargs=1 -bang TagbarSetFoldlevel  call tagbar#SetFoldLevel(<args>, <ba
 command! -nargs=0 TagbarShowTag       call tagbar#highlighttag(1, 1)
 command! -nargs=* TagbarCurrentTag    echo tagbar#currenttag('%s', 'No current tag', <f-args>)
 command! -nargs=1 TagbarGetTypeConfig call tagbar#gettypeconfig(<f-args>)
-command! -nargs=? TagbarDebug         call tagbar#debug#start_debug(<f-args>)
+command! -nargs=0 TagbarDebug         call tagbar#log#start_debug()
-command! -nargs=0 TagbarDebugEnd      call tagbar#debug#stop_debug()
+command! -nargs=0 TagbarDebugEnd      call tagbar#log#stop_debug()
 command! -nargs=0 TagbarTogglePause   call tagbar#toggle_pause()
 command! -nargs=0 TagbarForceUpdate   call tagbar#ForceUpdate()
 command! -nargs=0 TagbarJump   call tagbar#jump()

doc/SpaceVim.txt

@@ -1645,6 +1645,31 @@ SpaceVim#layers#load({layer})                         *SpaceVim#layers#load()*
       \ )
 <
 
+SpaceVim#logger#info({msg})                           *SpaceVim#logger#info()*
+  write message to SpaceVim runtime log with `info` level.
+
+SpaceVim#logger#derive({name})                      *SpaceVim#logger#derive()*
+  Derive a new logger based on SpaceVim's runtime logger. The new logger
+  provides following functions:
+    1. info(msg): like |SpaceVim#logger#info|, but include the derive name.
+    2. warn(msg): like |SpaceVim#logger#warn|
+    3. error(msg): like |SpaceVim#logger#error|
+    4. debug(msg): write debug message run SpaceVim runtime log
+    5. start_debug(): enable debug mode of derived logger.
+    6. stop_debug(): stop debug mode of derived logger.
+
+  Example:
+>
+    let s:LOGGER = SpaceVim#logger#derive('myplug')
+
+    call s:LOGGER.info('hello world')
+<
+
+  The this info message will be write to SpaceVim's runtime log:
+>
+    [  myplug ] [00:02:54:051] [ Info  ] hello world
+<
+
 SpaceVim#logger#setLevel({level})                 *SpaceVim#logger#setLevel()*
   Set debug level of SpaceVim. Default is 1.
 

lua/spacevim/api/logger.lua

@@ -11,155 +11,165 @@ local fn = vim.fn or require('spacevim').fn
 local cmd = require('spacevim').cmd
 
 local M = {
-    ['name'] = '',
+  ['name'] = '',
-    ['silent'] = 1,
+  ['silent'] = 1,
-    ['level'] = 1,
+  ['level'] = 1,
-    ['verbose'] = 1,
+  ['verbose'] = 1,
-    ['file'] = '',
+  ['file'] = '',
-    ['temp'] = {},
+  ['temp'] = {},
 }
 
-
 -- 0 : log debug, info, warn, error messages
 -- 1 : log info, warn, error messages
 -- 2 : log warn, error messages
 -- 3 : log error messages
-M.levels = {'Info ', 'Warn ', 'Error', 'Debug'}
+M.levels = { 'Info ', 'Warn ', 'Error', 'Debug' }
 M.clock = fn.reltime()
 
 function M.set_silent(sl)
-    M.silent = sl
+  M.silent = sl
 end
 
 function M.set_verbose(vb)
-    M.verbose = vb
+  M.verbose = vb
 end
 
 function M.set_level(l)
+  -- the level only can be:
+  -- 0 : log debug, info, warn, error messages
+  -- 1 : log info, warn, error messages
+  -- 2 : log warn, error messages
+  -- 3 : log error messages
+  if l == 0 or l == 1 or l == 2 or l == 3 then
     M.level = l
+  end
 end
 
