YouCompleteMe/doc/youcompleteme.txt

*youcompleteme.txt*  YouCompleteMe: a code-completion engine for Vim

===============================================================================
                                                        *youcompleteme-contents*
Contents ~

 1. Introduction                                    |youcompleteme-introduction|
 2. Mac OS X super-quick installation |youcompleteme-mac-os-x-super-quick-installation|
 3. Ubuntu Linux x64 super-quick installation |youcompleteme-ubuntu-linux-x64-super-quick-installation|
 4. Windows Installation                    |youcompleteme-windows-installation|
 5. Full Installation Guide              |youcompleteme-full-installation-guide|
 6. User Guide                                        |youcompleteme-user-guide|
  1. General Usage                                 |youcompleteme-general-usage|
  2. Completion string ranking         |youcompleteme-completion-string-ranking|
  3. General Semantic Completion Engine Usage |youcompleteme-general-semantic-completion-engine-usage|
  4. C-family Semantic Completion Engine Usage |youcompleteme-c-family-semantic-completion-engine-usage|
  5. Syntastic integration                 |youcompleteme-syntastic-integration|
  6. Writing New Semantic Completers |youcompleteme-writing-new-semantic-completers|
 7. Commands                                            |youcompleteme-commands|
  1. The |YcmForceCompileAndDiagnostics| command
  2. The |YcmDiags| command
  3. The |YcmShowDetailedDiagnostic| command
  4. The |YcmDebugInfo| command
  5. The |YcmCompleter| command
 8. Options                                              |youcompleteme-options|
  1. The |g:ycm_min_num_of_chars_for_completion| option
  2. The |g:ycm_filetype_whitelist| option
  3. The |g:ycm_filetype_blacklist| option
  4. The |g:ycm_filetype_specific_completion_to_disable| option
  5. The |g:ycm_allow_changing_updatetime| option
  6. The |g:ycm_complete_in_comments_and_strings| option
  7. The |g:ycm_collect_identifiers_from_comments_and_strings| option
  8. The |g:ycm_add_preview_to_completeopt| option
  9. The |g:ycm_autoclose_preview_window_after_completion| option
  10. The |g:ycm_max_diagnostics_to_display| option
  11. The |g:ycm_key_list_select_completion| option
  12. The |g:ycm_key_list_previous_completion| option
  13. The |g:ycm_key_invoke_completion| option
  14. The |g:ycm_key_detailed_diagnostics| option
  15. The |g:ycm_global_ycm_extra_conf| option
  16. The |g:ycm_confirm_extra_conf| option
  17. The |g:ycm_extra_conf_globlist| option
  18. The |g:ycm_semantic_triggers| option
 9. FAQ                                                      |youcompleteme-faq|
  1. I get a linker warning regarding |libpython| on Mac when compiling YCM
  2. I get a weird window at the top of my file when I use the semantic engine
  3. It appears that YCM is not working
  4. I cannot get the Syntastic integration to work
  5. Sometimes it takes much longer to get semantic completions than normal
  6. YCM auto-inserts completion strings I don't want!
  7. I get a 'E227: mapping already exists for <blah>' error when I start Vim
  8. I'm trying to use a Homebrew Vim with YCM and I'm getting segfaults
  9. I have a Homebrew Python and/or MacVim; can't compile/SIGABRT when starting
  10. I get 'LONG_BIT definition appears wrong for platform' when compiling
  11. I get 'Vim: Caught deadly signal SEGV' on Vim startup
  12. Why isn't YCM just written in plain VimScript, FFS?
  13. Why does YCM demand such a recent version of Vim?
  14. I get annoying messages in Vim's status area when I type
  15. Nasty bugs happen if I have the |vim-autoclose| plugin installed
 10. Contact                                             |youcompleteme-contact|
 11. License                                             |youcompleteme-license|

===============================================================================
                                                    *youcompleteme-introduction*
Introduction ~

YouCompleteMe is a fast, as-you-type, fuzzy-search code completion engine for
Vim. It has several completion engines: an identifier-based engine that works
with every programming language, a semantic, Clang [1]-based engine that
provides native semantic code completion for C/C++/Objective-C/Objective-C++
(from now on referred to as "the C-family languages") and an omnifunc-based
completer that uses data from Vim's omnicomplete system to provide semantic
completions for many other languages (Python, Ruby, PHP etc.).

    YouCompleteMe GIF demo, see reference [2]

Here's an explanation of what happens in the short GIF demo above.

First, realize that no keyboard shortcuts had to be pressed to get the list of
completion candidates at any point in the demo. The user just types and the
suggestions pop up by themselves. If the user doesn't find the completion
suggestions relevant and/or just wants to type, he can do so; the completion
engine will not interfere.

When the user sees a useful completion string being offered, he presses the
TAB key to accept it. This inserts the completion string. Repeated presses of
the TAB key cycle through the offered completions.

If the offered completions are not relevant enough, the user can continue
typing to further filter out unwanted completions.

A critical thing to notice is that the completion filtering is NOT based on
the input being a string prefix of the completion (but that works too). The
input needs to be a subsequence [3] match of a completion. This is a fancy way
of saying that any input characters need to be present in a completion string
in the order in which they appear in the input. So 'abc' is a subsequence of
'xaybgc', but not of 'xbyxaxxc'. After the filter, a complicated sorting
system ranks the completion strings so that the most relevant ones rise to the
top of the menu (so you usually need to press TAB just once).

All of the above works with any programming language because of the
identifier-based completion engine. It collects all of the identifiers in the
current file and other files you visit and searches them when you type
(identifiers are put into per-filetype groups).

