Check modules represent the checks which are run during Credo's analysis.

Example:

defmodule MyCheck do
  use Credo.Check, category: :warning, base_priority: :high

  def run(%SourceFile{} = source_file, params) do
    #
  end
end

The check can be configured by passing the following options to use Credo.Check:

• :base_priority Sets the checks's base priority (:low, :normal, :high, :higher or :ignore).

• :category Sets the check's category (:consistency, :design, :readability, :refactor or :warning).

• :elixir_version Sets the check's version requirement for Elixir (defaults to >= 0.0.1).

• :explanations Sets explanations displayed for the check, e.g.

    [
      check: "...",
      params: [
        param1: "Your favorite number",
        param2: "Online/Offline mode"
      ]
    ]

• :param_defaults Sets the default values for the check's params (e.g. [param1: 42, param2: "offline"])

• :tags Sets the tags for this check (list of atoms, e.g. [:tag1, :tag2])

Please also note that these options to use Credo.Check are just a convenience to implement the Credo.Check behaviour. You can implement any of these by hand:

defmodule MyCheck do
  use Credo.Check

  def category, do: :warning

  def base_priority, do: :high

  def explanations do
    [
      check: "...",
      params: [
        param1: "Your favorite number",
        param2: "Online/Offline mode"
      ]
    ]
  end

  def param_defaults, do: [param1: 42, param2: "offline"]

  def run(%SourceFile{} = source_file, params) do
    #
  end
end

The run/2 function of a Check module takes two parameters: a source file and a list of parameters for the check. It has to return a list of found issues.