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Semantic highlighting for Lua in Vim

The Vim plug-in luainspect.vim uses the [LuaInspect] lua-inspect tool to (automatically) perform semantic highlighting of variables in Lua source code. It was inspired by lua2-mode lua2-mode (for Emacs emacs) and the SciTE scite plug-in included with LuaInspect. In addition to the semantic highlighting the following features are currently supported:

  • Press <F2> with the text cursor on a variable and the plug-in will prompt you to rename the variable.

  • Press gd (in normal mode) with the text cursor on a variable and you'll jump to its declaration / first occurrence.

  • When you hover over a variable with the mouse cursor in graphical Vim, information about the variable is displayed in a tooltip.

  • If the text cursor is on a variable while the highlighting is refreshed then all occurrences of the variable will be marked in the style of [Vim's cursorline option] cursorline.

  • When luainspect reports a wrong argument count for a function call the text will be highlighted with a green underline. When you hover over the highlighted text a tooltip shows the associated warning message.

  • When LuaInspect reports warnings about unused variables, wrong argument counts, etc. they are shown in a [location list window] location-list.

  • When a syntax error is found (during highlighting or using the rename functionality) the lines where the error is reported will be marked like a spelling error.

Screenshot of semantic highlighting


Please note that the vim-lua-inspect plug-in requires my vim-misc plug-in which is separately distributed.

Unzip the most recent ZIP archives of the [vim-lua-inspect] download-lua-inspect and [vim-misc] download-misc plug-ins inside your Vim profile directory (usually this is ~/.vim on UNIX and %USERPROFILE%\vimfiles on Windows), restart Vim and execute the command :helptags ~/.vim/doc (use :helptags ~\vimfiles\doc instead on Windows).

If you prefer you can also use Pathogen pathogen, Vundle vundle or a similar tool to install & update the [vim-lua-inspect] github-lua-inspect and [vim-misc] github-misc plug-ins using a local clone of the git repository.

Now try it out: Edit a Lua file and within a few seconds semantic highlighting should be enabled automatically!

Note that on Windows a command prompt window pops up whenever LuaInspect is run as an external process. If this bothers you then you can install my [shell.vim] vim-shell plug-in which includes a DLL dll that works around this issue. Once you've installed both plug-ins it should work out of the box!


When you open any Lua file the semantic highlighting should be enabled automatically within a few seconds, so you don't have to configure anything if you're happy with the defaults.


The :LuaInspect command

You don't need to use this command unless you've disabled automatic highlighting using g:lua_inspect_events. When you execute this command the plug-in runs the LuaInspect tool and then highlights all variables in the current buffer using one of the following highlighting groups:

  • luaInspectGlobalDefined
  • luaInspectGlobalUndefined
  • luaInspectLocalUnused
  • luaInspectLocalMutated
  • luaInspectUpValue
  • luaInspectParam
  • luaInspectLocal
  • luaInspectFieldDefined
  • luaInspectFieldUndefined
  • luaInspectSelectedVariable
  • luaInspectWrongArgCount
  • luaInspectSyntaxError

If you don't like one or more of the default styles the Vim documentation [describes how to change them] hi-default. If you want to disable the semantic highlighting in a specific Vim buffer execute :LuaInspect! in that buffer. When you want to re-enable the highlighting execute :LuaInspect again, but now without the [bang (!)] bang.

The :LuaInspectToggle command

By default the semantic highlighting and the warning messages in the location list window are automatically applied to Lua buffers and updated every once in a while, but this can be disabled by setting g:lua_inspect_events to an empty string in your [vimrc script] vimrc. If the plug-in is not automatically enabled then it may be useful to enable/disable it using a key mapping. That's what the :LuaInspectToggle command is for. You still have to define your key mapping of choice in your [vimrc script] vimrc though. For example:

" Don't enable the lua-inspect plug-in automatically in Lua buffers.
let g:lua_inspect_events = ''

" Enable/disable the lua-inspect plug-in manually using <F6>.
imap <F6> <C-o>:LuaInspectToggle<CR>
nmap <F6>      :LuaInspectToggle<CR>

The :LuaInspectRename command

This command renames the variable under the cursor. It's used to define the <F2> mapping and can be used if you don't like the default mappings and want to define your own.

The :LuaInspectGoTo command

This command jumps to the definition of the variable under the cursor. It's used to define the gd mapping and can be used if you don't like the default mappings and want to define your own.


The g:loaded_luainspect option

This variable isn't really an option but if you want to avoid loading the luainspect.vim plug-in you can set this variable to any value in your [vimrc script] vimrc:

:let g:loaded_luainspect = 1

The g:lua_inspect_mappings option

If this is set to true (1, the default value) then the <F2> and gd mappings are defined in Lua buffers (as buffer local mappings). You can set it to false (0) to disable the default mappings (so you can define your own).

The g:lua_inspect_warnings option

When LuaInspect reports warnings about unused variables, wrong argument counts, etc. they are automatically shown in a [location list window] location-list. If you don't like this add the following to your [vimrc script] vimrc:

:let g:lua_inspect_warnings = 0

The g:lua_inspect_events option

By default semantic highlighting is automatically enabled after a short timeout and when you save a buffer. If you want to disable automatic highlighting altogether add the following to your [vimrc script] vimrc:

:let g:lua_inspect_events = ''

You can also add events, for example if you also want to run :LuaInspect the moment you edit a Lua file then try this:

:let g:lua_inspect_events = 'CursorHold,CursorHoldI,BufReadPost,BufWritePost'

Note that this only works when the plug-in is loaded (or reloaded) after setting the g:lua_inspect_events option.

The g:lua_inspect_internal option

The plug-in uses the Lua interface for Vim when available so that it doesn't have to run LuaInspect as an external program (which can slow things down). If you insist on running LuaInspect as an external program you can set this variable to false (0) in your [vimrc script] vimrc:

:let g:lua_inspect_internal = 0


If you have questions, bug reports, suggestions, etc. the author can be contacted at The latest version is available at and If you like this plug-in please vote for it on [Vim Online] vim-online.


This software is licensed under the [MIT license] mit. © 2014 Peter Odding <>.

The source code repository and distributions contain bundled copies of LuaInspect and Metalua, please refer to their licenses (also included).