The demo also shows the semantic engine in use. When the user presses '.',
'->' or '::' while typing in insert mode, the semantic engine is triggered (it
can also be triggered with a keyboard shortcut; see the rest of the docs).

The last thing that you can see in the demo is YCM's integration with
Syntastic [4] (the little red X that shows up in the left gutter) if you are
editing a C-family file. As Clang compiles your file and detects warnings or
errors, they will be piped to Syntastic for display. You don't need to save
your file or press any keyboard shortcut to trigger this, it "just happens" in
the background.

In essence, YCM obsoletes the following Vim plugins because it has all of
their features plus extra:

 - clang_complete

 - AutoComplPop

 - Supertab

 - neocomplcache

===============================================================================
                               *youcompleteme-mac-os-x-super-quick-installation*
Mac OS X super-quick installation ~

Please refer to the full Installation Guide below; the following commands are
provided on a best-effort basis and may not work for you.

Install the latest version of MacVim [5]. Yes, MacVim. And yes, the latest.

If you don't use the MacVim GUI, it is recommended to use the Vim binary that
is inside the MacVim.app package ('MacVim.app/Contents/MacOS/Vim'). To ensure
it works correctly copy the 'mvim' script from the MacVim [5] download to your
local binary folder (for example '/usr/local/bin/mvim') and then symlink it:
>
    ln -s /usr/local/bin/mvim vim

Install YouCompleteMe with Vundle [6].

Remember: YCM is a plugin with a compiled component. If you update YCM using
Vundle and the ycm_core library API has changed (happens rarely), YCM will
notify you to recompile it. You should then rerun the install process.

It's recommended that you have the latest Xcode installed along with the
latest Command Line Tools (that you install from within Xcode).

Install CMake. Preferably with Homebrew [7], but here's the stand-alone CMake
installer [8].

If you have installed a Homebrew Python and/or Homebrew MacVim, see the FAQ
for details.

Compiling YCM with semantic support for C-family languages:
>
    cd ~/.vim/bundle/YouCompleteMe
    ./install.sh --clang-completer

Compiling YCM without semantic support for C-family languages:
>
    cd ~/.vim/bundle/YouCompleteMe
    ./install.sh

That's it. You're done. Refer to the User Guide section on how to use YCM.
Don't forget that if you want the C-family semantic completion engine to work,
you will need to provide the compilation flags for your project to YCM. It's
all in the User Guide.

YCM comes with sane defaults for its options, but you still may want to take a
look at what's available for configuration. There are a few interesting
options that are conservatively turned off by default that you may want to
turn on.

===============================================================================
                       *youcompleteme-ubuntu-linux-x64-super-quick-installation*
Ubuntu Linux x64 super-quick installation ~

Please refer to the full Installation Guide below; the following commands are
provided on a best-effort basis and may not work for you.

Make sure you have Vim 7.3.584 with python2 support. At the time of writing,
the version of Vim shipping with Ubuntu is too old. You may need to compile
Vim from source [9] (don't worry, it's easy).

Install YouCompleteMe with Vundle [6].

Remember: YCM is a plugin with a compiled component. If you update YCM using
Vundle and the ycm_core library API has changed (happens rarely), YCM will
notify you to recompile it. You should then rerun the install process.

Install development tools and CMake: 'sudo apt-get install build-essential
cmake'

Make sure you have Python headers installed: 'sudo apt-get install
python-dev'.

Compiling YCM with semantic support for C-family languages:
>
    cd ~/.vim/bundle/YouCompleteMe
    ./install.sh --clang-completer

Compiling YCM without semantic support for C-family languages:
>
    cd ~/.vim/bundle/YouCompleteMe
    ./install.sh

That's it. You're done. Refer to the User Guide section on how to use YCM.
Don't forget that if you want the C-family semantic completion engine to work,
you will need to provide the compilation flags for your project to YCM. It's
all in the User Guide.

YCM comes with sane defaults for its options, but you still may want to take a
look at what's available for configuration. There are a few interesting
options that are conservatively turned off by default that you may want to
turn on.

===============================================================================
                                            *youcompleteme-windows-installation*
Windows Installation ~

YCM has no official support for Windows, but that doesn't mean you can't get
it to work there. See the Windows Installation Guide [10] wiki page. Feel free
to add to it.

===============================================================================
                                         *youcompleteme-full-installation-guide*
Full Installation Guide ~

These are the steps necessary to get YCM working on a Unix OS like Linux or
Mac OS X. My apologies to Windows users, but I don't have a guide for them.
The code is platform agnostic, so if everything is configured correctly, YCM
should work on Windows without issues (but as of writing, it's untested on
that platform).

See the FAQ if you have any issues.

Remember: YCM is a plugin with a compiled component. If you update YCM using
Vundle and the ycm_core library API has changed (happens rarely), YCM will
notify you to recompile it. You should then rerun the install process.

Please follow the instructions carefully. Read EVERY WORD.

 - Ensure that your version of Vim is at least 7.3.584 and that it has support
   for python2 scripting. Inside Vim, type ':version'. Look at the first two
   to three lines of output; it should say 'Vi IMproved 7.3' and then below
   that, 'Included patches: 1-X', where X will be some number. That number
   needs to be 584 or higher. If your version of Vim is not recent enough, you
   may need to compile Vim from source [9] (don't worry, it's easy). After you
   have made sure that you have Vim 7.3.584+, type the following in Vim:
   ':echo has('python')'. The output should be 1. If it's 0, then get a
   version of Vim with Python support.

 - Install YCM with Vundle [6] (or Pathogen [11], but Vundle is a better idea).
   With Vundle, this would mean adding a 'Bundle 'Valloric/YouCompleteMe' line
   to your vimrc [12].

