Automated tag generation and syntax highlighting in Vim
Vim has long been my favorite text editor and combined with Exuberant Ctags it has the potential to provide most of what I expect from an integrated development environment. Exuberant Ctags is the latest incarnation of a family of computer programs that scan source code files to create an index of identifiers (tags) and where they are defined. Vim uses this index (a so-called tags file) to enable you to jump to the definition of any identifier using the Control-] mapping.
When you're familiar with integrated development environments you may recognize this feature as "Go-to definition". One advantage of the combination of Vim and Exuberant Ctags over integrated development environments is that Vim supports syntax highlighting for over 500 file types (!) and Exuberant Ctags can generate tags for over 40 file types as well...
There's just one problem: You have to manually keep your tags files up-to-date and this turns out to be a royal pain in the ass! So I set out to write a Vim plug-in that would do this boring work for me. When I finished the plug-in's basic functionality (one automatic command and a call to system() later) I became interested in dynamic syntax highlighting, so I added that as well to see if it would work -- surprisingly well I'm happy to report!
Unzip the most recent ZIP archive file 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). Now try it out: Edit any file type supported by Exuberant Ctags and within ten seconds the plug-in should create/update your tags file (
~/.vimtags on UNIX,
~/_vimtags on Windows) with the tags defined in the file you just edited! This means that whatever file you're editing in Vim (as long as it's on the local file system), tags will always be available by the time you need them!
Additionally if the file you just opened is an AWK, C#, C, C++, Objective-C, Java, Lua, PHP, Python, Ruby, Shell, Tcl or Vim source file you should also notice that the function and type names defined in the file have been syntax highlighted.
easytags.vim plug-in is intended to work automatically once it's installed, but if you want to change how it works there are several options you can change and commands you can execute from your own mappings and/or automatic commands. These are all documented below.
Note that if the plug-in warns you
ctags isn't installed you'll have to download it from its homepage, or if you're running Debian/Ubuntu you can install it by executing the following shell command:
$ sudo apt-get install exuberant-ctags
A note about Windows
On Windows the system() function used by
easytags.vim causes a command prompt window to pop up while Exuberant Ctags is executing. If this bothers you then you can install my shell.vim plug-in which includes a DLL that works around this issue. Once you've installed both plug-ins it should work out of the box! Please let me know if this doesn't work for you.
This command executes Exuberant Ctags from inside Vim to update the global tags file defined by
g:easytags_file. When no arguments are given the tags for the current file are updated, otherwise the arguments are passed on to
ctags. For example when you execute the Vim command
:UpdateTags -R ~/.vim (or
:UpdateTags -R ~\vimfiles on Windows) the plug-in will execute
ctags -R ~/.vim for you (with some additional arguments, see the troubleshooting section "
:HighlightTags only works for the tags file created by
:UpdateTags" for more information).
When you execute this command like
:UpdateTags! (including the bang!) then all tags whose files are missing will be filtered from the global tags file.
Note that this command will be executed automatically every once in a while, assuming you haven't changed
When you execute this command while editing one of the supported file types (see above) the relevant tags in the current file are highlighted. The tags to highlight are gathered from all tags files known to Vim (through the 'tags' option).
Note that this command will be executed automatically every once in a while, assuming you haven't changed
The easytags plug-in should work out of the box but if you don't like the default configuration you can change how it works by setting the variables documented below. Most of these variables can also be changed for specific files by setting a buffer local variable instead of the global variable. For example to disable automatic highlighting (enabled by default) only in Python files you can add the following line to your vimrc script:
:autocmd FileType python let b:easytags_auto_highlight = 0
Note that buffer local variables always override global variables, so if you want to undo this for a specific file you have to use :unlet:
The plug-in will try to determine the location where Exuberant Ctags is installed on its own but this might not always work because any given executable named
ctags in your
$PATH might not in fact be Exuberant Ctags but some older, more primitive
ctags implementation which doesn't support the same command line options and thus breaks the easytags plug-in. If this is the case you can set the global variable
g:easytags_cmd to the location where you've installed Exuberant Ctags, e.g.:
:let g:easytags_cmd = '/usr/local/bin/ctags'
As mentioned above the plug-in will store your tags in
~/.vimtags on UNIX and
~/_vimtags on Windows. To change the location of this file, set the global variable
:let g:easytags_file = '~/.vim/tags'
~ in the
g:easytags_file variable is expanded to your current home directory (
$HOME on UNIX,
%USERPROFILE% on Windows).
:UpdateTags only writes to the global tags file, but it can be configured to look for project specific tags files by adding the following lines to your vimrc script:
:set tags=./tags; :let g:easytags_dynamic_files = 1
You can change the name of the tags file, the important thing is that it's relative to your working directory or the buffer (using a leading
g:easytags_dynamic_files is set to 1 the easytags plug-in will write to the first existing tags file seen by Vim (based on the 'tags' option). In other words: If a project specific tags file is found it will be used, otherwise the plug-in falls back to the global tags file (or a file type specific tags file).
If you set
g:easytags_dynamic_files to 2 the easytags plug-in will automatically create project specific tags based on the first name in the 'tags' option. This disables the global tags file and file type specific tags files.
