AshCredo.Check.Warning.RedundantValidation (ash_credo v0.17.1)

Basics

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

Explanation

Flags validate present(...) where every referenced field is an attribute that already has allow_nil? false. The attribute constraint guarantees presence on its own, so the validation can only ever duplicate an error the changeset already carries. Straight from Ash's usage rules: avoid validations that duplicate attribute constraints.

# Bad - allow_nil? false already rejects nil
attributes do
  attribute :name, :string, allow_nil?: false
end

actions do
  create :create do
    validate present(:name)
  end
end

# Good - let the attribute constraint handle it
attributes do
  attribute :name, :string, allow_nil?: false
end

Fields an action opens up via allow_nil_input are skipped: there the attribute may legitimately be nil at validation time (for example filled by the data layer during an upsert), so present does add a real constraint.

The check also skips a field when an update or destroy action has a same-named argument. The atomic execution path is the default for those action types (require_atomic? defaults to true), and in that path the built-in present validation validates the argument instead of the attribute. The validation then enforces that the caller supplied the argument, regardless of the attribute constraint.

In the non-atomic path the validation falls back to the attribute when the argument is nil, where it is indeed vacuous. But advising removal would silently drop the atomic-path constraint, so the check stays silent.

Create actions never execute atomically, so a same-named argument on a create does not rescue the validation and no escape applies there. Validations in read and generic actions are not examined either, because present resolves against action arguments there, not attributes.

Requirements

Your project must be compiled before running mix credo. If Ash is not available in the VM running Credo, the check is a no-op and emits a single diagnostic.

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.