 - [Complete this step ONLY if you care about semantic completion support for
   C-family languages. Otherwise it's not neccessary.] Download the latest
   version of 'libclang'. Clang is an open-source compiler that can compile
   C/C++/Objective-C/Objective-C++. The 'libclang' library it provides is used
   to power the YCM semantic completion engine for those languages. YCM needs
   libclang version 3.2 or higher. You can use the system libclang only if you
   are sure it is version 3.2 or higher, otherwise don't. Even if it is, I
   recommend using the official binaries from llvm.org [13] if at all
   possible. Make sure you download the correct archive file for your OS.

 - Compile the 'ycm_core' plugin plugin (ha!) that YCM needs. This is the C++
   engine that YCM uses to get fast completions. You will need to have 'cmake'
   installed in order to generate the required makefiles. Linux users can
   install cmake with their package manager ('sudo apt-get install cmake' for
   Ubuntu) whereas other users can download and install [8] cmake from its
   project site. Mac users can also get it through Homebrew [7] with 'brew
   install cmake'. You also need to make sure you have Python headers
   installed. On a Debian-like Linux distro, this would be 'sudo apt-get
   install python-dev'. On Mac they should already be present. Here we'll
   assume you installed YCM with Vundle. That means that the top-level YCM
   directory is in '~/.vim/bundle/YouCompleteMe'. We'll create a new folder
   where build files will be placed. Run the following: cd ~ mkdir ycm_build
   cd ycm_build Now we need to generate the makefiles. If you DON'T care about
   semantic support for C-family languages, run the following command in the
   'ycm_build' directory: 'cmake -G "Unix Makefiles" . ~/.vim/bundle/YouCompleteMe/cpp'
   If you DO care about semantic support for C-family languages, then your
   'cmake' call will be a bit more complicated. We'll assume you downloaded a
   binary distribution of LLVM+Clang from llvm.org in step 3 and that you
   extracted the archive file to folder '~/ycm_temp/llvm_root_dir' (with
   'bin', 'lib', 'include' etc. folders right inside that folder). With that
   in mind, run the following command in the 'ycm_build' directory: 'cmake -G
   "Unix Makefiles" -DPATH_TO_LLVM_ROOT=~/ycm_temp/llvm_root_dir .
   ~/.vim/bundle/YouCompleteMe/cpp' Now that makefiles have been generated,
   simply run 'make ycm_core'. For those who want to use the system version of
   libclang, you would pass '-DUSE_SYSTEM_LIBCLANG=ON' to cmake instead of the
   '-DPATH_TO_LLVM_ROOT=...' flag. You could also force the use of a custom
   libclang library with '-DEXTERNAL_LIBCLANG_PATH=/path/to/libclang.so' flag
   (the library would end with '.dylib' on a Mac). Again, this flag would be
   used instead of the other flags.

 - [Complete this step ONLY if you care about semantic completion support for
   C-family languages. Otherwise it's not neccessary.] Copy the libclang
   library file into the 'YouCompleteMe/python' folder. The library file is
   'libclang.so' on Linux and 'libclang.dylib' on Mac. We'll assume you
   downloaded a binary distribution of LLVM+Clang from llvm.org in step 3 and
   that you extracted the archive file to folder '~/ycm_temp/llvm_root_dir'
   (with 'bin', 'lib', 'include' etc. folders right inside that folder). We'll
   also assume you installed YCM with Vundle. That means that the top-level
   YCM directory is in '~/.vim/bundle/YouCompleteMe'. On Linux, run: 'cp
   ~/ycm_temp/llvm_root_dir/lib/libclang.so ~/.vim/bundle/YouCompleteMe/python'
   On Mac, run: 'cp ~/ycm_temp/llvm_root_dir/lib/libclang.dylib
   ~/.vim/bundle/YouCompleteMe/python' DO NOT FORGET THIS STEP. If you forget
   to copy over 'libclang.so' version 3.2 into the 'YouCompleteMe/python'
   folder then YCM will not work if you selected C-family support during YCM
   compilation.

That's it. You're done. Refer to the User Guide section on how to use YCM.
Don't forget that if you want the C-family semantic completion engine to work,
you will need to provide the compilation flags for your project to YCM. It's
all in the User Guide.

YCM comes with sane defaults for its options, but you still may want to take a
look at what's available for configuration. There are a few interesting
options that are conservatively turned off by default that you may want to
turn on.

===============================================================================
                                                      *youcompleteme-user-guide*
User Guide ~

-------------------------------------------------------------------------------
                                                   *youcompleteme-general-usage*
General Usage ~

 - If the offered completions are too broad, keep typing characters; YCM will
   continue refining the offered completions based on your input.

 - Filtering is "smart-case" sensitive; if you are typing only lowercase
   letters, then it's case-insensitive. If your input involves uppercase
   letters, then it's case-sensitive. So "foo" matches "Foo" and "foo", but
   "Foo" matches "Foo" but not "foo".

 - Use the TAB key to accept a completion and continue pressing TAB to cycle
   through the completions. Use Shift-TAB to cycle backwards. Note that if
   you're using console Vim (that is, not Gvim or MacVim) then it's likely
   that the Shift-TAB binding will not work because the console will not pass
   it to Vim. You can remap the keys; see the options section below.

-------------------------------------------------------------------------------
                                       *youcompleteme-completion-string-ranking*
Completion string ranking ~

The subsequence filter removes any completions that do not match the input,
but then the sorting system kicks in. It's actually very complicated and uses
lots of factors, but suffice it to say that "word boundary" (WB) subsequence
character matches are "worth" more than non-WB matches. In effect, this means
given an input of "gua", the completion "getUserAccount" would be ranked
higher in the list than the "Fooguxa" completion (both of which are
subsequence matches). A word-boundary character are all capital characters,
characters preceded by an underscore and the first letter character in the
completion string.

