git clone 'git://github.com/abingham/emacs-ycmd.git'


emacs-ycmd is a client for ycmd, the code completion system. It takes care of managing a ycmd server and fetching completions from that server.

emacs-ycmd comprises a core set of functionality for communicating with ycmd as well as integration with emacs completion frameworks like company-mode and auto-complete-mode.

A lot of the concepts behind emacs-ycmd are actually concepts from ycmd itself, so if you feel lost you might read the ycmd documentation and/or the the original YouCompleteMe documentation.


First make sure that ycmd is installed on your system. See the ycmd instructions for more details.

To use ycmd-mode in all supported modes, add the following to your emacs config:

(require 'ycmd)
(add-hook 'after-init-hook #'global-ycmd-mode)

Or add ycmd-mode to a specific supported mode:

(require 'ycmd)
(add-hook 'c++-mode-hook 'ycmd-mode)

Use the variable ycmd-server-command to specify how to run the server. It will typically be something like:

(set-variable 'ycmd-server-command '("python" "/path/to/ycmd/package"))

If you've got a global ycmd configuration, specify that in your emacs configuration by setting ycmd-global-config:

(set-variable 'ycmd-global-config "/path/to/global_config.py")

If you've got project-specific ycmd configurations (almost certainly called .ycm_extra_conf.py), and if you want them automatically loaded by ycmd as needed (which you probably do), then you can whitelist them by adding entries to ycmd-extra-conf-whitelist. For example, this will allow automatic loading of all .ycm_extra_conf.py files anywhere under ~/my_projects

(set-variable 'ycmd-extra-conf-whitelist '("~/my_projects/*"))

Alternatively, you can set ycmd-extra-conf-handler to control how ycmd.el deals with non-whitelisted extra configs. By default this is set to 'ask, meaning it will ask the user each time one is encountered. The other options are 'ignore, in which case the extra config will be ignored, and 'load, in which case the extra config will be loaded.

Now a ycmd server will be automatically launched whenever it's needed. Generally, this means whenever you visit a file with a supported major mode. You should not normally need to manually start or stop a ycmd server.

With a server running, you can now get completions for a point in a file using ycmd-get-completions. This doesn't actually insert the completions; it just fetches them from the server. It's not even an interactive function, so you can't really call it while editing. If you just want to see the possible completions at a point, you can try ycmd-display-completions which will dump a raw completion struct into a buffer. This is more of a debugging tool than anything.

More likely, you'll want to use a completion framework like company-mode to manage the completions for you. Here's how to do that:

(require 'company-ycmd)

After this you can use your standard company-mode keybindings to do completion.

IMPORTANT: Unbuffered output on Windows

There have been some reports that ycmd.el doesn't work on Windows when Python's output is buffered. See, for example, issue #104. This is because we rely on the ycmd server printing out its host and port information in a timely (i.e. unbuffered) manner. We will almost certainly update the defaults for ycmd.el to force unbuffered output.

In any event, if you are facing problems with ycmd not starting and/or hanging Emacs on Windows, try adding -u to your ycmd-server-command. For example: (set-variable 'ycmd-server-command '("c:/path/to/python.exe" "-u" "c:/path/to/ycmd"))

flycheck integration

flycheck-ycmd.el allows you to use ycmd as a backend for flycheck. With this enabled, whenever ycmd parses a file the results will be passed to flycheck for display. This is a really nice way to get quick feedback on problems in your code.

The simple way to enable flycheck integration is to use flycheck-ycmd-setup:

(require 'flycheck-ycmd)

This will make sure that flycheck sees the parse results, and that the flycheck-ycmd backend is enabled.

If for some reason you want to do this manually, the instructions are like this:

(require 'flycheck-ycmd)

;; Make sure the flycheck cache sees the parse results
(add-hook 'ycmd-file-parse-result-hook 'flycheck-ycmd--cache-parse-results)

;; Add the ycmd checker to the list of available checkers
(add-to-list 'flycheck-checkers 'ycmd)

Disabling ycmd-based flycheck for specific modes

If you use flycheck-ycmd-set or otherwise put ycmd at the front of flycheck-checkers, flycheck will use the ycmd checker for every buffer in ycmd-mode. This may not be what you want. For example, even though ycmd supports completion (and, thus, flycheck) for Python, you may wish to use pyflakes for flychecking Python code.

To disable ycmd-based flychecking for specific modes, you can modify the flycheck-disabled-checkers list in your mode hook. For example:

(add-hook 'python-mode-hook (lambda () (add-to-list 'flycheck-disabled-checkers 'ycmd))

With this, the ycmd checker will be ignored in python-mode. Since flycheck-disabled-checkers is buffer-local, the ycmd-based checker will still be available for other modes.

Making flycheck and company work together

In some cases you may see that company and flycheck interfere with one another. You can end up with strange completion artifacts in your buffers. This mostly seems to happen when you run emacs in “terminal mode”, i.e. with emacs -nw.

The short answer for how to deal with this is: (setq flycheck-indication-mode nil)

The slightly longer and probably better answer is: (when (not (display-graphic-p)) (setq flycheck-indication-mode nil))

For a full explanation see the emacs-ycmd defect related to this as well as the root flycheck issue.

next-error integration

emacs-ycmd reports found errors through emacs buttons; to integrate those with next-error prepend something like (require 'ycmd-next-error) before require'ing ycmd (after adding the contrib directory to your load-path).

Making emacs-ycmd quieter

In some common configurations emacs-ycmd can produce lots of messages, and some people find these noisy and distracting. If you're seeing a lot of messages like Contacting host: and you'd like to quiet them, set url-show-status to nil. This can effect non-ycmd-related buffers, so consider using buffer-local settings if this worries you.

You might also see a flurry of messages like this:

REQUEST [error] Error (error) while connecting to
REQUEST [error] Error (error) while connecting to [26 times]

These almost never indicate something you need to be concerned about. To quiet them, you can set ycmd-request-message-level to -1.

See issue #173 for the initial discussion of this topic.

Running tests

emacs-ycmd comes with a number of tests that you can. This is mostly useful for developers. They are built with ert, so you can run them using any technique that ert provides. For example:

(require 'ycmd-test)
(ert-run-tests-interactively "ycmd-test")