Trogon.Credo

Trogon.Credo is a shared library of Credo checks you depend on instead of copy. It turns the custom check modules that accumulate in a project's .credo/checks/ directory into a versioned Hex package that many repositories can point at.

The package ships check modules and nothing else. Each check lives under the Trogon.Credo.Check.<Category>.<Name> namespace, mirroring Credo's own layout, and is built entirely on Credo's public API so a Credo patch release cannot break it. There is no Credo plugin here, so every consumer enables the checks it wants in its own .credo.exs and leaves the rest out.

Custom Credo checks have no distribution story of their own. A check written for one repository gets copied into the next, then the two drift: a false positive fixed in one copy stays broken in the other, and neither version is tested anywhere. Shipping the checks as a dependency gives them a single source, a test suite, and a version number, so a fix reaches every project that upgrades.

This is for teams running Credo across more than one Elixir repository, and for anyone who has already written a custom check worth keeping. Checks that encode an architectural convention, such as where a layer's modules must live, are parameterized and ship inert, so the conventions stay in each project's configuration while the code that enforces them stays here.

How-to

Enable a check

Add the check module to the checks: %{enabled: [...]} list in your project's .credo.exs:

%{
  configs: [
    %{
      name: "default",
      checks: %{
        enabled: [
          {Trogon.Credo.Check.Warning.ForbiddenImport,
           [modules: [{MyApp.Fixtures, "Call MyApp.Fixtures functions with the full name."}]]}
        ]
      }
    }
  ]
}

Run mix credo as usual and the enabled checks run alongside Credo's built-in ones.

References

Every check documents what it flags and the parameters it accepts in its own module documentation, so the two never drift apart. Browse them under Trogon.Credo.Check in the published documentation, or read one from a project that already depends on the package:

$ mix credo explain Trogon.Credo.Check.Warning.ForbiddenImport