-------------------------------------------------------------------------------
                        *youcompleteme-general-semantic-completion-engine-usage*
General Semantic Completion Engine Usage ~

 - You can use Ctrl+Space to trigger the completion suggestions anywhere, even
   without a string prefix. This is useful to see which top-level functions
   are available for use.

-------------------------------------------------------------------------------
                       *youcompleteme-c-family-semantic-completion-engine-usage*
C-family Semantic Completion Engine Usage ~

 - You really also want to install the latest version of the Syntastic [4] Vim
   plugin. It has support for YCM and together they will provide you with
   compile errors/warnings practically instantly and without saving the file.

YCM looks for a '.ycm_extra_conf.py' file in the directory of the opened file
or in any directory above it in the hierarchy (recursively); when the file is
found, it is loaded (only once!) as a Python module. YCM calls a
'FlagsForFile' method in that module which should provide it with the
information necessary to compile the current file. You can also provide a path
to a global '.ycm_extra_conf.py' file, which will be used as a fallback. To
prevent the execution of malicious code from a file you didn't write YCM will
ask you once per '.ycm_extra_conf.py' if it is safe to load. This can be
disabled and you can white-/blacklist files. See the Options section for more
details.

This system was designed this way so that the user can perform any arbitrary
sequence of operations to produce a list of compilation flags YCM should hand
to Clang.

See YCM's own '.ycm_extra_conf.py' [14] for details on how this works. You
should be able to use it as a starting point. Hint: just replace the strings
in the 'flags' variable with compilation flags necessary for your project.
That should be enough for 99% of projects.

Yes, Clang's 'CompilationDatabase' system [15] is also supported. Again, see
the above linked example file.

If Clang encounters errors when compiling the header files that your file
includes, then it's probably going to take a long time to get completions.
When the completion menu finally appears, it's going to have a large number of
unrelated completion strings (type/function names that are not actually
members). This is because Clang fails to build a precompiled preamble for your
file if there are any errors in the included headers and that preamble is key
to getting fast completions.

Call the ':YcmDiags' command to see if any errors or warnings were detected in
your file. Even better, use Syntastic.

-------------------------------------------------------------------------------
                                           *youcompleteme-syntastic-integration*
Syntastic integration ~

YCM has explicit support for Syntastic [4] (and vice-versa) if you compiled
YCM with Clang support; this means that any diagnostics (errors or warnings)
that Clang encounters while compiling your file will be fed back to Syntastic
for display.

YCM will recompile your file in the background 'updatetime' (see ':h
updatetime' in Vim) milliseconds after you stop typing (to be specific, on
'CursorHold' and 'CursorHoldI' Vim events). YCM will change your 'updatetime'
value to be '2000' milliseconds (there's an option to tell it not to do this
if you wish).

The new diagnostics (if any) will be fed back to Syntastic the next time you
press any key on the keyboard. So if you stop typing and just wait for the new
diagnostics to come in, that will not work. You need to press some key for the
GUI to update.

Having to press a key to get the updates is unfortunate, but cannot be changed
due to the way Vim internals operate; there is no way that a background task
can update Vim's GUI after it has finished running. You have to press a key.
This will make YCM check for any pending diagnostics updates.

You can force a full, blocking compilation cycle with the ':YcmForceCompileAndDiagnostics'
command (you may want to map that command to a key; try putting 'nnoremap <F5>
:YcmForceCompileAndDiagnostics<CR>' in your vimrc). Calling this command will
force YCM to immediately recompile your file and display any new diagnostics
it encounters. Do note that recompilation with this command may take a while
and during this time the Vim GUI will be blocked.

After the errors are displayed by Syntastic, it will display a short
diagnostic message when you move your cursor to the line with the error. You
can get a detailed diagnostic message with the '<leader>d' key mapping (can be
changed in the options) YCM provides when your cursor is on the line with the
diagnostic.

You can also see the full diagnostic message for all the diagnostics in the
current file in Vim's 'locationlist', which can be opened with the ':lopen'
and ':lclose' commands. A good way to toggle the display of the 'locationlist'
with a single key mapping is provided by another (very small) Vim plugin
called ListToggle [16] (which also makes it possible to change the height of
the 'locationlist' window), also written by yours truly.

-------------------------------------------------------------------------------
                                 *youcompleteme-writing-new-semantic-completers*
Writing New Semantic Completers ~

You have two options here: writing an 'omnifunc' for Vim's omnicomplete system
that YCM will then use through its omni-completer, or a custom completer for
YCM using the Completer API [17].

Here are the differences between the two approaches:

 - You have to use VimScript to write the omnifunc, but get to use Python to
   write for the Completer API; this by itself should make you want to use the
   API.

 - The Completer API is a much more powerful way to integrate with YCM and it
   provides a wider set of features. For instance, you can make your Completer
   query your semantic back-end in an asynchronous fashion, thus not blocking
   Vim's GUI thread while your completion system is processing stuff. This is
   impossible with VimScript. All of YCM's completers use the Completer API.

 - Performance with the Completer API is better since Python executes faster
   than VimScript.

If you want to use the 'omnifunc' system, see the relevant Vim docs with ':h
complete-functions'. For the Completer API, see the API docs [17].

If you want to upstream your completer into YCM's source, you should use the
Completer API.

