Check Parameters

Checks are configured using parameters (short: params).

There are custom params for each check and a set of general params that work for all checks.

Configuration

Checks and their params are configured in Credo's configuration file:

# .credo.exs
%{
  configs: [
    %{
      name: "default",
      checks: [
        {Credo.Check.Consistency.TabsOrSpaces, false},
        {Credo.Check.Design.AliasUsage, if_nested_deeper_than: 2},
      ],
      # files etc.
    }
  ]
}

All checks are configured using a two-element tuple:

{MyApp.CheckModule, params}

MyApp.CheckModule is the module representing the check to be configured (read more about custom checks).

params can be either false, to disable the check ...

# This check won't be part of the analysis
{Credo.Check.Consistency.TabsOrSpaces, false}

... or a keyword list of parameters, used to configure the check:

{Credo.Check.Design.AliasUsage, if_nested_deeper_than: 2}

General params

While params are defined by each check individually, there are a couple of general params provided by Credo, which work the same for each check.

The general params available are:

• :category
• :exit_status
• :files
• :priority
• :tags

:category

Overwrites the category of the check

{Credo.Check.Warning.IExPry, category: :readability}

:exit_status

Overwrites a custom exit status for the check

{Credo.Check.Warning.IoInspect, exit_status: 0}

Read more on exit status in Credo.

:files

Controls which files the check runs on.

This allows for specific files or patterns to be included/excluded for specific checks.

The syntax is the same as for the top-level :files key:

# check included for Elixir files in lib/ only
{Credo.Check.Consistency.ExceptionNames, files: %{included: ["lib/**/*.ex"]}},

# check excluded for a specific file
{Credo.Check.Warning.IExPry, files: %{excluded: ["lib/debug_server.ex"]}},

# check included for all Elixir script files, but excluded for test scripts
{Credo.Check.Warning.IoInspect, files: %{included: ["**/*.exs"], excluded: ["**/*_test.exs"]}},

Please note that these params do not "override" the top-level config, but are applied to the result of the top-level config's resolution.

:priority

Overwrites the priority of the check

{Credo.Check.Warning.IoInspect, priority: :low}

Available priorities are: :low, :normal, :high and :higher.

:tags

Overwrites or appends the tags of the check

# Overwrite all tags for `MyApp.CheckModule`
{MyApp.CheckModule, tags: [:my_tag]}

# OR: append tags to `MyApp.CheckModule`
{MyApp.CheckModule, tags: [:__initial__, :my_tag]}

Tags can then be used to include or exclude checks from the analysis:

# Only run checks tagged `:my_tag` during analysis
$ mix credo --checks-with-tag my_tag

# Exclude all checks tagged `:my_tag` from analysis
$ mix credo --checks-without-tag my_tag