The 'tags' option is reevaluated each time the plug-in runs, so which tags file is selected can differ depending on the buffer and working directory.
By default all tags are stored in a global tags file. When the tags file grows beyond a certain size Vim will be slowed down by the easytags plug-in because it has to read and process a large number of tags very frequently.
To avoid this problem you can set
g:easytags_by_filetype to the path of an existing directory. The easytags plug-in will create separate tags files for each file type in the configured directory. These tags files are automatically registered by the easytags plug-in when the file type of a buffer is set.
Note that the
g:easytags_dynamic_files option takes precedence over this option.
If you already have a global tags file you can create file type specific tags files from the global tags file using the command
By default the plug-in automatically generates and highlights tags when you stop typing for a few seconds (this works using the CursorHold automatic command). This means that when you edit a file, the dynamic highlighting won't appear until you pause for a moment. If you don't like this you can configure the plug-in to always enable dynamic highlighting:
:let g:easytags_always_enabled = 1
Be warned that after setting this option you'll probably notice why it's disabled by default: Every time you edit a file in Vim, the plug-in will first run Exuberant Ctags and then highlight the tags, and this slows Vim down quite a lot. I have some ideas on how to improve this latency by running Exuberant Ctags in the background so stay tuned!
Note: If you change this option it won't apply until you restart Vim, so you'll have to set this option in your vimrc script.
As I explained above the plug-in by default doesn't update or highlight your tags until you stop typing for a moment. The plug-in tries hard to do the least amount of work possible in this break but it might still interrupt your workflow. If it does you can disable the periodic update:
:let g:easytags_on_cursorhold = 0
Note: Like the
g:easytags_always_enabled option, if you change this option it won't apply until you restart Vim, so you'll have to set this option in your vimrc script.
Vim has a setting which influences how often the plug-in is automatically executed. When this setting is too low, the plug-in can break. For this reason the plug-in warns you when 'updatetime' is lower than 4000 milliseconds. If you really want the plug-in to be executed more than once every 4 seconds (without a warning) you can lower the minimum acceptable updatetime by setting this option (number of milliseconds).
Other plug-ins may lower the 'updatetime' value in certain contexts, e.g. insert mode in the case of the neocomplcache plug-in. By setting this option to 1 (true) you can configure the easytags plug-in so that it doesn't give warnings about the updatetime option but instead skip updating and highlighting while the updatetime is set too low. When the updatetime is restored to a reasonable value the plug-in resumes.
By default the plug-in automatically updates and highlights your tags when you stop typing for a moment. If you want to disable automatic updating while keeping automatic highlighting enabled you can set this option to false:
:let g:easytags_auto_update = 0
By default the plug-in automatically updates and highlights your tags when you stop typing for a moment. If you want to disable automatic highlighting while keeping automatic updating enabled you can set this option to false:
:let g:easytags_auto_highlight = 0
:UpdateTags command is executed automatically or without arguments, it defaults to updating just the tags for the current file. If you'd rather have it recursively scan everything below the directory of the current file then set this option to true (1):
:let g:easytags_autorecurse = 1
You have to explicitly enable this option because it should only be used while navigating around small directory trees. Imagine always having this option enabled and then having to edit a file in e.g. the root of your home directory: The
easytags.vim plug-in would freeze Vim for a long time while you'd have to wait for Exuberant Ctags to scan thousands of files...
Note that when you enable this option the
easytags.vim plug-in might ignore other options like
g:easytags_resolve_links. This is an implementation detail which I intend to fix.
Exuberant Ctags knows how to generate tags for struct/class members in C++ and Java source code but doesn't do so by default because it can more than double the size of your tags files, thus taking much longer to read/write the tags file. When you enable the
g:easytags_include_members option from your vimrc script (before the
easytags.vim plug-in is loaded):
:let g:easytags_include_members = 1
Exuberant Ctags will be instructed to include struct/class members using the
--extra=+q command line argument and the
easytags.vim plug-in will highlight them using the
cMember highlighting group. Because most color schemes don't distinguish the Identifier and Type highlighting groups all members will now probably look like type definitions. You can change that by executing either of the following Vim commands (from your vimrc script, a file type plug-in, etc.):
" If you like one of the existing styles you can link them: highlight link cMember Special " You can also define your own style if you want: highlight cMember gui=italic
UNIX has symbolic links and hard links, both of which conflict with the concept of having one unique location for every identifier. With regards to hard links there's not much anyone can do, but because I use symbolic links quite a lot I've added this option. It's disabled by default since it has a small performance impact and might not do what unknowing users expect it to: When you enable this option the plug-in will resolve symbolic links in pathnames, which means your tags file will only contain entries with canonical pathnames. To enable this option (which I strongly suggest doing when you run UNIX and use symbolic links) execute the following Vim command:
:let g:easytags_resolve_links = 1
If this is set and not false, it will suppress the warning on startup if ctags is not found or not recent enough.