===============================================================================
                                                        *youcompleteme-commands*
Commands ~

-------------------------------------------------------------------------------
The *YcmForceCompileAndDiagnostics* command

Calling this command will force YCM to immediately recompile your file and
display any new diagnostics it encounters. Do note that recompilation with
this command may take a while and during this time the Vim GUI will be
blocked.

You may want to map this command to a key; try putting 'nnoremap <F5>
:YcmForceCompileAndDiagnostics<CR>' in your vimrc.

-------------------------------------------------------------------------------
The *YcmDiags* command

Calling this command will fill Vim's 'locationlist' with errors or warnings if
any were detected in your file and then open it.

A better option would be to use Syntastic which will keep your 'locationlist'
up to date automatically and will also show error/warning notifications in
Vim's gutter.

-------------------------------------------------------------------------------
The *YcmShowDetailedDiagnostic* command

This command shows the full diagnostic text when the user's cursor is on the
line with the diagnostic.

-------------------------------------------------------------------------------
The *YcmDebugInfo* command

This will print out various debug information for the current file. Useful to
see what compile commands will be used for the file if you're using the
semantic completion engine.

-------------------------------------------------------------------------------
The *YcmCompleter* command

This command can be used to invoke completer-specific commands. If the first
argument is of the form 'ft=...' the completer for that file type will be used
(for example 'ft=cpp'), else the native completer of the current buffer will
be used. Call |YcmCompleter| without further arguments for information about
the commands you can call for the selected completer.

===============================================================================
                                                         *youcompleteme-options*
Options ~

All options have reasonable defaults so if the plug-in works after
installation you don't need to change any options. These options can be
configured in your vimrc script [12] by including a line like this:
>
    let g:ycm_min_num_of_chars_for_completion = 1

Note that after changing an option in your vimrc script [12] you have to
restart Vim for the changes to take effect.

-------------------------------------------------------------------------------
The *g:ycm_min_num_of_chars_for_completion* option

This option controls the number of characters the user needs to type before
completion suggestions are triggered. For example, if the option is set to
'2', then when the user types a second alphanumeric character after a
whitespace character, completion suggestions will be triggered.

Default: '2'
>
    let g:ycm_min_num_of_chars_for_completion = 2

-------------------------------------------------------------------------------
The *g:ycm_filetype_whitelist* option

This option controls for which Vim filetypes (see ':h filetype') should YCM be
turned on. The option value should be a Vim dictionary with keys being
filetype strings (like 'python', 'cpp' etc) and values being unimportant (the
dictionary is used like a hash set, meaning that only the keys matter).

The '*' key is special and matches all filetypes. By default, the whitelist
contains only this '*' key.

YCM also has a |g:ycm_filetype_blacklist| option that lists filetypes for
which YCM shouldn't be turned on. YCM will work only in filetypes that both
the whitelist and the blacklist allow (the blacklist "allows" a filetype by
not having it as a key).

For example, let's assume you want YCM to work in files with the 'cpp'
filetype. The filetype should then be present in the whitelist either directly
('cpp' key in the whitelist) or indirectly through the special '*' key. It
should not be present in the blacklist.

Filetypes that are blocked by the either of the lists will be completely
ignored by YCM, meaning that neither the identifier-based completion engine
nor the semantic engine will operate in them.

You can get the filetype of the current file in Vim with ':set ft?'.

Default: '{'*' : 1}'
>
    let g:ycm_filetype_whitelist = { '*': 1 }

-------------------------------------------------------------------------------
The *g:ycm_filetype_blacklist* option

This option controls for which Vim filetypes (see ':h filetype') should YCM be
turned off. The option value should be a Vim dictionary with keys being
filetype strings (like 'python', 'cpp' etc) and values being unimportant (the
dictionary is used like a hash set, meaning that only the keys matter).

See the |g:ycm_filetype_whitelist| option for more details on how this works.

Default: '{'notes': 1, 'markdown': 1, 'text': 1}'
>
    let g:ycm_filetype_blacklist = {
          \ 'notes' : 1,
          \ 'markdown' : 1,
          \ 'text' : 1,
          \}

-------------------------------------------------------------------------------
The *g:ycm_filetype_specific_completion_to_disable* option

This option controls for which Vim filetypes (see ':h filetype') should the
YCM semantic completion engine be turned off. The option value should be a Vim
dictionary with keys being filetype strings (like 'python', 'cpp' etc) and
values being unimportant (the dictionary is used like a hash set, meaning that
only the keys matter). The listed filetypes will be ignored by the YCM
semantic completion engine, but the identifier-based completion engine will
still trigger in files of those filetypes.

Note that even if semantic completion is not turned off for a specific
filetype, you will not get semantic completion if the semantic engine does not
support that filetype.

You can get the filetype of the current file in Vim with ':set ft?'.

Default: '{}'
>
    let g:ycm_filetype_specific_completion_to_disable = {}

-------------------------------------------------------------------------------
The *g:ycm_allow_changing_updatetime* option

When this option is set to '1', YCM will change the 'updatetime' Vim option to
'2000' (see ':h updatetime'). This may conflict with some other plugins you
have (but it's unlikely). The 'updatetime' option is the number of
milliseconds that have to pass before Vim's 'CursorHold' (see ':h CursorHold')
event fires. YCM runs the completion engines' "file comprehension" systems in
the background on every such event; the identifier-based engine collects the
identifiers whereas the semantic engine compiles the file to build an AST.

The Vim default of '4000' for 'updatetime' is a bit long, so YCM reduces this.
Set this option to '0' to force YCM to leave your 'updatetime' setting alone.

Default: '1'
>
    let g:ycm_allow_changing_updatetime = 1

-------------------------------------------------------------------------------
The *g:ycm_complete_in_comments_and_strings* option

When this option is set to '1', YCM will show the completion menu even when
typing inside strings and comments.

