Bylaw.Credo.Check.Elixir.RejectCount (bylaw_credo v0.1.0-alpha.1)

Basics

This check has a base priority of high and works with any version of Elixir.

Explanation

Use Enum.count/2 instead of rejecting items and then counting the remaining list.

Examples

Avoid:

  users
  |> Enum.reject(&(&1.status == :inactive))
  |> Enum.count()

Prefer:

  Enum.count(users, &(&1.status != :inactive))

Notes

Enum.reject/2 builds an intermediate list just so Enum.count/1 can count it. The callback is also written in the negative, which makes the kept values less obvious.

Enum.count/2 performs the count in one pass without allocating the rejected list, and the predicate describes the values being counted.

This check uses static AST analysis, so it favors clear source-level patterns over runtime behavior.

Options

This check has no check-specific options. Configure it with an empty option list.

Usage

Add this check to Credo's checks: list in .credo.exs:

%{
  configs: [
    %{
      name: "default",
      checks: [
        {Bylaw.Credo.Check.Elixir.RejectCount, []}
      ]
    }
  ]
}

Check-Specific Parameters

There are no specific parameters for this check.

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.