 function M._build_msg(msg, l)
-    msg = msg or ''
+  msg = msg or ''
-    -- local time = fn.strftime('%H:%M:%S')
+  -- local time = fn.strftime('%H:%M:%S')
-    -- error(string.format("Tried to call API function with vim.fn: use vim.api.%s instead", key))
+  -- error(string.format("Tried to call API function with vim.fn: use vim.api.%s instead", key))
-    -- local log = '[ ' ..  M.name .. ' ] [' .. time .. '] [ ' .. M.levels[l] .. '] ' .. msg
+  -- local log = '[ ' ..  M.name .. ' ] [' .. time .. '] [ ' .. M.levels[l] .. '] ' .. msg
-    -- change the format to 
+  -- change the format to
-    -- [ name ] [00:00:00:000] [level] msg
+  -- [ name ] [00:00:00:000] [level] msg
-    local clock = fn.reltimefloat(fn.reltime(M.clock))
+  local clock = fn.reltimefloat(fn.reltime(M.clock))
-    local h = fn.float2nr(clock / 60 / 60)
+  local h = fn.float2nr(clock / 60 / 60)
-    local m = fn.float2nr(clock / 60)
+  local m = fn.float2nr(clock / 60)
-    local s = fn.float2nr(clock) % 60
+  local s = fn.float2nr(clock) % 60
-    local mic = string.format('%00.3f', clock - fn.float2nr(clock))
+  local mic = string.format('%00.3f', clock - fn.float2nr(clock))
-    local c = string.format('%02d:%02d:%02d:%s', h, m, s, string.sub(mic, 3, -1))
+  local c = string.format('%02d:%02d:%02d:%s', h, m, s, string.sub(mic, 3, -1))
-    local log = string.format('[ %s ] [%s] [ %s ] %s',
+  local log = string.format('[ %s ] [%s] [ %s ] %s', M.name, c, M.levels[l], msg)
-        M.name,
+  return log
-        c,
-        M.levels[l],
-        msg)
-    return log
 end
 
 function M.debug(msg)
-    if M.level <= 0 then
+  if M.level <= 0 then
-        local log = M._build_msg(msg, 4)
+    local log = M._build_msg(msg, 4)
-        if M.silent == 0 and M.verbose >= 4 then
+    if M.silent == 0 and M.verbose >= 4 then
-            cmd('echom "' .. log .. '"')
+      cmd('echom "' .. log .. '"')
-        end
-        M.write(log)
     end
+    M.write(log)
+  end
 end
 
 function M.error(msg)
-    local log = M._build_msg(msg, 3)
+  local log = M._build_msg(msg, 3)
-    if M.silent == 0 and M.verbose >= 1 then
+  if M.silent == 0 and M.verbose >= 1 then
-        cmd('echohl Error')
+    cmd('echohl Error')
-        cmd('echom "' .. log .. '"')
+    cmd('echom "' .. log .. '"')
-        cmd('echohl None')
+    cmd('echohl None')
-    end
+  end
-    M.write(log)
+  M.write(log)
 end
 
 function M.write(msg)
-    table.insert(M.temp, msg)
+  table.insert(M.temp, msg)
-    if M.file ~= '' then
+  if M.file ~= '' then
-        if fn.isdirectory(fn.fnamemodify(M.file, ':p:h')) == 0 then
+    if fn.isdirectory(fn.fnamemodify(M.file, ':p:h')) == 0 then
-            fn.mkdir(fn.expand(fn.fnamemodify(M.file, ':p:h')), 'p')
+      fn.mkdir(fn.expand(fn.fnamemodify(M.file, ':p:h')), 'p')
-        end
-        local flags = ''
-        if fn.filereadable(M.file) == 1 then
-            flags = 'a'
-        end
-        fn.writefile({msg}, M.file, flags)
     end
-
+    local flags = ''
+    if fn.filereadable(M.file) == 1 then
+      flags = 'a'
+    end
+    fn.writefile({ msg }, M.file, flags)
+  end
 end
 
 function M.warn(msg, ...)
-    if M.level <= 2 then
+  if M.level <= 2 then
-        local log = M._build_msg(msg, 2)
+    local log = M._build_msg(msg, 2)
-        if (M.silent == 0 and M.verbose >= 2) or select(1, ...) == 1 then
+    if (M.silent == 0 and M.verbose >= 2) or select(1, ...) == 1 then
-            cmd('echohl WarningMsg')
+      cmd('echohl WarningMsg')
-            cmd('echom "' .. log .. '"')
+      cmd('echom "' .. log .. '"')
-            cmd('echohl None')
+      cmd('echohl None')
-        end
-        M.write(log)
     end
+    M.write(log)
+  end
 end
 
 function M.info(msg)
-    if M.level <= 1 then
+  if M.level <= 1 then
-        local log = M._build_msg(msg, 1)
+    local log = M._build_msg(msg, 1)
-        if M.silent == 0 and M.verbose >= 3 then
+    if M.silent == 0 and M.verbose >= 3 then
-            cmd('echom "' .. log .. '"')
+      cmd('echom "' .. log .. '"')
-        end
-        M.write(log)
     end
+    M.write(log)
+  end
 end
 