Default: '0'
>
    let g:ycm_complete_in_comments_and_strings = 0

-------------------------------------------------------------------------------
The *g:ycm_collect_identifiers_from_comments_and_strings* option

When this option is set to '1', YCM's identifier completer will also collect
identifiers from strings and comments. Otherwise, the text in comments and
strings will be ignored.

Default: '0'
>
    let g:ycm_collect_identifiers_from_comments_and_strings = 0

-------------------------------------------------------------------------------
The *g:ycm_add_preview_to_completeopt* option

When this option is set to '1', YCM will add the 'preview' string to Vim's
'completeopt' option (see ':h completeopt'). If your 'completeopt' option
already has 'preview' set, there will be no effect. You can see the current
state of your 'completeopt' setting with ':set completeopt?' (yes, the
question mark is important).

When 'preview' is present in 'completeopt', YCM will use the 'preview' window
at the top of the file to store detailed information about the current
completion candidate (but only if the candidate came from the semantic
engine). For instance, it would show the full function prototype and all the
function overloads in the window if the current completion is a function name.

Default: '0'
>
    let g:ycm_add_preview_to_completeopt = 0

-------------------------------------------------------------------------------
The *g:ycm_autoclose_preview_window_after_completion* option

When this option is set to '1', YCM will auto-close the 'preview' window after
the user accepts the offered completion string. If there is no 'preview'
window triggered because there is no 'preview' string in 'completeopt', this
option is irrelevant. See the |g:ycm_add_preview_to_completeopt| option for
more details.

Default: '0'
>
    let g:ycm_autoclose_preview_window_after_completion = 0

-------------------------------------------------------------------------------
The *g:ycm_max_diagnostics_to_display* option

This option controls the maximum number of diagnostics shown to the user when
errors or warnings are detected in the file. This option is only relevant if
you are using the semantic completion engine and have installed the version of
the Syntastic plugin that supports YCM.

Default: '30'
>
    let g:ycm_max_diagnostics_to_display = 30

-------------------------------------------------------------------------------
The *g:ycm_key_list_select_completion* option

This option controls the key mappings used to select the first completion
string. Invoking any of them repeatedly cycles forward through the completion
list.

Some users like adding '<Enter>' to this list.

Default: '['<TAB>', '<Down>']'
>
    let g:ycm_key_list_select_completion = ['<TAB>', '<Down>']

-------------------------------------------------------------------------------
The *g:ycm_key_list_previous_completion* option

This option controls the key mappings used to select the previous completion
string. Invoking any of them repeatedly cycles backwards through the
completion list.

Note that one of the defaults is '<S-TAB>' which means Shift-TAB. That mapping
will probably only work in GUI Vim (Gvim or MacVim) and not in plain console
Vim because the terminal usually does not forward modifier key combinations to
Vim.

Default: '['<S-TAB>', '<Up>']'
>
    let g:ycm_key_list_previous_completion = ['<S-TAB>', '<Up>']

-------------------------------------------------------------------------------
The *g:ycm_key_invoke_completion* option

This option controls the key mapping used to invoke the completion menu for
semantic completion. By default, semantic completion is trigged automatically
after typing '.', '->' and '::' in insert mode (if semantic completion support
has been compiled in). This key mapping can be used to trigger semantic
completion anywhere. Useful for searching for top-level functions and classes.

Note that the default of '<C-Space>' means Ctrl-Space. Also note that the
default mapping will probably only work in GUI Vim (Gvim or MacVim) and not in
plain console Vim because the terminal usually does not forward modifier key
combinations to Vim.

Setting this option to an empty string will make sure no mapping is created.

Default: '<C-Space>'
>
    let g:ycm_key_invoke_completion = '<C-Space>'

-------------------------------------------------------------------------------
The *g:ycm_key_detailed_diagnostics* option

This option controls the key mapping used to show the full diagnostic text
when the user's cursor is on the line with the diagnostic. It basically calls
':YcmShowDetailedDiagnostic'.

Setting this option to an empty string will make sure no mapping is created.

Default: '<leader>d'
>
    let g:ycm_key_detailed_diagnostics = '<leader>d'

-------------------------------------------------------------------------------
The *g:ycm_global_ycm_extra_conf* option

Normally, YCM searches for a '.ycm_extra_conf.py' file for compilation flags
(see the User Guide for more details on how this works). This option specifies
a fallback path to a config file which is used if no '.ycm_extra_conf.py' is
found.

You can place such a global file anywhere in your filesystem.

Default: ''
>
    let g:ycm_global_ycm_extra_conf = ''

-------------------------------------------------------------------------------
The *g:ycm_confirm_extra_conf* option

When this option is set to '1' YCM will ask once per '.ycm_extra_conf.py' file
if it is safe to be loaded. This is to prevent execution of malicious code
from a '.ycm_extra_conf.py' file you didn't write.

Default: '1'
>
    let g:ycm_confirm_extra_conf = 1

-------------------------------------------------------------------------------
The *g:ycm_extra_conf_globlist* option

This option is a list that may contain several globbing patterns. If a pattern
starts with a '!' all '.ycm_extra_conf.py' files matching that pattern will be
blacklisted, that is they won't be loaded and no confirmation dialog will be
shown. If a pattern does not start with a '!' all files matching that pattern
will be whitelisted. Note that this option is not used when confirmation is
disabled using |g:ycm_confirm_extra_conf| and that items earlier in the list
will take precedence over the later ones.