:let g:easytags_suppress_ctags_warning = 1
This variable is a string of comma separated names of syntax groups in which dynamic highlighting is not applied. It defaults to
Faster syntax highlighting using Python
The Vim script implementation of dynamic syntax highlighting is quite slow on large tags files. When the Python Interface to Vim is enabled the easytags plug-in will therefor automatically use a Python script that performs dynamic syntax highlighting about twice as fast as the Vim script implementation. The following options are available to change the default configuration.
To disable the Python implementation of dynamic syntax highlighting you can set this option to false (0).
This option defines the pathname of the script that contains the Python implementation of dynamic syntax highlighting.
How to customize the highlighting colors?
The easytags plug-in defines new highlighting groups for dynamically highlighted tags. These groups are linked to Vim's default groups so that they're colored out of the box, but if you want you can change the styles. To do so use a
highlight command such as the ones given a few paragraphs back. Of course you'll need to change the group name. Here are the group names used by the easytags plug-in:
- C, C++, Objective C:
As you can see each of these names ends in
Tag to avoid conflicts with the syntax modes shipped with Vim. And about the singular/plural confusion: I've tried to match the existing highlighting groups defined by popular syntax modes (except of course for the
Passing custom command line arguments to Exuberant Ctags
You may want to run Exuberant Ctags with specific command line options, for example the code_complete plug-in requires the signature field to be present. To do this you can create a configuration file for Exuberant Ctags, e.g.
~/.ctags on UNIX or
%USERPROFILE%\ctags.cnf on Windows. The file should contain one command line option per line. See the Exuberant Ctags manual for details.
:HighlightTags only works for the tags file created by
If you want to create tags files and have their tags highlighted by the
easytags.vim plug-in then you'll have to create the tags file with certain arguments to Exuberant Ctags:
$ ctags --fields=+l --c-kinds=+p --c++-kinds=+p ...
--fields=+l argument makes sure that Exuberant Ctags includes a
language:... property with each entry in the tags file. This is required by the
:HighlightTags command so it can filter tags by their file type. The other two arguments make sure Exuberant Ctags generates tags for function prototypes in C/C++ source code.
If you have the
g:easytags_include_members option enabled (its off by default) then you'll also need to add the
--extra=+q argument so that Exuberant Ctags generates tags for structure/class members.
The plug-in complains that Exuberant Ctags isn't installed
After a Mac OS X user found out the hard way that the
ctags executable isn't always Exuberant Ctags and we spend a few hours debugging the problem I added proper version detection: The plug-in executes
ctags --version when Vim is started to verify that Exuberant Ctags 5.5 or newer is installed. If it isn't Vim will show the following message on startup:
easytags.vim: Plug-in not loaded because Exuberant Ctags isn't installed! Please download & install Exuberant Ctags from http://ctags.sf.net
If the installed Exuberant Ctags version is too old the plug-in will complain:
easytags.vim: Plug-in not loaded because Exuberant Ctags 5.5 or newer is required while you have version %s installed!
If you have the right version of Exuberant Ctags installed but the plug-in still complains, try executing the following command from inside Vim:
If this doesn't print the location where you installed Exuberant Ctags it means your system already had a
ctags executable but it isn't compatible with Exuberant Ctags 5.5 and you'll need to set the
g:easytags_cmd option (see above) so the plug-in knows which
ctags to run.
Vim locks up while the plug-in is running
Once or twice now in several years I've experienced Exuberant Ctags getting into an infinite loop when given garbage input. In my case this happened by accident a few days ago :-|. Because my plug-in executes
ctags in the foreground this will block Vim indefinitely! If this happens you might be able to kill
ctags by pressing Control-C but if that doesn't work you can also kill it without stopping Vim using a task manager or the
pkill command (available on most UNIX systems):
$ pkill -KILL ctags
If Vim seems very slow and you suspect this plug-in might be the one to blame, increase Vim's verbosity level:
Every time the plug-in executes it will time how long the execution takes and add the results to Vim's message history, which you can view by executing the :messages command.
Failed to highlight tags because pattern is too big!
easytags.vim plug-in fails to highlight your tags and the error message mentions that the pattern is too big, your tags file has grown too large for Vim to be able to highlight all tagged identifiers! I've had this happen to me with 50 KB patterns because I added most of the headers in
/usr/include/ to my tags file. Internally Vim raises the error E339: Pattern too long and unfortunately the only way to avoid this problem once it occurs is to reduce the number of tagged identifiers...
In my case the solution was to move most of the tags from
/usr/include/ over to project specific tags files which are automatically loaded by Vim when I edit files in different projects because I've set the 'tags' option as follows:
Once you've executed the above command, Vim will automatically look for a file named
.tags in the directory of the current file. Because of the
; Vim also recurses upwards so that you can nest files arbitrarily deep under your project directories.
The plug-in doesn't seem to work in Cygwin
If you want to use the plug-in with Vim under Cygwin, you need to have the Cygwin version of Ctags installed instead of the Windows version (thanks to Alex Zuroff for reporting this!).
If you have questions, bug reports, suggestions, etc. the author can be contacted at firstname.lastname@example.org. The latest version is available at http://peterodding.com/code/vim/easytags/ and http://github.com/xolox/vim-easytags. If you like this plug-in please vote for it on Vim Online.