CodeStyle

Shared deterministic Elixir code-quality policy and Credo checks.

CodeStyle composes a deliberately curated policy from Credo, focused third-party check providers, migration safety, and a small number of custom checks. Adding a provider dependency does not enable its full rule set: every enabled check is allowlisted explicitly and covered by policy tests.

CodeStyle is intended to be used alongside ExDNA and Styler. Those tools are not bundled with this library and should be configured separately in consuming projects.

Installation

Add code_style to a consuming Mix project:

{:code_style, "~> 0.2.0", only: [:dev, :test], runtime: false}

Then load the Credo plugin in .credo.exs:

%{
  configs: [
    %{
      name: "default",
      plugins: [{CodeStyle, []}]
    }
  ]
}

The plugin registers the shared Credo policy, curated Jump.CredoChecks, CredoMox, ForgeCredoChecks and ExSlop checks, ExcellentMigrations migration safety, and the custom checks below. It does not override Credo's file discovery; consuming projects can define their own files configuration when needed.

Policy model

A check belongs in the shared policy when its evidence is deterministic and the rule is broadly applicable across Elixir repositories. Repository-specific architecture rules remain with the repository that owns that architecture.

Third-party checks are selected individually. Dependency upgrades therefore do not silently expand the policy.

Custom Checks

• CodeStyle.Check.Warning.EnvironmentVariableAccess keeps OS environment access at the configuration boundary by reporting System.get_env/* and System.fetch_env!/1 from lib/ while allowing configuration under config/.
• CodeStyle.Check.Warning.RepoInsideLoop flags direct Repo operations that can execute once per element across collection and concurrency boundaries.

Development

Run the package checks with Mix:

mix check