Rules:

 - '*' matches everything

 - '?' matches any single character

 - '[seq]' matches any character in seq

 - '[!seq]' matches any char not in seq

Example:
>
    let g:ycm_extra_conf_globlist = ['~/dev/*','!~/*']

 - The first rule will match everything contained in the '~/dev' directory so
   '.ycm_extra_conf.py' files from there will be loaded.

 - The second rule will match everything in the home directory so a
   '.ycm_extra_conf.py' file from there won't be loaded.

 - As the first rule takes precedence everything in the home directory
   excluding the '~/dev' directory will be blacklisted.

Default: '[]'
>
    let g:ycm_extra_conf_globlist = []

-------------------------------------------------------------------------------
The *g:ycm_semantic_triggers* option

This option controls the character-based triggers for the various semantic
completion engines. The option holds a dictionary of key-values, where the
keys are Vim's filetype strings delimited by commas and values are lists of
strings, where the strings are the triggers.

A "trigger" is a sequence of one or more characters that trigger semantic
completion when typed. For instance, C++ ('cpp' filetype) has '.' listed as a
trigger. So when the user types 'foo.', the semantic engine will trigger and
serve 'foo''s list of member functions and variables. Since C++ also has '->'
listed as a trigger, the same thing would happen when the user typed 'foo->'.

Default: '[see next line]'
>
    let g:ycm_semantic_triggers =  {
      \   'c' : ['->', '.'],
      \   'objc' : ['->', '.'],
      \   'cpp,objcpp' : ['->', '.', '::'],
      \   'perl' : ['->'],
      \   'php' : ['->', '::'],
      \   'cs,java,javascript,d,vim,ruby,python,perl6,scala,vb,elixir,go' : ['.'],
      \   'lua' : ['.', ':'],
      \   'erlang' : [':'],
      \ }

===============================================================================
                                                             *youcompleteme-faq*
FAQ ~

-------------------------------------------------------------------------------
I get a linker warning regarding *libpython* on Mac when compiling YCM

If the warning is 'ld: warning: path '/usr/lib/libpython2.7.dylib' following
-L not a directory', then feel free to ignore it; it's caused by a limitation
of CMake and is not an issue. Everything should still work fine.

-------------------------------------------------------------------------------
I get a weird window at the top of my file when I use the semantic engine ~

This is Vim's 'preview' window. Vim uses it to show you extra information
about something if such information is available. YCM provides Vim with such
extra information. For instance, when you select a function in the completion
list, the 'preview' window will hold that function's prototype and the
prototypes of any overloads of the function. It will stay there after you
select the completion so that you can use the information about the parameters
and their types to write the function call.

If you would like this window to auto-close after you select a completion
string, set the |g:ycm_autoclose_preview_window_after_completion| option to
'1' in your 'vimrc' file.

If you don't want this window to ever show up, add 'set completeopt-=preview'
to your 'vimrc'. Also make sure that the |g:ycm_add_preview_to_completeopt|
option is set to '0'.

-------------------------------------------------------------------------------
It appears that YCM is not working ~

In Vim, run ':messages' and carefully read the output. YCM will echo messages
to the message log if it encounters problems. It's likely you misconfigured
something and YCM is complaining about it.

Also, you may want to run the ':YcmDebugInfo' command; it will make YCM spew
out various debugging information, including the compile flags for the file if
the file is a C-family language file and you have compiled in Clang support.

-------------------------------------------------------------------------------
I cannot get the Syntastic integration to work ~

Try to update your version of Syntastic. At the time of writing (Jan 2013),
the YCM integration is very recent and it's likely that your version of
Syntastic does not have it.

-------------------------------------------------------------------------------
Sometimes it takes much longer to get semantic completions than normal ~

This means that libclang (which YCM uses for C-family semantic completion)
failed to pre-compile your file's preamble. In other words, there was an error
compiling some of the source code you pulled in through your header files. I
suggest calling the ':YcmDiags' command to see what they were (even better,
have Syntastic installed and call ':lopen').

Bottom line, if libclang can't pre-compile your file's preamble because there
were errors in it, you're going to get slow completions because there's no AST
cache.

-------------------------------------------------------------------------------
YCM auto-inserts completion strings I don't want! ~

This means you probably have some mappings that interfere with YCM's internal
ones. Make sure you don't have something mapped to '<C-p>', '<C-x>' or '<C-u>'
(in insert mode).

YCM never selects something for you; it just shows you a menu and the user has
to explicitly select something. If something is being selected automatically,
this means there's a bug or a misconfiguration somewhere.

-------------------------------------------------------------------------------
I get a 'E227: mapping already exists for <blah>' error when I start Vim ~

This means that YCM tried to set up a key mapping but failed because you
already had something mapped to that key combination. The '<blah>' part of the
message will tell you what was the key combination that failed.

Look in the options section and see if which of the default mappings conflict
with your own. Then change that option value to something else so that the
conflict goes away.

-------------------------------------------------------------------------------
I'm trying to use a Homebrew Vim with YCM and I'm getting segfaults ~

Something (I don't know what) is wrong with the way that Homebrew configures
and builds Vim. I recommend using MacVim [5]. Even if you don't like the
MacVim GUI, you can use the Vim binary that is inside the MacVim.app package
(it's 'MacVim.app/Contents/MacOS/Vim') and get the Vim console experience.

-------------------------------------------------------------------------------
I have a Homebrew Python and/or MacVim; can't compile/SIGABRT when starting ~

You should probably run 'brew rm python; brew install python' to get the
latest fixes that should make YCM work with such a configuration. Also rebuild
Macvim then. If you still get problems with this, see issue #18 [18] for
suggestions.