 function M.view(l)
-    local info = ''
+  local info = ''
-    local logs = ''
+  local logs = ''
-    if fn.filereadable(M.file) == 1 then
+  if fn.filereadable(M.file) == 1 then
-        logs = fn.readfile(M.file, '')
+    logs = fn.readfile(M.file, '')
-        info = info .. fn.join(fn.filter(logs, 'self._comp(v:val, a:l)'), "\n")
+    info = info .. fn.join(fn.filter(logs, 'self._comp(v:val, a:l)'), '\n')
-    else
+  else
-        info = info .. '[ ' .. M.name .. ' ] : logger file ' .. M.file
+    info = info
-        .. ' does not exists, only log for current process will be shown!'
+      .. '[ '
-        ..  "\n"
+      .. M.name
-        for key, value in pairs(M.temp) do
+      .. ' ] : logger file '
-            if M._comp(value, l) == 1 then
+      .. M.file
-                info = info .. value .. "\n"
+      .. ' does not exists, only log for current process will be shown!'
-            end
+      .. '\n'
-        end
+    for key, value in pairs(M.temp) do
+      if M._comp(value, l) == 1 then
+        info = info .. value .. '\n'
+      end
     end
-    return info
+  end
-
+  return info
 end
 
 function M._comp(msg, l)
-    -- if a:msg =~# '\[ ' . self.name . ' \] \[\d\d\:\d\d\:\d\d\] \[ '
+  -- if a:msg =~# '\[ ' . self.name . ' \] \[\d\d\:\d\d\:\d\d\] \[ '
-    if string.find(msg, M.levels[2]) ~= nil then
+  if string.find(msg, M.levels[2]) ~= nil then
-        return 1
+    return 1
-    elseif string.find(msg, M.levels[1]) ~= nil then
+  elseif string.find(msg, M.levels[1]) ~= nil then
-        if l > 2 then return 0 else return 1 end
+    if l > 2 then
+      return 0
     else
-        if l > 1 then return 0 else return 1 end
+      return 1
     end
+  else
+    if l > 1 then
+      return 0
+    else
+      return 1
+    end
+  end
 end
 
 function M.set_name(name)
-    M.name = name
+  M.name = name
 end
 
 function M.get_name()
-    return M.name
+  return M.name
 end
 
 function M.set_file(file)
-    M.file = file
+  M.file = file
 end
 
-
-
 return M

lua/spacevim/logger.lua

@@ -6,7 +6,6 @@
 -- License: GPLv3
 --=============================================================================
 
-
 local M = {}
 
 local logger = require('spacevim.api').import('logger')
@@ -15,9 +14,9 @@ local call = require('spacevim').call
 local echo = require('spacevim').echo
 local fn = nil
 if vim.fn == nil then
-    fn = require('spacevim').fn
+  fn = require('spacevim').fn
 else
-    fn = vim.fn
+  fn = vim.fn
 end
 
 logger.set_name('SpaceVim')
@@ -25,115 +24,126 @@ logger.set_level(1)
 logger.set_silent(1)
 logger.set_verbose(1)
 
-
-
 function M.info(msg)
-    logger.info(msg)
+  logger.info(msg)
 end
 
 function M.warn(msg, ...)
-    logger.warn(msg, ...)
+  logger.warn(msg, ...)
 end
 
 function M.error(msg)
-    logger.error(msg)
+  logger.error(msg)
 end
 
 function M.debug(msg)
-    logger.debug(msg)
+  logger.debug(msg)
 end
 
 function M.setLevel(level)
-    logger.set_level(level)
+  logger.set_level(level)
 end
 
 function M.setOutput(file)
-    logger.set_file(file)
+  logger.set_file(file)
 end
 
 function M.viewRuntimeLog()
-    local info = "### SpaceVim runtime log :\n\n"
+  local info = '### SpaceVim runtime log :\n\n' .. logger.view(logger.level)
-    .. logger.view(logger.level)
+  cmd('tabnew')
-    cmd('tabnew')
+  cmd('setl nobuflisted')
-    cmd('setl nobuflisted')
+  cmd('nnoremap <buffer><silent> q :tabclose!<CR>')
-    cmd('nnoremap <buffer><silent> q :tabclose!<CR>')
+  -- put info into buffer
-    -- put info into buffer
+  fn.append(0, fn.split(info, '\n'))
-    fn.append(0, fn.split(info, "\n"))
+  cmd('setl nomodifiable')
-    cmd('setl nomodifiable')
+  cmd('setl buftype=nofile')
-    cmd('setl buftype=nofile')
+  cmd('setl filetype=SpaceVimLog')
-    cmd('setl filetype=SpaceVimLog')
+  -- M.syntax_extra()
-    -- M.syntax_extra()
 end
 
