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https://github.com/racer-rust/emacs-racer

Racer support for Emacs
https://github.com/racer-rust/emacs-racer

completion-racer emacs racer rust

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Racer support for Emacs

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# Racer for Emacs

[![MELPA](http://melpa.org/packages/racer-badge.svg)](http://melpa.org/#/racer)

[![MELPA Stable](http://stable.melpa.org/packages/racer-badge.svg)](http://stable.melpa.org/#/racer)

[![Coverage Status](https://coveralls.io/repos/github/racer-rust/emacs-racer/badge.svg?branch=master)](https://coveralls.io/github/racer-rust/emacs-racer?branch=master)



This is the official Emacs package for

[Racer](http://github.com/phildawes/racer).



**Table of Contents**



- [Racer for Emacs](#racer-for-emacs)

    - [Completion](#completion)

    - [Find Definitions](#find-definitions)

    - [Describe Functions and Types](#describe-functions-and-types)

    - [Installation](#installation)

        - [Testing your setup](#testing-your-setup)

    - [Tests](#tests)



## Completion



racer.el supports code completion of variables, functions and modules.



![racer completion screenshot](images/racer_completion.png)



You can also press F1 to pop up a help buffer for the current

completion candidate.



Note that due to a

[limitation of racer](https://github.com/phildawes/racer/issues/389),

racer.el cannot offer completion for macros.



## Find Definitions



racer.el can jump to definition of functions and types.



![racer go to definition](images/racer_goto.gif)



You can use M-. to go to the definition, and M-,

to go back.



## Describe Functions and Types



racer.el can show a help buffer based on the docstring of the thing at

point.



![racer completion screenshot](images/racer_help.png)



Use M-x racer-describe to open the help buffer.



## Installation



1. You will need to use a nightly version of rust.

   If you're using rustup, run

   ```

   $ rustup toolchain add nightly

   ```



2. Install [Racer](http://github.com/phildawes/racer) and download the

   source code of Rust:



   ```

   $ rustup component add rust-src

   $ cargo +nightly install racer

   ```



3. Allow Emacs to install packages from MELPA:



   ```el

   (require 'package)

   (add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/"))

   ```



4. Install the Emacs package for Racer: `M-x package-install RET racer RET`



5. Configure Emacs to activate racer when rust-mode starts:

   ```el

   (add-hook 'rust-mode-hook #'racer-mode)

   (add-hook 'racer-mode-hook #'eldoc-mode)

   ```



   For completions, install company with `M-x package-install RET company RET`. A sample configuration:

   ```el



   (add-hook 'racer-mode-hook #'company-mode)



   (require 'rust-mode)

   (define-key rust-mode-map (kbd "TAB") #'company-indent-or-complete-common)

   (setq company-tooltip-align-annotations t)

   ```

   For automatic completions, customize `company-idle-delay` and

   `company-minimum-prefix-length`.



   Racer process may be slow to respond for instance when indexing. You can

   customize `racer-command-timeout` and `racer-eldoc-timeout` to avoid rendering

   your Emacs session unresponsive. Eldoc timeout should be on the lower side and

   defaults to 0.5 seconds. You can probably tweak it down on a fast machine.

   Timeout of `nil` will wait indefinitely.



### Testing your setup



To test **completion**: Open a rust file and try typing ```use

std::io::B``` and press TAB.



To test **go to definition**: Place your cursor over a symbol and press

`M-.` to jump to its definition.



Press `C-x 4 .` to jump to its definition in another window.



Press `C-x 5 .` to jump to its definition in another frame.



Press `M-,` to jump back to the previous cursor location.



If **it doesn't work**, try `M-x racer-debug` to see what command was

run and what output was returned.



## Tests



racer.el includes tests. To run them, you need to install

[Cask](https://github.com/cask/cask), then:



```

$ cask install

$ cask exec ert-runner

```