elvis

Command-line interface for Elvis, the Erlang style reviewer.

Contact Us

If you find any bugs or have a problem while using this library, please open an issue in this repo (or a pull request :)).

Installation

1. Clone the repo
2. rebar3 compile

Usage

In any elvis-enabled product, elvis rock will trigger a rule check.

Script

elvis can be turned into a script by executing rebar3 escriptize. This will generate an elvis self-contained executable script, from which you can get help by typing elvis help. A list of available commands can be shown using the --commands option (i.e. elvis --commands).

To run elvis from the terminal use the rock command (i.e. elvis rock). There's no need to specify a configuration file path if you have an elvis.config file in the same location where you are executing the script, otherwise a configuration file can be specified through the use of the --config (or just -c) option.

elvis rock --config config/elvis.config

In 0.3.0 a new option was introduced in order to run elvis checks only on the source files that have changed since a particular branch of commit. Example usage would be elvis git-branch origin/HEAD.

Benefits

• Enables consistency in style across all your code base.
• Encourages the development team to sit down and talk about code conventions.
• Allows continuous monitoring of code quality.
• Helps developers avoid repeated mistakes that can be automatically detected.
• Provides homogenisation among the different projects in a company, therefore facilitating project switching for developers and as well allowing easier code sharing between projects

Webhook

There's also a way to use elvis as a GitHub webhook for pull request (PR) events by calling the elvis_webhook:event/1 function. This will add a comment in each file and rule that is broken, analyzing only the files associated with the PR.

Running the webhook on your servers

Since GitHub's API needs a valid user and password to allow the creation of reviews on PRs, the parameters github_user and github_password need to be added to elvis's configuration and also the credentials used must be from an admin of the repo or someone with permissions for requesting changes on PRs.

The webhook/1 function takes a map containing the keys headers and body, whose values should be the map of headers and the body from the GitHub's event request.

Headers = #{<<"X-GitHub-Event">>, <<"pull_request">>},
Body = <<"{}">>, %% JSON data form GitHub's event.
Request = #{headers => Headers, body => Body},
elvis:webhook(Request).

Git hook

elvis can also be used as a git pre-commit hook using the git-hook command, just use something like the following as your pre-commit script:

#!/bin/sh
#
# Runs elvis rules to staged files where applicable.

elvis git-hook

As the comment states, elvis will search for files that match the filter of each rule group (see configuration) among the staged files, get their staged content and run the rules specified in the configuration. If any rule fails then elvis exits with a non-zero code, which signals git that the commit shouldn't be made.

Make sure your pre-commit hook script is executable (i.e. by running chmod +x pre-commit), otherwise git won't be able to run it.

Erlang Shell

If you only need to use elvis in the Erlang shell you might want to consider only including the elvis_core library as a dependency.

Configuration

To provide a default configuration for elvis you should either create an elvis.config file located in the root directory or set the following environment values in your configuration file:

[
 {
   elvis,
   [
    {config, [...]},
    {output_format, plain},

    %% Only necessary for the 'webhook' functionality
    {github_user, "user"},
    {github_password, "password"}
   ]
 }
].

The config and output_format are explained in elvis_core.

The GitHub configuration parameters github_user and github_password are required only when elvis is used as a webhook.

elvis.config

In your elvis.config file you can setup which rules should be applied, on what files and in which directories to do it.

The configuration is in Erlang format, it is not that hard to write but it is easier if you use the elvis.config file in this reposiotry as a template.

In the elvis.config file you create an elvis config where for a set of directories, you want to run a ruleset (or specific rules) on a set of files.

For example, configure to check all erlang files under the src directory using the ruleset erl_files:

[
 {
   elvis,
   [
    {config,
     [#{dirs => ["src"],
        filter => "*.erl",
        ruleset => erl_files
       }
     ]
    }
   ]
 }
].

You can use four different rulesets erl_files, makefiles, rebar_config or elvis_config.

Implemented Rules

A reference of all rules implemented in Elvis can be found in this wiki page: Rules.

User Defined Rules

If you have implemented an Elvis rule that's in your local repo or in one of your dependencies, you can add this rule to your elvis.config file and tell Elvis where to find the .beam that contains the compiled rule using the --code-path (-p) option.

For example if the rule is in one of your deps, you could run Elvis in the following way:

elvis rock -p deps/elvis_rules/ebin -c elvis.config

Dependencies

• Erlang/OTP 18+
• git

References

Inspired on HoundCI