Custom Credo Checks

This directory contains custom Credo checks specific to the Firezone codebase.

Available Checks

Warning.MissingChangesetFunction

Ensures that Ecto schema modules define a changeset/1 function that accepts an Ecto.Changeset.

Rationale: We expect the caller to be able to pass in an already-created changeset for validation, ensuring a consistent pattern across the codebase.

Exceptions:

• Embedded schemas (using embedded_schema do blocks) typically use changeset/2 instead
• Simple schemas that don't accept user input (like audit logs, processed events, or read-only schemas) may not need a changeset function

Example:

defmodule Portal.Account do
  use Ecto.Schema
  import Ecto.Changeset

  schema "accounts" do
    field :name, :string
    timestamps()
  end

  def changeset(changeset) do
    changeset
    |> validate_required([:name])
    |> validate_length(:name, min: 3, max: 64)
  end
end

Warning.ActionFallbackUsage

Prevents the use of action_fallback macro in controllers. Use explicit error handling with Error.handle/2 instead.

Warning.UnsafeRepoUsage

Restricts direct Portal.Repo calls to specific contexts (Portal.Safe module, seeds, tests, migrations).

Warning.SafeCallsOutsideDatabaseModule

Validates that database functions are properly isolated.

Warning.MissingDatabaseAlias

Ensures proper Portal.Safe aliasing in modules that need it.

Warning.CrossModuleDatabaseCall

Prevents cross-module database operations to maintain proper boundaries.

Running Checks

# Run all Credo checks
mix credo --strict

# Run only custom checks
mix credo --only MissingChangesetFunction

# Run Credo in CI
# Checks are automatically run in the GitHub Actions workflow

Adding New Custom Checks

1. Create a new module in .credo/check/warning/ or .credo/check/consistency/
2. Implement the check following the pattern of existing checks
3. Add the check to .credo.exs in both the requires and checks.enabled sections
4. Test the check on relevant code
5. Document the check in this README