elvis-core

Erlang style reviewer core library.

This library includes the mechanism to apply rules to your code and their implementation.

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 :)).

Contributing & Reporting Bugs

If you find a bug or want to contribute to this project please create an issue through the elvis repository. This is where all elvis related work is coordinated.

Usage

As a library

This library implements all the core functionality for the elvis command-line tool. For an example on how to use it please check that project.

Erlang Shell

After adding elvis_core as a dependency to your project and setting up its configuration, you can run it from an Erlang shell in the following two ways.

elvis_core:rock().
%%+ # src/elvis_core.erl [OK]
%%+ # src/elvis_result.erl [OK]
%%+ # src/elvis_style.erl [OK]
%%+ # src/elvis_utils.erl [OK]
%%= ok

This will try to load the configuration for elvis_core specified in an elvis.config located in the current directory. If no configuration is found invalid_config will be thrown.

To start the application in the shell enter the following command:

application:start(elvis_core).
%%= ok

Another option for using elvis_core from the shell is explicitly providing a configuration as an argument to rock/1:

Config = [#{dirs => ["src"], filter => "*.erl", rules => []}],
elvis_core:rock(Config).
%%+ # src/elvis_core.erl [OK]
%%+ # src/elvis_result.erl [OK]
%%+ # src/elvis_style.erl [OK]
%%+ # src/elvis_utils.erl [OK]
%%= ok

IMPORTANT: Config should have a valid format, but since this is a project under development the definition for valid format is still a work in progress. If the configuration format changes though, the example configuration files and the documentation in this README will be updated.

We have only presented results where all files were well-behaved (respect all the rules), so here's an example of how it looks when files break some of the rules:

# ../../test/examples/fail_line_length.erl [FAIL]
  - line_length
    - Line 14 is too long: "    io:format(\"This line is 81 characters long and should be detected, yeah!!!\").".
    - Line 20 is too long: "    io:format(\"This line is 90 characters long and should be detected!!!!!!!!!!!!!!!!!!\").".
# ../../test/examples/fail_no_tabs.erl [FAIL]
  - no_tabs
    - Line 6 has a tab at column 0.
    - Line 15 has a tab at column 0.
# ../../test/examples/small.erl [OK]

Configuration

To provide a default configuration you should create an elvis.config file located in the root directory:

[
 {
   elvis,
   [
    {config,
     [#{dirs => ["src"],
        include_dirs => ["include"],
        filter => "*.erl",
        ruleset => erl_files
       },
      #{dirs => ["."],
        filter => "Makefile",
        ruleset => makefiles
       },
      #{dirs => ["."],
        filter => "rebar.config",
        ruleset => rebar_config
       },
      #{dirs => ["."],
        filter => "elvis.config",
        ruleset => elvis_config
       }
     ]
    },
    %% Optional to select the output format, the default is colors
    {output_format, plain},
    %% Only necessary for the 'webhook' functionality
    {github_user, "user"},
    {github_password, "password"}
   ]
 }
].

The include_dirs key is just a list of folders ([string()]) where to search for header files.

The dirs key is a list that indicates where elvis should look for the files that match filter, which will be run through each of the default rules in the specified ruleset, which is an atom. If you want to override the default rules for a given ruleset you need to specify them in a rules key which is a list of items with the following structure {Module, Function, RuleConfig} or {Module, Function} if the rule takes no configuration values. You can also disable certain rules if you want to just by specifying the rule in the rules key and passing disable as its third parameter.

IMPORTANT: disable will only work if you also provided a ruleset as shown above.

Let's say you like your files to have a maximum of 90 characters per line and also you like to use tabs instead of spaces, so you need to override erl_files ruleset default rules as follows:

#{dirs => ["src"],
  filter => "*.erl",
  rules => [{elvis_style, line_length, #{limit => 90}}, %% change default line_length limit from 100 to 90
            {elvis_style, no_tabs, disable}], %% disable no_tabs rule
  ruleset => erl_files
},

You can also ignore modules at a check level or at a ruleset (group of checks) level:

• at check level by setting the ignore parameter in the rule you want to skip, e.g:

  {elvis_style, no_debug_call, #{ignore => [elvis, elvis_utils]}}

  There we are telling elvis to ignore elvis and elvis_utils modules when running no_debug_call check.

• at ruleset level by setting the ignore group level option for the group you want to skip, e.g:

  #{dirs => ["src"],
    filter => "*.erl",
    ruleset => erl_files,
    ignore => [module1, module4]
   }

  With this configuration, none of the checks for erl_files would be applied to module1.erl and module4.erl files.

The implementation of a rule is just a function that takes 3 arguments: elvis's config entry from its configuration; the file to be analyzed; and a configuration map specified for the rule. This means you can define rules of your own as long as the functions that implement them respect this arity.

You can find the default elvis configuration file at config/elvis.config.

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

Implemented Rules

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

References

Inspired by HoundCI