 function M.viewLog(...)
-    local argvs={...}
+  local argvs = { ... }
-    local info = "<details><summary> SpaceVim debug information </summary>\n\n"
+  local info = '<details><summary> SpaceVim debug information </summary>\n\n'
-    .. "### SpaceVim options :\n\n"
+    .. '### SpaceVim options :\n\n'
-    .. "```toml\n"
+    .. '```toml\n'
-    .. fn.join(call('SpaceVim#options#list'), "\n")
+    .. fn.join(call('SpaceVim#options#list'), '\n')
-    .. "\n```\n"
+    .. '\n```\n'
-    .. "\n\n"
+    .. '\n\n'
-    .. "### SpaceVim layers :\n\n"
+    .. '### SpaceVim layers :\n\n'
     .. call('SpaceVim#layers#report')
-    .. "\n\n"
+    .. '\n\n'
-    .. "### SpaceVim Health checking :\n\n"
+    .. '### SpaceVim Health checking :\n\n'
     .. call('SpaceVim#health#report')
-    .. "\n\n"
+    .. '\n\n'
-    .. "### SpaceVim runtime log :\n\n"
+    .. '### SpaceVim runtime log :\n\n'
-    .. "```log\n"
+    .. '```log\n'
     .. logger.view(logger.level)
-    .. "\n```\n</details>\n\n"
+    .. '\n```\n</details>\n\n'
-    if argvs ~= nil and #argvs >= 1 then
+  if argvs ~= nil and #argvs >= 1 then
-        local bang = argvs[1]
+    local bang = argvs[1]
-        if bang == 1 then
+    if bang == 1 then
-            cmd('tabnew')
+      cmd('tabnew')
-            cmd('setl nobuflisted')
+      cmd('setl nobuflisted')
-            cmd('nnoremap <buffer><silent> q :tabclose!<CR>')
+      cmd('nnoremap <buffer><silent> q :tabclose!<CR>')
-            -- put info into buffer
+      -- put info into buffer
-            fn.append(0, fn.split(info, "\n"))
+      fn.append(0, fn.split(info, '\n'))
-            cmd('setl nomodifiable')
+      cmd('setl nomodifiable')
-            cmd('setl buftype=nofile')
+      cmd('setl buftype=nofile')
-            cmd('setl filetype=markdown')
+      cmd('setl filetype=markdown')
-        else
-            echo(info)
-        end
     else
-        return info
+      echo(info)
     end
+  else
+    return info
+  end
 end
 
 function M.syntax_extra()
-    fn.matchadd('ErrorMsg','.*[\\sError\\s\\].*')
+  fn.matchadd('ErrorMsg', '.*[\\sError\\s\\].*')
-    fn.matchadd('WarningMsg','.*[\\sWarn\\s\\].*')
+  fn.matchadd('WarningMsg', '.*[\\sWarn\\s\\].*')
 end
 
 function M.derive(name)
-    local derive = {}
+  local derive = {
-    derive['origin_name'] = logger.get_name()
+    origin_name = logger.get_name(),
+    _debug_mode = false,
+    derive_name = fn.printf('%' .. fn.strdisplaywidth(logger.get_name()) .. 'S', name),
+  }
 
-    function derive.info(msg)
+  function derive.info(msg)
-        logger.set_name(derive.derive_name)
+    logger.set_name(derive.derive_name)
-        logger.info(msg)
+    logger.info(msg)
-        logger.set_name(derive.origin_name)
+    logger.set_name(derive.origin_name)
-    end
+  end
-    function derive.warn(msg)
+  function derive.warn(msg)
-        logger.set_name(derive.derive_name)
+    logger.set_name(derive.derive_name)
-        logger.warn(msg)
+    logger.warn(msg)
-        logger.set_name(derive.origin_name)
+    logger.set_name(derive.origin_name)
-    end
+  end
-    function derive.error(msg)
+  function derive.error(msg)
-        logger.set_name(derive.derive_name)
+    logger.set_name(derive.derive_name)
-        logger.error(msg)
+    logger.error(msg)
-        logger.set_name(derive.origin_name)
+    logger.set_name(derive.origin_name)
-    end
+  end
 
-    function derive.debug(msg)
+  function derive.debug(msg)
-        logger.set_name(derive.derive_name)
+    if derive._debug_mode then
-        logger.debug(msg)
+      logger.set_name(derive.derive_name)
-        logger.set_name(derive.origin_name)
+      logger.debug(msg)
+      logger.set_name(derive.origin_name)
     end
-    derive['derive_name'] = fn.printf('%' .. fn.strdisplaywidth(logger.get_name()) .. 'S', name)
+  end
-    return derive
+  function derive.start_debug()
+    derive._debug_mode = true
+  end
+  function derive.stop_debug()
+    derive._debug_mode = false
+  end
+  function derive.enabled() -- {{{
+    return derive._debug_mode
+  end
+  -- }}}
+  return derive
 end
 
 return M