-------------------------------------------------------------------------------
I get 'LONG_BIT definition appears wrong for platform' when compiling ~

Look at the output of your CMake call. There should be a line in it like the
following (with '.dylib' in place of '.so' on a Mac):

'-- Found PythonLibs: /usr/lib/libpython2.7.so (Required is at least version
"2.5")'

That would be the correct output. An example of incorrect output would be the
following:

'-- Found PythonLibs: /usr/lib/libpython2.7.so (found suitable version
"2.5.1", minimum required is "2.5")'

Notice how there's an extra bit of output there, the 'found suitable version
"<version>"' part, where '<version>' is not the same as the version of the
dynamic library. In the example shown, the library is version 2.7 but the
second string is version '2.5.1'.

This means that CMake found one version of Python headers and a different
version for the library. This is wrong. It can happen when you have multiple
versions of Python installed on your machine.

You should probably add the following flags to your cmake call (again, 'dylib'
instead of 'so' on a Mac):

'-DPYTHON_INCLUDE_DIR=/usr/include/python2.7 -DPYTHON_LIBRARY=/usr/lib/libpython2.7.so'

This will force the paths to the Python include directory and the Python
library to use. You may need to set these flags to something else, but you
need to make sure you use the same version of Python that your Vim binary is
built against, which is highly likely to be the system's default Python.

-------------------------------------------------------------------------------
I get 'Vim: Caught deadly signal SEGV' on Vim startup ~

This can happen on some Linux distros. If you encounter this situation, run
Vim under 'gdb'. You'll probably see something like this in the output when
Vim crashes:

'undefined symbol: clang_CompileCommands_dispose'

This means that Vim is trying to load a 'libclang.so' that is too old. You
need at least a 3.2 libclang. Some distros ship with a system 'libclang.so'
that identifies itself as 3.2 but is not; it was cut from the upstream sources
before the official 3.2 release and some API changes (like the addition of the
CompileCommands API) were added after their cut.

So just go through the installation guide and make sure you are using a
correct 'libclang.so'. I recommend downloading prebuilt binaries from
llvm.org.

-------------------------------------------------------------------------------
Why isn't YCM just written in plain VimScript, FFS? ~

Because of the identifier completion engine and subsequence-based filtering.
Let's say you have many dozens of files open in a single Vim instance (I often
do); the identifier-based engine then needs to store thousands (if not tens of
thousands) of identifiers in its internal data-structures. When the user
types, YCM needs to perform subsequence-based filtering on all of those
identifiers (every single one!) in less than 10 milliseconds.

I'm sorry, but that level of performance is just plain impossible to achieve
with VimScript. I've tried, and the language is just too slow. No, you can't
get acceptable performance even if you limit yourself to just the identifiers
in the current file and simple prefix-based fitering.

-------------------------------------------------------------------------------
Why does YCM demand such a recent version of Vim? ~

During YCM's development several show-stopper bugs where encountered in Vim.
Those needed to be fixed upstream (and were). A few months after those bugs
were fixed, Vim trunk landed the 'pyeval()' function which improved YCM
performance even more since less time was spent serializing and deserializing
data between Vim and the embedded Python interpreter. A few critical bugfixes
for 'pyeval()' landed in Vim 7.3.584 (and a few commits before that).

-------------------------------------------------------------------------------
I get annoying messages in Vim's status area when I type ~

If you're referring to the 'User defined completion <bla bla> back at
original' and similar, then sadly there's no fix for those. Vim will emit them
no matter how hard I try to silence them.

You'll have to learn to ignore them. It's a shitty "solution", I know.

-------------------------------------------------------------------------------
Nasty bugs happen if I have the *vim-autoclose* plugin installed

Use the delimitMate [19] plugin instead. It does the same thing without
conflicting with YCM.

===============================================================================
                                                         *youcompleteme-contact*
Contact ~

If you have questions, bug reports, suggestions, etc. please use the issue
tracker [20]. The latest version is available at http://valloric.github.com/YouCompleteMe/.

The author's homepage is http://val.markovic.io.

===============================================================================
                                                         *youcompleteme-license*
License ~

This software is licensed under the GPL v3 license [21]. Copyright 2012
Strahinja Val Markovic <val@markovic.io>.

===============================================================================
                                                      *youcompleteme-references*
References ~

[1] http://clang.llvm.org/
[2] http://i.imgur.com/0OP4ood.gif
[3] http://en.wikipedia.org/wiki/Subsequence
[4] https://github.com/scrooloose/syntastic
[5] http://code.google.com/p/macvim/#Download
[6] https://github.com/gmarik/vundle#about
[7] http://mxcl.github.com/homebrew/
[8] http://www.cmake.org/cmake/resources/software.html
[9] https://github.com/Valloric/YouCompleteMe/wiki/Building-Vim-from-source
[10] https://github.com/Valloric/YouCompleteMe/wiki/Windows-Installation-Guide
[11] https://github.com/tpope/vim-pathogen#pathogenvim
[12] http://vimhelp.appspot.com/starting.txt.html#vimrc
[13] http://llvm.org/releases/download.html#3.2
[14] https://github.com/Valloric/YouCompleteMe/blob/master/cpp/ycm/.ycm_extra_conf.py
[15] http://clang.llvm.org/docs/JSONCompilationDatabase.html
[16] https://github.com/Valloric/ListToggle
[17] https://github.com/Valloric/YouCompleteMe/blob/master/python/completers/completer.py
[18] https://github.com/Valloric/YouCompleteMe/issues/18
[19] https://github.com/Raimondi/delimitMate
[20] https://github.com/Valloric/YouCompleteMe/issues?state=open
[21] http://www.gnu.org/copyleft/gpl.html

vim: ft=help